feat(otel): add OpenTelemetry support

pkg/gotenberg/cmd.go

@@ -6,17 +6,16 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log/slog"
 	"os/exec"
 	"strings"
 	"syscall"
-
-	"go.uber.org/zap"
 )
 
 // Cmd wraps an [exec.Cmd].
 type Cmd struct {
 	ctx     context.Context
-	logger  *zap.Logger
+	logger  *slog.Logger
 	process *exec.Cmd
 }
 
@@ -25,13 +24,13 @@ type Cmd struct {
 // children without creating orphans.
 //
 // See https://medium.com/@felixge/killing-a-child-process-and-all-of-its-children-in-go-54079af94773.
-func Command(logger *zap.Logger, binPath string, args ...string) *Cmd {
+func Command(logger *slog.Logger, binPath string, args ...string) *Cmd {
 	cmd := exec.Command(binPath, args...)
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
 
 	return &Cmd{
 		ctx:     nil,
-		logger:  logger.Named(strings.ReplaceAll(binPath, "/", "")),
+		logger:  logger.With(slog.String("logger", strings.ReplaceAll(binPath, "/", ""))),
 		process: cmd,
 	}
 }
@@ -41,7 +40,7 @@ func Command(logger *zap.Logger, binPath string, args ...string) *Cmd {
 // children without creating orphans.
 //
 // See https://medium.com/@felixge/killing-a-child-process-and-all-of-its-children-in-go-54079af94773.
-func CommandContext(ctx context.Context, logger *zap.Logger, binPath string, args ...string) (*Cmd, error) {
+func CommandContext(ctx context.Context, logger *slog.Logger, binPath string, args ...string) (*Cmd, error) {
 	if ctx == nil {
 		return nil, errors.New("nil context")
 	}
@@ -51,7 +50,7 @@ func CommandContext(ctx context.Context, logger *zap.Logger, binPath string, arg
 
 	return &Cmd{
 		ctx:     ctx,
-		logger:  logger.Named(strings.ReplaceAll(binPath, "/", "")),
+		logger:  logger.With(slog.String("logger", strings.ReplaceAll(binPath, "/", ""))),
 		process: cmd,
 	}, nil
 }
@@ -63,7 +62,7 @@ func (cmd *Cmd) Start() error {
 		return fmt.Errorf("pipe unix process output: %w", err)
 	}
 
-	cmd.logger.Debug(fmt.Sprintf("start unix process: %s", strings.Join(cmd.process.Args, " ")))
+	cmd.logger.DebugContext(context.Background(), fmt.Sprintf("start unix process: %s", strings.Join(cmd.process.Args, " ")))
 
 	err = cmd.process.Start()
 	if err != nil {
@@ -110,7 +109,7 @@ func (cmd *Cmd) Exec() (int, error) {
 	case err = <-errChan:
 		errProc := cmd.Kill()
 		if errProc != nil {
-			cmd.logger.Error(errProc.Error())
+			cmd.logger.ErrorContext(context.Background(), errProc.Error())
 		}
 
 		if err == nil {
@@ -125,7 +124,7 @@ func (cmd *Cmd) Exec() (int, error) {
 	case <-cmd.ctx.Done():
 		errProc := cmd.Kill()
 		if errProc != nil {
-			cmd.logger.Error(errProc.Error())
+			cmd.logger.ErrorContext(context.Background(), errProc.Error())
 		}
 
 		return 62, fmt.Errorf("context done: %w", cmd.ctx.Err())
@@ -135,8 +134,7 @@ func (cmd *Cmd) Exec() (int, error) {
 // pipeOutput creates logs entries according to the process stdout and stderr.
 // It does nothing if the logging level is not debug.
 func (cmd *Cmd) pipeOutput() error {
-	checkedEntry := cmd.logger.Check(zap.DebugLevel, "check for debug level before piping unix process output")
-	if checkedEntry == nil {
+	if !cmd.logger.Enabled(context.Background(), slog.LevelDebug) {
 		return nil
 	}
 
@@ -152,12 +150,12 @@ func (cmd *Cmd) pipeOutput() error {
 
 	// logCommandOutput creates logs entries according to a reader
 	// (either stdout or stderr).
-	logCommandOutput := func(logger *zap.Logger, reader io.ReadCloser) {
+	logCommandOutput := func(logger *slog.Logger, reader io.ReadCloser) {
 		r := bufio.NewReader(reader)
 		defer func(reader io.ReadCloser) {
 			err := reader.Close()
 			if err != nil && !strings.Contains(err.Error(), "file already closed") {
-				logger.Error(fmt.Sprintf("close reader: %s", err))
+				logger.ErrorContext(context.Background(), fmt.Sprintf("close reader: %s", err))
 			}
 		}(reader)
 
@@ -165,20 +163,20 @@ func (cmd *Cmd) pipeOutput() error {
 			line, _, err := r.ReadLine()
 			if err != nil {
 				if err != io.EOF && !strings.Contains(err.Error(), "file already closed") {
-					logger.Error(fmt.Sprintf("pipe unix process output error: %s", err))
+					logger.ErrorContext(context.Background(), fmt.Sprintf("pipe unix process output error: %s", err))
 				}
 
 				break
 			}
 
 			if len(line) != 0 {
-				logger.Debug(string(line))
+				logger.DebugContext(context.Background(), string(line))
 			}
 		}
 	}
 
-	go logCommandOutput(cmd.logger.Named("stdout"), stdout)
-	go logCommandOutput(cmd.logger.Named("stderr"), stderr)
+	go logCommandOutput(cmd.logger.With(slog.String("logger", "stdout")), stdout)
+	go logCommandOutput(cmd.logger.With(slog.String("logger", "stderr")), stderr)
 
 	return nil
 }
@@ -196,13 +194,13 @@ func (cmd *Cmd) Kill() error {
 
 	err := syscall.Kill(-cmd.process.Process.Pid, syscall.SIGKILL)
 	if err == nil {
-		cmd.logger.Debug("unix process killed")
+		cmd.logger.DebugContext(context.Background(), "unix process killed")
 		return nil
 	}
 
 	// If the process does not exist anymore, the error is irrelevant.
 	if strings.Contains(err.Error(), "no such process") {
-		cmd.logger.Debug("unix process already killed")
+		cmd.logger.DebugContext(context.Background(), "unix process already killed")
 		return nil
 	}
 

pkg/gotenberg/gc.go

@@ -1,19 +1,19 @@
 package gotenberg
 
 import (
+	"context"
 	"fmt"
+	"log/slog"
 	"os"
 	"path/filepath"
 	"strings"
 	"time"
-
-	"go.uber.org/zap"
 )
 
 // GarbageCollect scans the root path and deletes files or directories with
 // names containing specific substrings and before a given expiration time.
-func GarbageCollect(logger *zap.Logger, rootPath string, includeSubstr []string, expirationTime time.Time) error {
-	logger = logger.Named("gc")
+func GarbageCollect(ctx context.Context, logger *slog.Logger, rootPath string, includeSubstr []string, expirationTime time.Time) error {
+	logger = logger.With(slog.String("logger", "gc"))
 
 	// To make sure that the next Walk method stays on
 	// the root level of the considered path, we have to
@@ -38,12 +38,12 @@ func GarbageCollect(logger *zap.Logger, rootPath string, includeSubstr []string,
 
 		for _, substr := range includeSubstr {
 			if (strings.Contains(info.Name(), substr) || path == substr) && info.ModTime().Before(expirationTime) {
-				err := os.RemoveAll(path)
+				err := os.RemoveAll(path) //nolint:gosec // G122: rootPath is a trusted internal working directory
 				if err != nil {
 					return fmt.Errorf("garbage collect '%s': %w", path, err)
 				}
 
-				logger.Debug(fmt.Sprintf("'%s' removed", path))
+				logger.DebugContext(ctx, fmt.Sprintf("'%s' removed", path))
 
 				return skipDirOrNil(info)
 			}

pkg/gotenberg/gc_test.go

@@ -1,14 +1,15 @@
 package gotenberg
 
 import (
+	"context"
 	"fmt"
+	"log/slog"
 	"os"
 	"path"
 	"testing"
 	"time"
 
 	"github.com/google/uuid"
-	"go.uber.org/zap"
 )
 
 func TestGarbageCollect(t *testing.T) {
@@ -66,7 +67,7 @@ func TestGarbageCollect(t *testing.T) {
 				}
 			}()
 
-			err := GarbageCollect(zap.NewNop(), tc.rootPath, tc.includeSubstr, time.Now())
+			err := GarbageCollect(context.Background(), slog.New(slog.DiscardHandler), tc.rootPath, tc.includeSubstr, time.Now())
 
 			if !tc.expectError && err != nil {
 				t.Fatalf("expected no error but got: %v", err)

pkg/gotenberg/internal/log/color.go

@@ -1,9 +1,8 @@
-package logging
+package log
 
 import (
 	"fmt"
-
-	"go.uber.org/zap/zapcore"
+	"log/slog"
 )
 
 // Foreground colors.
@@ -25,23 +24,15 @@ func (c color) Add(s string) string {
 	return fmt.Sprintf("\x1b[%dm%s\x1b[0m", uint8(c), s)
 }
 
-func levelToColor(l zapcore.Level) color {
+func levelToColor(l slog.Level) color {
 	switch l {
-	case zapcore.DebugLevel:
+	case slog.LevelDebug:
 		return cyan
-	case zapcore.InfoLevel:
+	case slog.LevelInfo:
 		return blue
-	case zapcore.WarnLevel:
+	case slog.LevelWarn:
 		return yellow
-	case zapcore.ErrorLevel:
-		return red
-	case zapcore.DPanicLevel:
-		return red
-	case zapcore.PanicLevel:
-		return red
-	case zapcore.FatalLevel:
-		return red
-	case zapcore.InvalidLevel:
+	case slog.LevelError:
 		return red
 	default:
 		return red

pkg/gotenberg/internal/log/doc.go

@@ -0,0 +1,2 @@
+// Package log gathers internal logging utilities.
+package log

pkg/gotenberg/internal/log/gcp.go

@@ -0,0 +1,18 @@
+package log
+
+import "log/slog"
+
+func gcpSeverity(l slog.Level) string {
+	switch {
+	case l < slog.LevelInfo:
+		return "DEBUG"
+	case l < slog.LevelWarn:
+		return "INFO"
+	case l < slog.LevelError:
+		return "WARNING"
+	case l >= slog.LevelError:
+		return "ERROR"
+	default:
+		return "DEFAULT"
+	}
+}

pkg/gotenberg/internal/log/handler.go

@@ -0,0 +1,171 @@
+package log
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+)
+
+type gotenbergHandler struct {
+	slog.Handler
+	fieldsPrefix string
+	loggerName   string
+}
+
+func NewGotenbergHandler(next slog.Handler, prefix string) slog.Handler {
+	return &gotenbergHandler{Handler: next, fieldsPrefix: prefix}
+}
+
+func (h *gotenbergHandler) Handle(ctx context.Context, r slog.Record) error {
+	var newAttrs []slog.Attr
+
+	if h.loggerName != "" {
+		newAttrs = append(newAttrs, slog.String("logger", h.loggerName))
+	}
+
+	var needsNewRecord bool
+	if len(newAttrs) > 0 {
+		needsNewRecord = true
+	}
+
+	if h.fieldsPrefix != "" {
+		r.Attrs(func(a slog.Attr) bool {
+			if a.Key == "logger" || a.Key == "correlation_id" || a.Key == "trace_id" || a.Key == "span_id" {
+				newAttrs = append(newAttrs, a)
+				needsNewRecord = true
+				return true
+			}
+			a.Key = h.fieldsPrefix + "_" + a.Key
+			newAttrs = append(newAttrs, a)
+			needsNewRecord = true
+			return true
+		})
+	} else if needsNewRecord {
+		r.Attrs(func(a slog.Attr) bool {
+			newAttrs = append(newAttrs, a)
+			return true
+		})
+	}
+
+	if needsNewRecord {
+		newR := slog.NewRecord(r.Time, r.Level, r.Message, r.PC)
+		newR.AddAttrs(newAttrs...)
+		r = newR
+	}
+
+	return h.Handler.Handle(ctx, r)
+}
+
+func (h *gotenbergHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	var prefixed []slog.Attr
+	newLoggerName := h.loggerName
+
+	for _, a := range attrs {
+		if a.Key == "logger" {
+			if newLoggerName == "" {
+				newLoggerName = a.Value.String()
+			} else {
+				newLoggerName = newLoggerName + "." + a.Value.String()
+			}
+			continue
+		}
+
+		if h.fieldsPrefix != "" {
+			if a.Key == "correlation_id" || a.Key == "trace_id" || a.Key == "span_id" {
+				// Don't prefix these keys
+			} else {
+				a.Key = h.fieldsPrefix + "_" + a.Key
+			}
+		}
+		prefixed = append(prefixed, a)
+	}
+
+	newHandler := h.Handler
+	if len(prefixed) > 0 {
+		newHandler = h.Handler.WithAttrs(prefixed)
+	}
+
+	return &gotenbergHandler{
+		Handler:      newHandler,
+		fieldsPrefix: h.fieldsPrefix,
+		loggerName:   newLoggerName,
+	}
+}
+
+func (h *gotenbergHandler) WithGroup(name string) slog.Handler {
+	return &gotenbergHandler{
+		Handler:      h.Handler.WithGroup(name),
+		fieldsPrefix: h.fieldsPrefix,
+		loggerName:   h.loggerName,
+	}
+}
+
+type multiHandler struct {
+	handlers []slog.Handler
+}
+
+func FanOut(handlers ...slog.Handler) slog.Handler {
+	return &multiHandler{handlers: handlers}
+}
+
+func (m *multiHandler) Enabled(ctx context.Context, level slog.Level) bool {
+	for _, h := range m.handlers {
+		if h.Enabled(ctx, level) {
+			return true
+		}
+	}
+	return false
+}
+
+func (m *multiHandler) Handle(ctx context.Context, r slog.Record) error {
+	var errs []error
+	for _, h := range m.handlers {
+		if h.Enabled(ctx, r.Level) {
+			if err := h.Handle(ctx, r.Clone()); err != nil {
+				errs = append(errs, err)
+			}
+		}
+	}
+	return errors.Join(errs...)
+}
+
+func (m *multiHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	cloned := make([]slog.Handler, len(m.handlers))
+	for i, h := range m.handlers {
+		cloned[i] = h.WithAttrs(attrs)
+	}
+	return &multiHandler{handlers: cloned}
+}
+
+func (m *multiHandler) WithGroup(name string) slog.Handler {
+	cloned := make([]slog.Handler, len(m.handlers))
+	for i, h := range m.handlers {
+		cloned[i] = h.WithGroup(name)
+	}
+	return &multiHandler{handlers: cloned}
+}
+
+type levelHandler struct {
+	slog.Handler
+	level slog.Level
+}
+
+func LevelFilter(next slog.Handler, level slog.Level) slog.Handler {
+	return &levelHandler{Handler: next, level: level}
+}
+
+func (h *levelHandler) Enabled(ctx context.Context, level slog.Level) bool {
+	return level >= h.level && h.Handler.Enabled(ctx, level)
+}
+
+func (h *levelHandler) Handle(ctx context.Context, r slog.Record) error {
+	return h.Handler.Handle(ctx, r)
+}
+
+func (h *levelHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return &levelHandler{Handler: h.Handler.WithAttrs(attrs), level: h.level}
+}
+
+func (h *levelHandler) WithGroup(name string) slog.Handler {
+	return &levelHandler{Handler: h.Handler.WithGroup(name), level: h.level}
+}

pkg/gotenberg/internal/log/log.go

@@ -0,0 +1,37 @@
+package log
+
+import (
+	"log/slog"
+	"sync"
+)
+
+// InitLogger initializes the global logger.
+func InitLogger(handler slog.Handler) {
+	if logger != nil {
+		return
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+
+	// Double check: ensure it wasn't initialized while we waited for the lock.
+	if logger != nil {
+		return
+	}
+
+	logger = slog.New(handler)
+}
+
+// Logger returns the global logger.
+func Logger() *slog.Logger {
+	mu.Lock()
+	defer mu.Unlock()
+
+	return logger
+}
+
+// logger is Singleton so that we instantiate our [slog.Logger] only once.
+var (
+	logger *slog.Logger
+	mu     sync.Mutex
+)

pkg/gotenberg/internal/log/stdhandler.go

@@ -0,0 +1,128 @@
+package log
+
+import (
+	"context"
+	"log/slog"
+	"os"
+	"strings"
+
+	"go.opentelemetry.io/otel/trace"
+	"golang.org/x/term"
+)
+
+const (
+	autoLoggingFormat = "auto"
+	jsonLoggingFormat = "json"
+	textLoggingFormat = "text"
+)
+
+// traceContextHandler is an internal wrapper that specifically injects
+// trace_id and span_id into the log record before they are written to the standard output.
+type traceContextHandler struct {
+	slog.Handler
+}
+
+func (h traceContextHandler) Handle(ctx context.Context, r slog.Record) error {
+	if spanCtx := trace.SpanContextFromContext(ctx); spanCtx.IsValid() {
+		// Since slog.Record is immutable with regards to adding attributes in-place,
+		// we must clone and add them.
+		newR := slog.NewRecord(r.Time, r.Level, r.Message, r.PC)
+		r.Attrs(func(a slog.Attr) bool {
+			newR.AddAttrs(a)
+			return true
+		})
+		newR.AddAttrs(
+			slog.String("trace_id", spanCtx.TraceID().String()),
+			slog.String("span_id", spanCtx.SpanID().String()),
+		)
+		r = newR
+	}
+
+	return h.Handler.Handle(ctx, r)
+}
+
+func (h traceContextHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return traceContextHandler{Handler: h.Handler.WithAttrs(attrs)}
+}
+
+func (h traceContextHandler) WithGroup(name string) slog.Handler {
+	return traceContextHandler{Handler: h.Handler.WithGroup(name)}
+}
+
+// NewStdHandler returns a [slog.Handler] instance for the standard output.
+func NewStdHandler(level slog.Level, format string, fieldsPrefix string, enableGcpFields bool) (slog.Handler, error) {
+	// #nosec: G115
+	isTerminal := term.IsTerminal(int(os.Stdout.Fd()))
+
+	// Normalize the log format based on the output device.
+	if format == autoLoggingFormat {
+		if isTerminal {
+			format = textLoggingFormat
+		} else {
+			format = jsonLoggingFormat
+		}
+	}
+
+	opts := &slog.HandlerOptions{
+		Level: level,
+	}
+
+	opts.ReplaceAttr = func(groups []string, a slog.Attr) slog.Attr {
+		// Configure level encoding based on format and GCP settings.
+		if a.Key == slog.LevelKey {
+			l := a.Value.Any().(slog.Level)
+			switch {
+			case format == textLoggingFormat && isTerminal:
+				if enableGcpFields {
+					a.Value = slog.StringValue(gcpSeverityColorEncoder(l))
+				} else {
+					a.Value = slog.StringValue(levelToColor(l).Add(l.String()))
+				}
+			case enableGcpFields && format != textLoggingFormat:
+				a.Key = "severity"
+				a.Value = slog.StringValue(gcpSeverity(l))
+			default:
+				a.Value = slog.StringValue(strings.ToLower(l.String()))
+			}
+		}
+
+		if a.Key == slog.TimeKey {
+			if enableGcpFields && format != textLoggingFormat {
+				a.Key = "time"
+			} else {
+				a.Key = "ts"
+			}
+
+			if isTerminal {
+				a.Value = slog.StringValue(a.Value.Time().Local().Format("2006/01/02 15:04:05.000"))
+			} else if !enableGcpFields {
+				a.Value = slog.Float64Value(float64(a.Value.Time().UnixNano()) / 1e9)
+			}
+		}
+
+		if a.Key == slog.MessageKey {
+			if enableGcpFields && format != textLoggingFormat {
+				a.Key = "message"
+			} else {
+				a.Key = "msg"
+			}
+		}
+
+		return a
+	}
+
+	var handler slog.Handler
+	if format == textLoggingFormat {
+		handler = slog.NewTextHandler(os.Stderr, opts)
+	} else {
+		handler = slog.NewJSONHandler(os.Stderr, opts)
+	}
+
+	return traceContextHandler{Handler: handler}, nil
+}
+
+func gcpSeverityColorEncoder(l slog.Level) string {
+	severity := gcpSeverity(l)
+	c := levelToColor(l)
+	return c.Add(severity)
+}

pkg/gotenberg/internal/otel/doc.go

@@ -0,0 +1,8 @@
+// Package otel gathers initialization utilities for OpenTelemetry
+// instrumentation.
+//
+// This package has been significantly inspired by
+// https://github.com/lucavallin/gotel.
+//
+// See: https://opentelemetry.io/.
+package otel

pkg/gotenberg/internal/otel/otel.go

@@ -0,0 +1,166 @@
+package otel
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"os"
+	"sync/atomic"
+
+	"go.opentelemetry.io/contrib/bridges/otelslog"
+	"go.opentelemetry.io/contrib/exporters/autoexport"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/log/global"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/log"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/resource"
+	"go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.40.0"
+)
+
+// InitTracerProvider initializes the OpenTelemetry tracer provider.
+func InitTracerProvider(logger *slog.Logger, serviceName, serviceVersion string) (shutdown func(context.Context) error, err error) {
+	initOtelLogger(logger)
+
+	ctx := context.Background()
+	hostname, err := os.Hostname()
+	if err != nil {
+		return nil, fmt.Errorf("get hostname: %w", err)
+	}
+
+	res, err := resource.Merge(
+		resource.Default(),
+		resource.NewWithAttributes(
+			semconv.SchemaURL,
+			semconv.ServiceName(serviceName),
+			semconv.ServiceVersion(serviceVersion),
+			semconv.HostName(hostname),
+		),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("merge resource: %w", err)
+	}
+
+	traceOpts := []trace.TracerProviderOption{
+		trace.WithResource(res),
+	}
+
+	traceExporter, err := autoexport.NewSpanExporter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	if !autoexport.IsNoneSpanExporter(traceExporter) {
+		traceOpts = append(traceOpts, trace.WithBatcher(traceExporter))
+	}
+
+	traceProvider := trace.NewTracerProvider(traceOpts...)
+	otel.SetTracerProvider(traceProvider)
+
+	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	))
+
+	return traceProvider.Shutdown, nil
+}
+
+// InitMeterProvider initializes the OpenTelemetry meter provider.
+func InitMeterProvider(logger *slog.Logger, serviceName, serviceVersion string) (shutdown func(context.Context) error, err error) {
+	initOtelLogger(logger)
+
+	ctx := context.Background()
+	hostname, err := os.Hostname()
+	if err != nil {
+		return nil, fmt.Errorf("get hostname: %w", err)
+	}
+
+	res, err := resource.Merge(
+		resource.Default(),
+		resource.NewWithAttributes(
+			semconv.SchemaURL,
+			semconv.ServiceName(serviceName),
+			semconv.ServiceVersion(serviceVersion),
+			semconv.HostName(hostname),
+		),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("merge resource: %w", err)
+	}
+
+	metricOpts := []metric.Option{
+		metric.WithResource(res),
+	}
+
+	metricReader, err := autoexport.NewMetricReader(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	if !autoexport.IsNoneMetricReader(metricReader) {
+		metricOpts = append(metricOpts, metric.WithReader(metricReader))
+	}
+
+	meterProvider := metric.NewMeterProvider(metricOpts...)
+	otel.SetMeterProvider(meterProvider)
+
+	return meterProvider.Shutdown, nil
+}
+
+// InitLoggerProvider initializes the OpenTelemetry logger provider.
+func InitLoggerProvider(logger *slog.Logger, serviceName, serviceVersion string) (shutdown func(context.Context) error, handler slog.Handler, err error) {
+	initOtelLogger(logger)
+
+	ctx := context.Background()
+	hostname, err := os.Hostname()
+	if err != nil {
+		return nil, nil, fmt.Errorf("get hostname: %w", err)
+	}
+
+	res, err := resource.Merge(
+		resource.Default(),
+		resource.NewWithAttributes(
+			semconv.SchemaURL,
+			semconv.ServiceName(serviceName),
+			semconv.ServiceVersion(serviceVersion),
+			semconv.HostName(hostname),
+		),
+	)
+	if err != nil {
+		return nil, nil, fmt.Errorf("merge resource: %w", err)
+	}
+
+	logOpts := []log.LoggerProviderOption{
+		log.WithResource(res),
+	}
+
+	logExporter, err := autoexport.NewLogExporter(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if !autoexport.IsNoneLogExporter(logExporter) {
+		logOpts = append(logOpts, log.WithProcessor(log.NewBatchProcessor(logExporter)))
+	}
+
+	loggerProvider := log.NewLoggerProvider(logOpts...)
+	otelHandler := otelslog.NewHandler(serviceName, otelslog.WithLoggerProvider(loggerProvider))
+	global.SetLoggerProvider(loggerProvider)
+
+	return loggerProvider.Shutdown, otelHandler, nil
+}
+
+func initOtelLogger(logger *slog.Logger) {
+	if otlpLoggerInitialized.Load() {
+		return
+	}
+
+	otel.SetErrorHandler(otel.ErrorHandlerFunc(func(err error) {
+		logger.Error(err.Error())
+	}))
+
+	otlpLoggerInitialized.Store(true)
+}
+
+var otlpLoggerInitialized atomic.Bool

pkg/gotenberg/logging.go

@@ -1,57 +1 @@
 package gotenberg
-
-import (
-	"fmt"
-
-	"github.com/hashicorp/go-retryablehttp"
-	"go.uber.org/zap"
-)
-
-// LoggerProvider is an interface for a module that supplies a method for
-// creating a [zap.Logger] instance for use by other modules.
-//
-//	func (m *YourModule) Provision(ctx *gotenberg.Context) error {
-//		provider, _ := ctx.Module(new(gotenberg.LoggerProvider))
-//		logger, _   := provider.(gotenberg.LoggerProvider).Logger(m)
-//	}
-type LoggerProvider interface {
-	Logger(mod Module) (*zap.Logger, error)
-}
-
-// LeveledLogger is a wrapper around a [zap.Logger] so that it may be used by a
-// [retryablehttp.Client].
-type LeveledLogger struct {
-	logger *zap.Logger
-}
-
-// NewLeveledLogger instantiates a [LeveledLogger].
-func NewLeveledLogger(logger *zap.Logger) *LeveledLogger {
-	return &LeveledLogger{
-		logger: logger,
-	}
-}
-
-// Error logs a message at the error level using the wrapped zap.Logger.
-func (leveled LeveledLogger) Error(msg string, keysAndValues ...any) {
-	leveled.logger.Error(fmt.Sprintf("%s: %+v", msg, keysAndValues))
-}
-
-// Warn logs a message at the warning level using the wrapped zap.Logger.
-func (leveled LeveledLogger) Warn(msg string, keysAndValues ...any) {
-	leveled.logger.Warn(fmt.Sprintf("%s: %+v", msg, keysAndValues))
-}
-
-// Info logs a message at the info level using the wrapped zap.Logger.
-func (leveled LeveledLogger) Info(msg string, keysAndValues ...any) {
-	leveled.logger.Info(fmt.Sprintf("%s: %+v", msg, keysAndValues))
-}
-
-// Debug logs a message at the debug level using the wrapped zap.Logger.
-func (leveled LeveledLogger) Debug(msg string, keysAndValues ...any) {
-	leveled.logger.Debug(fmt.Sprintf("%s: %+v", msg, keysAndValues))
-}
-
-// Interface guards.
-var (
-	_ retryablehttp.LeveledLogger = (*LeveledLogger)(nil)
-)

pkg/gotenberg/mocks.go

@@ -2,9 +2,8 @@ package gotenberg
 
 import (
 	"context"
+	"log/slog"
 	"os"
-
-	"go.uber.org/zap"
 )
 
 // ModuleMock is a mock for the [Module] interface.
@@ -46,75 +45,75 @@ func (mod *DebuggableMock) Debug() map[string]any {
 //
 //nolint:dupl
 type PdfEngineMock struct {
-	MergeMock          func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error
-	SplitMock          func(ctx context.Context, logger *zap.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error)
-	FlattenMock        func(ctx context.Context, logger *zap.Logger, inputPath string) error
-	ConvertMock        func(ctx context.Context, logger *zap.Logger, formats PdfFormats, inputPath, outputPath string) error
-	ReadMetadataMock   func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error)
-	PageCountMock      func(ctx context.Context, logger *zap.Logger, inputPath string) (int, error)
-	WriteMetadataMock  func(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error
-	ReadBookmarksMock  func(ctx context.Context, logger *zap.Logger, inputPath string) ([]Bookmark, error)
-	EncryptMock        func(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error
-	EmbedFilesMock     func(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error
-	WriteBookmarksMock func(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []Bookmark) error
-	WatermarkMock      func(ctx context.Context, logger *zap.Logger, inputPath string, stamp Stamp) error
-	StampMock          func(ctx context.Context, logger *zap.Logger, inputPath string, stamp Stamp) error
-	RotateMock         func(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error
+	MergeMock          func(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error
+	SplitMock          func(ctx context.Context, logger *slog.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error)
+	FlattenMock        func(ctx context.Context, logger *slog.Logger, inputPath string) error
+	ConvertMock        func(ctx context.Context, logger *slog.Logger, formats PdfFormats, inputPath, outputPath string) error
+	ReadMetadataMock   func(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error)
+	PageCountMock      func(ctx context.Context, logger *slog.Logger, inputPath string) (int, error)
+	WriteMetadataMock  func(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error
+	ReadBookmarksMock  func(ctx context.Context, logger *slog.Logger, inputPath string) ([]Bookmark, error)
+	EncryptMock        func(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error
+	EmbedFilesMock     func(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error
+	WriteBookmarksMock func(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []Bookmark) error
+	WatermarkMock      func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
+	StampMock          func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
+	RotateMock         func(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error
 }
 
-func (engine *PdfEngineMock) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+func (engine *PdfEngineMock) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
 	return engine.MergeMock(ctx, logger, inputPaths, outputPath)
 }
 
-func (engine *PdfEngineMock) Split(ctx context.Context, logger *zap.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error) {
+func (engine *PdfEngineMock) Split(ctx context.Context, logger *slog.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error) {
 	return engine.SplitMock(ctx, logger, mode, inputPath, outputDirPath)
 }
 
-func (engine *PdfEngineMock) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
+func (engine *PdfEngineMock) Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error {
 	return engine.FlattenMock(ctx, logger, inputPath)
 }
 
-func (engine *PdfEngineMock) Convert(ctx context.Context, logger *zap.Logger, formats PdfFormats, inputPath, outputPath string) error {
+func (engine *PdfEngineMock) Convert(ctx context.Context, logger *slog.Logger, formats PdfFormats, inputPath, outputPath string) error {
 	return engine.ConvertMock(ctx, logger, formats, inputPath, outputPath)
 }
 
-func (engine *PdfEngineMock) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error) {
+func (engine *PdfEngineMock) ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error) {
 	return engine.ReadMetadataMock(ctx, logger, inputPath)
 }
 
-func (engine *PdfEngineMock) PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error) {
+func (engine *PdfEngineMock) PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error) {
 	return engine.PageCountMock(ctx, logger, inputPath)
 }
 
-func (engine *PdfEngineMock) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error {
+func (engine *PdfEngineMock) WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error {
 	return engine.WriteMetadataMock(ctx, logger, metadata, inputPath)
 }
 
-func (engine *PdfEngineMock) ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]Bookmark, error) {
+func (engine *PdfEngineMock) ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]Bookmark, error) {
 	return engine.ReadBookmarksMock(ctx, logger, inputPath)
 }
 
-func (engine *PdfEngineMock) Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error {
+func (engine *PdfEngineMock) Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error {
 	return engine.EncryptMock(ctx, logger, inputPath, userPassword, ownerPassword)
 }
 
-func (engine *PdfEngineMock) EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error {
+func (engine *PdfEngineMock) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {
 	return engine.EmbedFilesMock(ctx, logger, filePaths, inputPath)
 }
 
-func (engine *PdfEngineMock) WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []Bookmark) error {
+func (engine *PdfEngineMock) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []Bookmark) error {
 	return engine.WriteBookmarksMock(ctx, logger, inputPath, bookmarks)
 }
 
-func (engine *PdfEngineMock) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp Stamp) error {
+func (engine *PdfEngineMock) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error {
 	return engine.WatermarkMock(ctx, logger, inputPath, stamp)
 }
 
-func (engine *PdfEngineMock) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp Stamp) error {
+func (engine *PdfEngineMock) Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error {
 	return engine.StampMock(ctx, logger, inputPath, stamp)
 }
 
-func (engine *PdfEngineMock) Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error {
+func (engine *PdfEngineMock) Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error {
 	return engine.RotateMock(ctx, logger, inputPath, angle, pages)
 }
 
@@ -129,31 +128,32 @@ func (provider *PdfEngineProviderMock) PdfEngine() (PdfEngine, error) {
 
 // ProcessMock is a mock for the [Process] interface.
 type ProcessMock struct {
-	StartMock   func(logger *zap.Logger) error
-	StopMock    func(logger *zap.Logger) error
-	HealthyMock func(logger *zap.Logger) bool
+	StartMock   func(logger *slog.Logger) error
+	StopMock    func(logger *slog.Logger) error
+	HealthyMock func(logger *slog.Logger) bool
 }
 
-func (p *ProcessMock) Start(logger *zap.Logger) error {
+func (p *ProcessMock) Start(logger *slog.Logger) error {
 	return p.StartMock(logger)
 }
 
-func (p *ProcessMock) Stop(logger *zap.Logger) error {
+func (p *ProcessMock) Stop(logger *slog.Logger) error {
 	return p.StopMock(logger)
 }
 
-func (p *ProcessMock) Healthy(logger *zap.Logger) bool {
+func (p *ProcessMock) Healthy(logger *slog.Logger) bool {
 	return p.HealthyMock(logger)
 }
 
 // ProcessSupervisorMock is a mock for the [ProcessSupervisor] interface.
 type ProcessSupervisorMock struct {
-	LaunchMock        func() error
-	ShutdownMock      func() error
-	HealthyMock       func() bool
-	RunMock           func(ctx context.Context, logger *zap.Logger, task func() error) error
-	ReqQueueSizeMock  func() int64
-	RestartsCountMock func() int64
+	LaunchMock           func() error
+	ShutdownMock         func() error
+	HealthyMock          func() bool
+	RunMock              func(ctx context.Context, logger *slog.Logger, task func() error) error
+	ReqQueueSizeMock     func() int64
+	RestartsCountMock    func() int64
+	ActiveTasksCountMock func() int64
 }
 
 func (s *ProcessSupervisorMock) Launch() error {
@@ -168,7 +168,7 @@ func (s *ProcessSupervisorMock) Healthy() bool {
 	return s.HealthyMock()
 }
 
-func (s *ProcessSupervisorMock) Run(ctx context.Context, logger *zap.Logger, task func() error) error {
+func (s *ProcessSupervisorMock) Run(ctx context.Context, logger *slog.Logger, task func() error) error {
 	return s.RunMock(ctx, logger, task)
 }
 
@@ -180,13 +180,8 @@ func (s *ProcessSupervisorMock) RestartsCount() int64 {
 	return s.RestartsCountMock()
 }
 
-// LoggerProviderMock is a mock for the [LoggerProvider] interface.
-type LoggerProviderMock struct {
-	LoggerMock func(mod Module) (*zap.Logger, error)
-}
-
-func (provider *LoggerProviderMock) Logger(mod Module) (*zap.Logger, error) {
-	return provider.LoggerMock(mod)
+func (s *ProcessSupervisorMock) ActiveTasksCount() int64 {
+	return s.ActiveTasksCountMock()
 }
 
 // MetricsProviderMock is a mock for the [MetricsProvider] interface.
@@ -224,7 +219,6 @@ var (
 	_ PdfEngineProvider = (*PdfEngineProviderMock)(nil)
 	_ Process           = (*ProcessMock)(nil)
 	_ ProcessSupervisor = (*ProcessSupervisorMock)(nil)
-	_ LoggerProvider    = (*LoggerProviderMock)(nil)
 	_ MetricsProvider   = (*MetricsProviderMock)(nil)
 	_ MkdirAll          = (*MkdirAllMock)(nil)
 	_ PathRename        = (*PathRenameMock)(nil)

pkg/gotenberg/pdfengine.go

@@ -4,8 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
-
-	"go.uber.org/zap"
+	"log/slog"
 )
 
 var (
@@ -160,57 +159,57 @@ type Bookmark struct {
 type PdfEngine interface {
 	// Merge combines multiple PDFs into a single PDF. The resulting page order
 	// is determined by the order of files provided in inputPaths.
-	Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error
+	Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error
 
 	// Split splits a given PDF file.
-	Split(ctx context.Context, logger *zap.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error)
+	Split(ctx context.Context, logger *slog.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error)
 
 	// Flatten merges existing annotation appearances with page content,
 	// effectively deleting the original annotations. This process can flatten
 	// forms as well as forms share a relationship with annotations. Note that
 	// this operation is irreversible.
-	Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error
+	Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error
 
 	// Convert transforms a given PDF to the specified formats defined in
 	// PdfFormats. If no format, it does nothing.
-	Convert(ctx context.Context, logger *zap.Logger, formats PdfFormats, inputPath, outputPath string) error
+	Convert(ctx context.Context, logger *slog.Logger, formats PdfFormats, inputPath, outputPath string) error
 
 	// ReadMetadata extracts the metadata of a given PDF file.
-	ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error)
+	ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error)
 
 	// PageCount returns the number of pages in a PDF file.
-	PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error)
+	PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error)
 
 	// WriteMetadata writes the metadata into a given PDF file.
-	WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error
+	WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error
 
 	// ReadBookmarks reads the document outline (bookmarks) of a PDF file.
-	ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]Bookmark, error)
+	ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]Bookmark, error)
 
 	// WriteBookmarks adds a document outline (bookmarks) to a PDF file.
 	// The bookmarks parameter represents the hierarchical tree of the outline.
-	WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []Bookmark) error
+	WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []Bookmark) error
 
 	// Encrypt adds password protection to a PDF file.
 	// The userPassword is required to open the document.
 	// The ownerPassword provides full access to the document.
 	// If the ownerPassword is empty, it defaults to the userPassword.
-	Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error
+	Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error
 
 	// EmbedFiles embeds files into a PDF. All files are embedded as file attachments
 	// without modifying the main PDF content.
 	// TODO: attachments instead? Rename the route?
-	EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error
+	EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error
 
 	// Watermark applies a watermark (behind page content) to a PDF file.
-	Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp Stamp) error
+	Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
 
 	// Stamp applies a stamp (on top of page content) to a PDF file.
-	Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp Stamp) error
+	Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
 
 	// Rotate rotates pages of a PDF file by the given angle (90, 180, 270).
 	// If pages is empty, all pages are rotated.
-	Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error
+	Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error
 }
 
 // PdfEngineProvider offers an interface to instantiate a [PdfEngine].

pkg/gotenberg/semconv/bench_test.go

@@ -0,0 +1,48 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/bench_test.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv
+
+import (
+	"net/http"
+	"net/url"
+	"testing"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+var benchHTTPServerRequestResults []attribute.KeyValue
+
+// BenchmarkHTTPServerRequest allows comparison between different version of the HTTP server.
+// To use an alternative start this test with OTEL_SEMCONV_STABILITY_OPT_IN set to the
+// version under test.
+func BenchmarkHTTPServerRequest(b *testing.B) {
+	// Request was generated from TestHTTPServerRequest request.
+	req := &http.Request{
+		Method: http.MethodGet,
+		URL: &url.URL{
+			Path: "/",
+		},
+		Proto:      "HTTP/1.1",
+		ProtoMajor: 1,
+		ProtoMinor: 1,
+		Header: http.Header{
+			"User-Agent":      []string{"Go-http-client/1.1"},
+			"Accept-Encoding": []string{"gzip"},
+		},
+		Body:       http.NoBody,
+		Host:       "127.0.0.1:39093",
+		RemoteAddr: "127.0.0.1:38738",
+		RequestURI: "/",
+	}
+	serv := NewHTTPServer(nil)
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for range b.N {
+		benchHTTPServerRequestResults = serv.RequestTraceAttrs("", req, RequestTraceAttrsOpts{})
+	}
+}

pkg/gotenberg/semconv/client.go

@@ -0,0 +1,308 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/client.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package semconv provides OpenTelemetry semantic convention types and
+// functionality.
+package semconv // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp/internal/semconv"
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"reflect"
+	"slices"
+	"strconv"
+	"strings"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/semconv/v1.39.0"
+	"go.opentelemetry.io/otel/semconv/v1.39.0/httpconv"
+)
+
+type HTTPClient struct {
+	requestBodySize httpconv.ClientRequestBodySize
+	requestDuration httpconv.ClientRequestDuration
+}
+
+func NewHTTPClient(meter metric.Meter) HTTPClient {
+	client := HTTPClient{}
+
+	var err error
+	client.requestBodySize, err = httpconv.NewClientRequestBodySize(meter)
+	handleErr(err)
+
+	client.requestDuration, err = httpconv.NewClientRequestDuration(
+		meter,
+		metric.WithExplicitBucketBoundaries(0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10),
+	)
+	handleErr(err)
+
+	return client
+}
+
+func (n HTTPClient) Status(code int) (codes.Code, string) {
+	if code == 0 {
+		return codes.Error, "No HTTP status code"
+	}
+	if code < 100 || code >= 600 {
+		return codes.Error, fmt.Sprintf("Invalid HTTP status code %d", code)
+	}
+	if code >= 400 {
+		return codes.Error, http.StatusText(code)
+	}
+	return codes.Ok,  ""
+}
+
+// RequestTraceAttrs returns trace attributes for an HTTP request made by a client.
+func (n HTTPClient) RequestTraceAttrs(req *http.Request) []attribute.KeyValue {
+	/*
+	 below attributes are returned:
+	 - http.request.method
+	 - http.request.method.original
+	 - url.full
+	 - server.address
+	 - server.port
+	 - network.protocol.name
+	 - network.protocol.version
+	*/
+	numOfAttributes := 3 // URL, server address, proto, and method.
+
+	var urlHost string
+	if req.URL != nil {
+		urlHost = req.URL.Host
+	}
+	var requestHost string
+	var requestPort int
+	for _, hostport := range []string{urlHost, req.Header.Get("Host")} {
+		requestHost, requestPort = SplitHostPort(hostport)
+		if requestHost != "" || requestPort > 0 {
+			break
+		}
+	}
+
+	eligiblePort := requiredHTTPPort(req.URL != nil && req.URL.Scheme == "https", requestPort)
+	if eligiblePort > 0 {
+		numOfAttributes++
+	}
+	useragent := req.UserAgent()
+	if useragent != "" {
+		numOfAttributes++
+	}
+
+	protoName, protoVersion := netProtocol(req.Proto)
+	if protoName != "" && protoName != "http" {
+		numOfAttributes++
+	}
+	if protoVersion != "" {
+		numOfAttributes++
+	}
+
+	method, originalMethod := n.method(req.Method)
+	if originalMethod != (attribute.KeyValue{}) {
+		numOfAttributes++
+	}
+
+	attrs := make([]attribute.KeyValue, 0, numOfAttributes)
+
+	attrs = append(attrs, method)
+	if originalMethod != (attribute.KeyValue{}) {
+		attrs = append(attrs, originalMethod)
+	}
+
+	var u string
+	if req.URL != nil {
+		// Remove any username/password info that may be in the URL.
+		userinfo := req.URL.User
+		req.URL.User = nil
+		u = req.URL.String()
+		// Restore any username/password info that was removed.
+		req.URL.User = userinfo
+	}
+	attrs = append(attrs, semconv.URLFull(u))
+
+	attrs = append(attrs, semconv.ServerAddress(requestHost))
+	if eligiblePort > 0 {
+		attrs = append(attrs, semconv.ServerPort(eligiblePort))
+	}
+
+	if protoName != "" && protoName != "http" {
+		attrs = append(attrs, semconv.NetworkProtocolName(protoName))
+	}
+	if protoVersion != "" {
+		attrs = append(attrs, semconv.NetworkProtocolVersion(protoVersion))
+	}
+
+	return attrs
+}
+
+// ResponseTraceAttrs returns trace attributes for an HTTP response made by a client.
+func (n HTTPClient) ResponseTraceAttrs(resp *http.Response) []attribute.KeyValue {
+	/*
+	 below attributes are returned:
+	 - http.response.status_code
+	 - error.type
+	*/
+	var count int
+	if resp.StatusCode > 0 {
+		count++
+	}
+
+	if isErrorStatusCode(resp.StatusCode) {
+		count++
+	}
+
+	attrs := make([]attribute.KeyValue, 0, count)
+	if resp.StatusCode > 0 {
+		attrs = append(attrs, semconv.HTTPResponseStatusCode(resp.StatusCode))
+	}
+
+	if isErrorStatusCode(resp.StatusCode) {
+		errorType := strconv.Itoa(resp.StatusCode)
+		attrs = append(attrs, semconv.ErrorTypeKey.String(errorType))
+	}
+	return attrs
+}
+
+func (n HTTPClient) ErrorType(err error) attribute.KeyValue {
+	t := reflect.TypeOf(err)
+	var value string
+	if t.PkgPath() == "" && t.Name() == "" {
+		// Likely a builtin type.
+		value = t.String()
+	} else {
+		value = fmt.Sprintf("%s.%s", t.PkgPath(), t.Name())
+	}
+
+	if value == "" {
+		return semconv.ErrorTypeOther
+	}
+
+	return semconv.ErrorTypeKey.String(value)
+}
+
+func (n HTTPClient) method(method string) (attribute.KeyValue, attribute.KeyValue) {
+	if method == "" {
+		return semconv.HTTPRequestMethodGet, attribute.KeyValue{}
+	}
+	if attr, ok := methodLookup[method]; ok {
+		return attr, attribute.KeyValue{}
+	}
+
+	orig := semconv.HTTPRequestMethodOriginal(method)
+	if attr, ok := methodLookup[strings.ToUpper(method)]; ok {
+		return attr, orig
+	}
+	return semconv.HTTPRequestMethodGet, orig
+}
+
+func (n HTTPClient) MetricAttributes(req *http.Request, statusCode int, additionalAttributes []attribute.KeyValue) []attribute.KeyValue {
+	num := len(additionalAttributes) + 2
+	var h string
+	if req.URL != nil {
+		h = req.URL.Host
+	}
+	var requestHost string
+	var requestPort int
+	for _, hostport := range []string{h, req.Header.Get("Host")} {
+		requestHost, requestPort = SplitHostPort(hostport)
+		if requestHost != "" || requestPort > 0 {
+			break
+		}
+	}
+
+	port := requiredHTTPPort(req.URL != nil && req.URL.Scheme == "https", requestPort)
+	if port > 0 {
+		num++
+	}
+
+	protoName, protoVersion := netProtocol(req.Proto)
+	if protoName != "" {
+		num++
+	}
+	if protoVersion != "" {
+		num++
+	}
+
+	if statusCode > 0 {
+		num++
+	}
+
+	attributes := slices.Grow(additionalAttributes, num)
+	attributes = append(attributes,
+		semconv.HTTPRequestMethodKey.String(standardizeHTTPMethod(req.Method)),
+		semconv.ServerAddress(requestHost),
+		n.scheme(req),
+	)
+
+	if port > 0 {
+		attributes = append(attributes, semconv.ServerPort(port))
+	}
+	if protoName != "" {
+		attributes = append(attributes, semconv.NetworkProtocolName(protoName))
+	}
+	if protoVersion != "" {
+		attributes = append(attributes, semconv.NetworkProtocolVersion(protoVersion))
+	}
+
+	if statusCode > 0 {
+		attributes = append(attributes, semconv.HTTPResponseStatusCode(statusCode))
+	}
+	return attributes
+}
+
+type MetricOpts struct {
+	measurement metric.MeasurementOption
+	addOptions  metric.AddOption
+}
+
+func (o MetricOpts) MeasurementOption() metric.MeasurementOption {
+	return o.measurement
+}
+
+func (o MetricOpts) AddOptions() metric.AddOption {
+	return o.addOptions
+}
+
+func (n HTTPClient) MetricOptions(ma MetricAttributes) map[string]MetricOpts {
+	opts := map[string]MetricOpts{}
+
+	attributes := n.MetricAttributes(ma.Req, ma.StatusCode, ma.AdditionalAttributes)
+	set := metric.WithAttributeSet(attribute.NewSet(attributes...))
+	opts["new"] = MetricOpts{
+		measurement: set,
+		addOptions:  set,
+	}
+
+	return opts
+}
+
+func (n HTTPClient) RecordMetrics(ctx context.Context, md MetricData, opts map[string]MetricOpts) {
+	n.requestBodySize.Inst().Record(ctx, md.RequestSize, opts["new"].MeasurementOption())
+	n.requestDuration.Inst().Record(ctx, md.ElapsedTime/1000, opts["new"].MeasurementOption())
+}
+
+// TraceAttributes returns attributes for httptrace.
+func (n HTTPClient) TraceAttributes(host string) []attribute.KeyValue {
+	return []attribute.KeyValue{
+		semconv.ServerAddress(host),
+	}
+}
+
+func (n HTTPClient) scheme(req *http.Request) attribute.KeyValue {
+	if req.URL != nil && req.URL.Scheme != "" {
+		return semconv.URLScheme(req.URL.Scheme)
+	}
+	if req.TLS != nil {
+		return semconv.URLScheme("https")
+	}
+	return semconv.URLScheme("http")
+}
+
+func isErrorStatusCode(code int) bool {
+	return code >= 400 || code < 100
+}

pkg/gotenberg/semconv/client_test.go

@@ -0,0 +1,182 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/client_test.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv
+
+import (
+	"net/http"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+)
+
+func TestHTTPClientStatus(t *testing.T) {
+	tests := []struct {
+		code int
+		stat codes.Code
+		msg  bool
+	}{
+		{0, codes.Error, true},
+		{http.StatusContinue, codes.Ok, false},
+		{http.StatusSwitchingProtocols, codes.Ok, false},
+		{http.StatusProcessing, codes.Ok, false},
+		{http.StatusEarlyHints, codes.Ok, false},
+		{http.StatusOK, codes.Ok, false},
+		{http.StatusCreated, codes.Ok, false},
+		{http.StatusAccepted, codes.Ok, false},
+		{http.StatusNonAuthoritativeInfo, codes.Ok, false},
+		{http.StatusNoContent, codes.Ok, false},
+		{http.StatusResetContent, codes.Ok, false},
+		{http.StatusPartialContent, codes.Ok, false},
+		{http.StatusMultiStatus, codes.Ok, false},
+		{http.StatusAlreadyReported, codes.Ok, false},
+		{http.StatusIMUsed, codes.Ok, false},
+		{http.StatusMultipleChoices, codes.Ok, false},
+		{http.StatusMovedPermanently, codes.Ok, false},
+		{http.StatusFound, codes.Ok, false},
+		{http.StatusSeeOther, codes.Ok, false},
+		{http.StatusNotModified, codes.Ok, false},
+		{http.StatusUseProxy, codes.Ok, false},
+		{306, codes.Ok, false},
+		{http.StatusTemporaryRedirect, codes.Ok, false},
+		{http.StatusPermanentRedirect, codes.Ok, false},
+		{http.StatusBadRequest, codes.Error, true},
+		{http.StatusUnauthorized, codes.Error, true},
+		{http.StatusPaymentRequired, codes.Error, true},
+		{http.StatusForbidden, codes.Error, true},
+		{http.StatusNotFound, codes.Error, true},
+		{http.StatusMethodNotAllowed, codes.Error, true},
+		{http.StatusNotAcceptable, codes.Error, true},
+		{http.StatusProxyAuthRequired, codes.Error, true},
+		{http.StatusRequestTimeout, codes.Error, true},
+		{http.StatusConflict, codes.Error, true},
+		{http.StatusGone, codes.Error, true},
+		{http.StatusLengthRequired, codes.Error, true},
+		{http.StatusPreconditionFailed, codes.Error, true},
+		{http.StatusRequestEntityTooLarge, codes.Error, true},
+		{http.StatusRequestURITooLong, codes.Error, true},
+		{http.StatusUnsupportedMediaType, codes.Error, true},
+		{http.StatusRequestedRangeNotSatisfiable, codes.Error, true},
+		{http.StatusExpectationFailed, codes.Error, true},
+		{http.StatusTeapot, codes.Error, true},
+		{http.StatusMisdirectedRequest, codes.Error, true},
+		{http.StatusUnprocessableEntity, codes.Error, true},
+		{http.StatusLocked, codes.Error, true},
+		{http.StatusFailedDependency, codes.Error, true},
+		{http.StatusTooEarly, codes.Error, true},
+		{http.StatusUpgradeRequired, codes.Error, true},
+		{http.StatusPreconditionRequired, codes.Error, true},
+		{http.StatusTooManyRequests, codes.Error, true},
+		{http.StatusRequestHeaderFieldsTooLarge, codes.Error, true},
+		{http.StatusUnavailableForLegalReasons, codes.Error, true},
+		{499, codes.Error, false},
+		{http.StatusInternalServerError, codes.Error, true},
+		{http.StatusNotImplemented, codes.Error, true},
+		{http.StatusBadGateway, codes.Error, true},
+		{http.StatusServiceUnavailable, codes.Error, true},
+		{http.StatusGatewayTimeout, codes.Error, true},
+		{http.StatusHTTPVersionNotSupported, codes.Error, true},
+		{http.StatusVariantAlsoNegotiates, codes.Error, true},
+		{http.StatusInsufficientStorage, codes.Error, true},
+		{http.StatusLoopDetected, codes.Error, true},
+		{http.StatusNotExtended, codes.Error, true},
+		{http.StatusNetworkAuthenticationRequired, codes.Error, true},
+		{600, codes.Error, true},
+	}
+
+	for _, test := range tests {
+		t.Run(strconv.Itoa(test.code), func(t *testing.T) {
+			c, msg := HTTPClient{}.Status(test.code)
+			assert.Equal(t, test.stat, c)
+			if test.msg && msg == "" {
+				t.Errorf("expected non-empty message for %d", test.code)
+			} else if !test.msg && msg != "" {
+				t.Errorf("expected empty message for %d, got: %s", test.code, msg)
+			}
+		})
+	}
+}
+
+func TestHTTPClient_MetricAttributes(t *testing.T) {
+	defaultRequest, err := http.NewRequest("GET", "http://example.com/path?query=test", http.NoBody)
+	require.NoError(t, err)
+	httpsRequest, err := http.NewRequest("GET", "https://example.com/path?query=test", http.NoBody)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name                 string
+		server               string
+		req                  *http.Request
+		statusCode           int
+		additionalAttributes []attribute.KeyValue
+		wantFunc             func(t *testing.T, attrs []attribute.KeyValue)
+	}{
+		{
+			name:                 "routine testing",
+			req:                  defaultRequest,
+			statusCode:           200,
+			additionalAttributes: []attribute.KeyValue{attribute.String("test", "test")},
+			wantFunc: func(t *testing.T, attrs []attribute.KeyValue) {
+				require.Len(t, attrs, 7)
+				assert.ElementsMatch(t, []attribute.KeyValue{
+					attribute.String("http.request.method", "GET"),
+					attribute.String("server.address", "example.com"),
+					attribute.String("url.scheme", "http"),
+					attribute.String("network.protocol.name", "http"),
+					attribute.String("network.protocol.version", "1.1"),
+					attribute.Int64("http.response.status_code", 200),
+					attribute.String("test", "test"),
+				}, attrs)
+			},
+		},
+		{
+			name:                 "use server address",
+			req:                  defaultRequest,
+			statusCode:           200,
+			additionalAttributes: nil,
+			wantFunc: func(t *testing.T, attrs []attribute.KeyValue) {
+				require.Len(t, attrs, 6)
+				assert.ElementsMatch(t, []attribute.KeyValue{
+					attribute.String("http.request.method", "GET"),
+					attribute.String("server.address", "example.com"),
+					attribute.String("url.scheme", "http"),
+					attribute.String("network.protocol.name", "http"),
+					attribute.String("network.protocol.version", "1.1"),
+					attribute.Int64("http.response.status_code", 200),
+				}, attrs)
+			},
+		},
+		{
+			name:                 "https scheme",
+			req:                  httpsRequest,
+			statusCode:           200,
+			additionalAttributes: nil,
+			wantFunc: func(t *testing.T, attrs []attribute.KeyValue) {
+				require.Len(t, attrs, 6)
+				assert.ElementsMatch(t, []attribute.KeyValue{
+					attribute.String("http.request.method", "GET"),
+					attribute.String("server.address", "example.com"),
+					attribute.String("url.scheme", "https"),
+					attribute.String("network.protocol.name", "http"),
+					attribute.String("network.protocol.version", "1.1"),
+					attribute.Int64("http.response.status_code", 200),
+				}, attrs)
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := HTTPClient{}.MetricAttributes(tt.req, tt.statusCode, tt.additionalAttributes)
+			tt.wantFunc(t, got)
+		})
+	}
+}

pkg/gotenberg/semconv/common_test.go

@@ -0,0 +1,71 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/common_test.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg/semconv"
+	"go.opentelemetry.io/otel/attribute"
+)
+
+type testServerReq struct {
+	hostname   string
+	serverPort int
+	peerAddr   string
+	peerPort   int
+	clientIP   string
+}
+
+func testTraceRequest(t *testing.T, serv semconv.HTTPServer, want func(testServerReq) []attribute.KeyValue) {
+	t.Helper()
+
+	got := make(chan *http.Request, 1)
+	handler := func(w http.ResponseWriter, r *http.Request) {
+		got <- r
+		close(got)
+		w.WriteHeader(http.StatusOK)
+	}
+
+	srv := httptest.NewServer(http.HandlerFunc(handler))
+	defer srv.Close()
+
+	srvURL, err := url.Parse(srv.URL)
+	require.NoError(t, err)
+	srvPort, err := strconv.ParseInt(srvURL.Port(), 10, 32)
+	require.NoError(t, err)
+
+	resp, err := srv.Client().Get(srv.URL)
+	require.NoError(t, err)
+	require.NoError(t, resp.Body.Close())
+
+	req := <-got
+	peer, peerPort := semconv.SplitHostPort(req.RemoteAddr)
+
+	const user = "alice"
+	req.SetBasicAuth(user, "pswrd")
+
+	const clientIP = "127.0.0.5"
+	req.Header.Add("X-Forwarded-For", clientIP)
+
+	srvReq := testServerReq{
+		hostname:   srvURL.Hostname(),
+		serverPort: int(srvPort),
+		peerAddr:   peer,
+		peerPort:   peerPort,
+		clientIP:   clientIP,
+	}
+
+	assert.ElementsMatch(t, want(srvReq), serv.RequestTraceAttrs("", req, semconv.RequestTraceAttrsOpts{}))
+}

pkg/gotenberg/semconv/doc.go

@@ -0,0 +1,7 @@
+// Package semconv is a copy/paste of utilities that are currently not exposed
+// in the OpenTelemery Go SDK.
+//
+// This package MUST be removed once an "official" API is provided.
+//
+// See: https://github.com/open-telemetry/opentelemetry-go-contrib/issues/4580.
+package semconv

pkg/gotenberg/semconv/gen.go

@@ -0,0 +1,15 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp/internal/semconv"
+
+// Generate semconv package:
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/bench_test.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=bench_test.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/common_test.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=common_test.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/server.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=server.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/server_test.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=server_test.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/client.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=client.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/client_test.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=client_test.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/httpconvtest_test.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=httpconvtest_test.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/util.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=util.go
+//go:generate gotmpl --body=../../../../../../internal/shared/semconv/util_test.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp\" }" --out=util_test.go

pkg/gotenberg/semconv/httpconvtest_test.go

@@ -0,0 +1,455 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/httpconv_test.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv_test
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg/semconv"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/sdk/instrumentation"
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest"
+)
+
+func TestNewTraceRequest(t *testing.T) {
+	serv := semconv.NewHTTPServer(nil)
+	want := func(req testServerReq) []attribute.KeyValue {
+		return []attribute.KeyValue{
+			attribute.String("http.request.method", "GET"),
+			attribute.String("url.scheme", "http"),
+			attribute.String("server.address", req.hostname),
+			attribute.Int("server.port", req.serverPort),
+			attribute.String("network.peer.address", req.peerAddr),
+			attribute.Int("network.peer.port", req.peerPort),
+			attribute.String("user_agent.original", "Go-http-client/1.1"),
+			attribute.String("client.address", req.clientIP),
+			attribute.String("network.protocol.version", "1.1"),
+			attribute.String("url.path", "/"),
+		}
+	}
+	testTraceRequest(t, serv, want)
+}
+
+func TestNewServerRecordMetrics(t *testing.T) {
+	oldAttrs := attribute.NewSet(
+		attribute.String("http.scheme", "http"),
+		attribute.String("http.method", "POST"),
+		attribute.Int64("http.status_code", 301),
+		attribute.String("key", "value"),
+		attribute.String("net.host.name", "stuff"),
+		attribute.String("net.protocol.name", "http"),
+		attribute.String("net.protocol.version", "1.1"),
+	)
+
+	currAttrs := attribute.NewSet(
+		attribute.String("http.request.method", "POST"),
+		attribute.Int64("http.response.status_code", 301),
+		attribute.String("key", "value"),
+		attribute.String("network.protocol.name", "http"),
+		attribute.String("network.protocol.version", "1.1"),
+		attribute.String("server.address", "stuff"),
+		attribute.String("url.scheme", "http"),
+	)
+
+	// the HTTPServer version
+	expectedCurrentScopeMetric := metricdata.ScopeMetrics{
+		Scope: instrumentation.Scope{
+			Name: "test",
+		},
+		Metrics: []metricdata.Metrics{
+			{
+				Name:        "http.server.request.body.size",
+				Description: "Size of HTTP server request bodies.",
+				Unit:        "By",
+				Data: metricdata.Histogram[int64]{
+					Temporality: metricdata.CumulativeTemporality,
+					DataPoints: []metricdata.HistogramDataPoint[int64]{
+						{
+							Attributes: currAttrs,
+						},
+					},
+				},
+			},
+			{
+				Name:        "http.server.response.body.size",
+				Description: "Size of HTTP server response bodies.",
+				Unit:        "By",
+				Data: metricdata.Histogram[int64]{
+					Temporality: metricdata.CumulativeTemporality,
+					DataPoints: []metricdata.HistogramDataPoint[int64]{
+						{
+							Attributes: currAttrs,
+						},
+					},
+				},
+			},
+			{
+				Name:        "http.server.request.duration",
+				Description: "Duration of HTTP server requests.",
+				Unit:        "s",
+				Data: metricdata.Histogram[float64]{
+					Temporality: metricdata.CumulativeTemporality,
+					DataPoints: []metricdata.HistogramDataPoint[float64]{
+						{
+							Attributes: currAttrs,
+						},
+					},
+				},
+			},
+		},
+	}
+
+	// The OldHTTPServer version
+	expectedOldScopeMetric := expectedCurrentScopeMetric
+	expectedOldScopeMetric.Metrics = append(expectedOldScopeMetric.Metrics, []metricdata.Metrics{
+		{
+			Name:        "http.server.request.size",
+			Description: "Measures the size of HTTP request messages.",
+			Unit:        "By",
+			Data: metricdata.Sum[int64]{
+				Temporality: metricdata.CumulativeTemporality,
+				IsMonotonic: true,
+				DataPoints: []metricdata.DataPoint[int64]{
+					{
+						Attributes: oldAttrs,
+					},
+				},
+			},
+		},
+		{
+			Name:        "http.server.response.size",
+			Description: "Measures the size of HTTP response messages.",
+			Unit:        "By",
+			Data: metricdata.Sum[int64]{
+				Temporality: metricdata.CumulativeTemporality,
+				IsMonotonic: true,
+				DataPoints: []metricdata.DataPoint[int64]{
+					{
+						Attributes: oldAttrs,
+					},
+				},
+			},
+		},
+		{
+			Name:        "http.server.duration",
+			Description: "Measures the duration of inbound HTTP requests.",
+			Unit:        "ms",
+			Data: metricdata.Histogram[float64]{
+				Temporality: metricdata.CumulativeTemporality,
+				DataPoints: []metricdata.HistogramDataPoint[float64]{
+					{
+						Attributes: oldAttrs,
+					},
+				},
+			},
+		},
+	}...)
+
+	tests := []struct {
+		name       string
+		serverFunc func(metric.MeterProvider) semconv.HTTPServer
+		wantFunc   func(t *testing.T, rm metricdata.ResourceMetrics)
+	}{
+		{
+			name: "No Meter",
+			serverFunc: func(metric.MeterProvider) semconv.HTTPServer {
+				return semconv.NewHTTPServer(nil)
+			},
+			wantFunc: func(t *testing.T, rm metricdata.ResourceMetrics) {
+				assert.Empty(t, rm.ScopeMetrics)
+			},
+		},
+		{
+			name: "With Meter",
+			serverFunc: func(mp metric.MeterProvider) semconv.HTTPServer {
+				return semconv.NewHTTPServer(mp.Meter("test"))
+			},
+			wantFunc: func(t *testing.T, rm metricdata.ResourceMetrics) {
+				require.Len(t, rm.ScopeMetrics, 1)
+
+				// because of OldHTTPServer
+				require.Len(t, rm.ScopeMetrics[0].Metrics, 3)
+				metricdatatest.AssertEqual(t, expectedCurrentScopeMetric, rm.ScopeMetrics[0], metricdatatest.IgnoreTimestamp(), metricdatatest.IgnoreValue())
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			reader := sdkmetric.NewManualReader()
+			mp := sdkmetric.NewMeterProvider(sdkmetric.WithReader(reader))
+
+			server := tt.serverFunc(mp)
+			req, err := http.NewRequest("POST", "http://example.com", http.NoBody)
+			assert.NoError(t, err)
+
+			server.RecordMetrics(t.Context(), semconv.ServerMetricData{
+				ServerName:   "stuff",
+				ResponseSize: 200,
+				MetricAttributes: semconv.MetricAttributes{
+					Req:        req,
+					StatusCode: 301,
+					AdditionalAttributes: []attribute.KeyValue{
+						attribute.String("key", "value"),
+					},
+				},
+				MetricData: semconv.MetricData{
+					RequestSize: 100,
+					ElapsedTime: 300,
+				},
+			})
+
+			rm := metricdata.ResourceMetrics{}
+			require.NoError(t, reader.Collect(t.Context(), &rm))
+			tt.wantFunc(t, rm)
+		})
+	}
+}
+
+func TestNewTraceResponse(t *testing.T) {
+	testCases := []struct {
+		name string
+		resp semconv.ResponseTelemetry
+		want []attribute.KeyValue
+	}{
+		{
+			name: "empty",
+			resp: semconv.ResponseTelemetry{},
+			want: nil,
+		},
+		{
+			name: "no errors",
+			resp: semconv.ResponseTelemetry{
+				StatusCode: 200,
+				ReadBytes:  701,
+				WriteBytes: 802,
+			},
+			want: []attribute.KeyValue{
+				attribute.Int("http.request.body.size", 701),
+				attribute.Int("http.response.body.size", 802),
+				attribute.Int("http.response.status_code", 200),
+			},
+		},
+		{
+			name: "with errors",
+			resp: semconv.ResponseTelemetry{
+				StatusCode: 200,
+				ReadBytes:  701,
+				ReadError:  fmt.Errorf("read error"),
+				WriteBytes: 802,
+				WriteError: fmt.Errorf("write error"),
+			},
+			want: []attribute.KeyValue{
+				attribute.Int("http.request.body.size", 701),
+				attribute.Int("http.response.body.size", 802),
+				attribute.Int("http.response.status_code", 200),
+			},
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			got := semconv.HTTPServer{}.ResponseTraceAttrs(tt.resp)
+			assert.ElementsMatch(t, tt.want, got)
+		})
+	}
+}
+
+func TestNewTraceRequest_Client(t *testing.T) {
+	body := strings.NewReader("Hello, world!")
+	url := "https://example.com:8888/foo/bar?stuff=morestuff"
+	req := httptest.NewRequest("pOST", url, body)
+	req.Header.Set("User-Agent", "go-test-agent")
+
+	want := []attribute.KeyValue{
+		attribute.String("http.request.method", "POST"),
+		attribute.String("http.request.method_original", "pOST"),
+		attribute.String("url.full", url),
+		attribute.String("server.address", "example.com"),
+		attribute.Int("server.port", 8888),
+		attribute.String("network.protocol.version", "1.1"),
+	}
+	client := semconv.NewHTTPClient(nil)
+	assert.ElementsMatch(t, want, client.RequestTraceAttrs(req))
+}
+
+func TestNewTraceResponse_Client(t *testing.T) {
+	testcases := []struct {
+		resp http.Response
+		want []attribute.KeyValue
+	}{
+		{resp: http.Response{StatusCode: 200, ContentLength: 123}, want: []attribute.KeyValue{attribute.Int("http.response.status_code", 200)}},
+		{resp: http.Response{StatusCode: 404, ContentLength: 0}, want: []attribute.KeyValue{attribute.Int("http.response.status_code", 404), attribute.String("error.type", "404")}},
+	}
+
+	for _, tt := range testcases {
+		client := semconv.NewHTTPClient(nil)
+		assert.ElementsMatch(t, tt.want, client.ResponseTraceAttrs(&tt.resp))
+	}
+}
+
+func TestClientRequest(t *testing.T) {
+	body := strings.NewReader("Hello, world!")
+	url := "https://example.com:8888/foo/bar?stuff=morestuff"
+	req := httptest.NewRequest("pOST", url, body)
+	req.Header.Set("User-Agent", "go-test-agent")
+
+	want := []attribute.KeyValue{
+		attribute.String("http.request.method", "POST"),
+		attribute.String("http.request.method_original", "pOST"),
+		attribute.String("url.full", url),
+		attribute.String("server.address", "example.com"),
+		attribute.Int("server.port", 8888),
+		attribute.String("network.protocol.version", "1.1"),
+	}
+	got := semconv.HTTPClient{}.RequestTraceAttrs(req)
+	assert.ElementsMatch(t, want, got)
+}
+
+func TestClientResponse(t *testing.T) {
+	testcases := []struct {
+		resp http.Response
+		want []attribute.KeyValue
+	}{
+		{resp: http.Response{StatusCode: 200, ContentLength: 123}, want: []attribute.KeyValue{attribute.Int("http.response.status_code", 200)}},
+		{resp: http.Response{StatusCode: 404, ContentLength: 0}, want: []attribute.KeyValue{attribute.Int("http.response.status_code", 404), attribute.String("error.type", "404")}},
+	}
+
+	for _, tt := range testcases {
+		got := semconv.HTTPClient{}.ResponseTraceAttrs(&tt.resp)
+		assert.ElementsMatch(t, tt.want, got)
+	}
+}
+
+func TestRequestErrorType(t *testing.T) {
+	testcases := []struct {
+		err  error
+		want attribute.KeyValue
+	}{
+		{err: errors.New("http: nil Request.URL"), want: attribute.String("error.type", "*errors.errorString")},
+		{err: customError{}, want: attribute.String("error.type", "github.com/gotenberg/gotenberg/v8/pkg/gotenberg/semconv_test.customError")},
+	}
+
+	for _, tt := range testcases {
+		got := semconv.HTTPClient{}.ErrorType(tt.err)
+		assert.Equal(t, tt.want, got)
+	}
+}
+
+func TestNewClientRecordMetrics(t *testing.T) {
+	currAttrs := attribute.NewSet(
+		attribute.String("http.request.method", "POST"),
+		attribute.Int64("http.response.status_code", 301),
+		attribute.String("network.protocol.name", "http"),
+		attribute.String("network.protocol.version", "1.1"),
+		attribute.String("server.address", "example.com"),
+		attribute.String("url.scheme", "http"),
+	)
+
+	// the HTTPClient version
+	expectedCurrentScopeMetric := metricdata.ScopeMetrics{
+		Scope: instrumentation.Scope{
+			Name: "test",
+		},
+		Metrics: []metricdata.Metrics{
+			{
+				Name:        "http.client.request.body.size",
+				Description: "Size of HTTP client request bodies.",
+				Unit:        "By",
+				Data: metricdata.Histogram[int64]{
+					Temporality: metricdata.CumulativeTemporality,
+					DataPoints: []metricdata.HistogramDataPoint[int64]{
+						{
+							Attributes: currAttrs,
+						},
+					},
+				},
+			},
+			{
+				Name:        "http.client.request.duration",
+				Description: "Duration of HTTP client requests.",
+				Unit:        "s",
+				Data: metricdata.Histogram[float64]{
+					Temporality: metricdata.CumulativeTemporality,
+					DataPoints: []metricdata.HistogramDataPoint[float64]{
+						{
+							Attributes: currAttrs,
+						},
+					},
+				},
+			},
+		},
+	}
+
+	tests := []struct {
+		name       string
+		clientFunc func(metric.MeterProvider) semconv.HTTPClient
+		wantFunc   func(t *testing.T, rm metricdata.ResourceMetrics)
+	}{
+		{
+			name: "No environment variable set, and no Meter",
+			clientFunc: func(metric.MeterProvider) semconv.HTTPClient {
+				return semconv.NewHTTPClient(nil)
+			},
+			wantFunc: func(t *testing.T, rm metricdata.ResourceMetrics) {
+				assert.Empty(t, rm.ScopeMetrics)
+			},
+		},
+		{
+			name: "With Meter",
+			clientFunc: func(mp metric.MeterProvider) semconv.HTTPClient {
+				return semconv.NewHTTPClient(mp.Meter("test"))
+			},
+			wantFunc: func(t *testing.T, rm metricdata.ResourceMetrics) {
+				require.Len(t, rm.ScopeMetrics, 1)
+
+				require.Len(t, rm.ScopeMetrics[0].Metrics, 2)
+				metricdatatest.AssertEqual(t, expectedCurrentScopeMetric, rm.ScopeMetrics[0], metricdatatest.IgnoreTimestamp(), metricdatatest.IgnoreValue())
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			reader := sdkmetric.NewManualReader()
+			mp := sdkmetric.NewMeterProvider(sdkmetric.WithReader(reader))
+
+			client := tt.clientFunc(mp)
+			req, err := http.NewRequest("POST", "http://example.com", http.NoBody)
+			assert.NoError(t, err)
+
+			client.RecordMetrics(t.Context(), semconv.MetricData{
+				RequestSize: 100,
+				ElapsedTime: 300,
+			}, client.MetricOptions(semconv.MetricAttributes{
+				Req:        req,
+				StatusCode: 301,
+			}))
+
+			rm := metricdata.ResourceMetrics{}
+			require.NoError(t, reader.Collect(t.Context(), &rm))
+			tt.wantFunc(t, rm)
+		})
+	}
+}
+
+type customError struct{}
+
+func (customError) Error() string {
+	return "custom error"
+}

pkg/gotenberg/semconv/server.go

@@ -0,0 +1,405 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/server.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package semconv provides OpenTelemetry semantic convention types and
+// functionality.
+package semconv // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp/internal/semconv"
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"slices"
+	"strings"
+	"sync"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/semconv/v1.39.0"
+	"go.opentelemetry.io/otel/semconv/v1.39.0/httpconv"
+)
+
+type RequestTraceAttrsOpts struct {
+	// If set, this is used as value for the "http.client_ip" attribute.
+	HTTPClientIP string
+}
+
+type ResponseTelemetry struct {
+	StatusCode int
+	ReadBytes  int64
+	ReadError  error
+	WriteBytes int64
+	WriteError error
+}
+
+type HTTPServer struct {
+	requestBodySizeHistogram  httpconv.ServerRequestBodySize
+	responseBodySizeHistogram httpconv.ServerResponseBodySize
+	requestDurationHistogram  httpconv.ServerRequestDuration
+}
+
+func NewHTTPServer(meter metric.Meter) HTTPServer {
+	server := HTTPServer{}
+
+	var err error
+	server.requestBodySizeHistogram, err = httpconv.NewServerRequestBodySize(meter)
+	handleErr(err)
+
+	server.responseBodySizeHistogram, err = httpconv.NewServerResponseBodySize(meter)
+	handleErr(err)
+
+	server.requestDurationHistogram, err = httpconv.NewServerRequestDuration(
+		meter,
+		metric.WithExplicitBucketBoundaries(
+			0.005, 0.01, 0.025, 0.05, 0.075, 0.1,
+			0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10,
+		),
+	)
+	handleErr(err)
+	return server
+}
+
+// Status returns a span status code and message for an HTTP status code
+// value returned by a server.
+func (n HTTPServer) Status(code int) (codes.Code, string) {
+	if code == 0 {
+		return codes.Error, "No HTTP status code"
+	}
+	if code < 100 || code >= 600 {
+		return codes.Error, fmt.Sprintf("Invalid HTTP status code %d", code)
+	}
+	if code >= 400 {
+		return codes.Error, http.StatusText(code)
+	}
+	return codes.Ok, ""
+}
+
+// RequestTraceAttrs returns trace attributes for an HTTP request received by a
+// server.
+//
+// The server must be the primary server name if it is known. For example this
+// would be the ServerName directive
+// (https://httpd.apache.org/docs/2.4/mod/core.html#servername) for an Apache
+// server, and the server_name directive
+// (http://nginx.org/en/docs/http/ngx_http_core_module.html#server_name) for an
+// nginx server. More generically, the primary server name would be the host
+// header value that matches the default virtual host of an HTTP server. It
+// should include the host identifier and if a port is used to route to the
+// server that port identifier should be included as an appropriate port
+// suffix.
+//
+// If the primary server name is not known, server should be an empty string.
+// The req Host will be used to determine the server instead.
+func (n HTTPServer) RequestTraceAttrs(server string, req *http.Request, opts RequestTraceAttrsOpts) []attribute.KeyValue {
+	count := 3 // ServerAddress, Method, Scheme
+
+	var host string
+	var p int
+	if server == "" {
+		host, p = SplitHostPort(req.Host)
+	} else {
+		// Prioritize the primary server name.
+		host, p = SplitHostPort(server)
+		if p < 0 {
+			_, p = SplitHostPort(req.Host)
+		}
+	}
+
+	hostPort := requiredHTTPPort(req.TLS != nil, p)
+	if hostPort > 0 {
+		count++
+	}
+
+	method, methodOriginal := n.method(req.Method)
+	if methodOriginal != (attribute.KeyValue{}) {
+		count++
+	}
+
+	scheme := n.scheme(req.TLS != nil)
+
+	peer, peerPort := SplitHostPort(req.RemoteAddr)
+	if peer != "" {
+		// The Go HTTP server sets RemoteAddr to "IP:port", this will not be a
+		// file-path that would be interpreted with a sock family.
+		count++
+		if peerPort > 0 {
+			count++
+		}
+	}
+
+	useragent := req.UserAgent()
+	if useragent != "" {
+		count++
+	}
+
+	// For client IP, use, in order:
+	// 1. The value passed in the options
+	// 2. The value in the X-Forwarded-For header
+	// 3. The peer address
+	clientIP := opts.HTTPClientIP
+	if clientIP == "" {
+		clientIP = serverClientIP(req.Header.Get("X-Forwarded-For"))
+		if clientIP == "" {
+			clientIP = peer
+		}
+	}
+	if clientIP != "" {
+		count++
+	}
+
+	if req.URL != nil && req.URL.Path != "" {
+		count++
+	}
+
+	protoName, protoVersion := netProtocol(req.Proto)
+	if protoName != "" && protoName != "http" {
+		count++
+	}
+	if protoVersion != "" {
+		count++
+	}
+
+	route := httpRoute(req.Pattern)
+	if route != "" {
+		count++
+	}
+
+	attrs := make([]attribute.KeyValue, 0, count)
+	attrs = append(attrs,
+		semconv.ServerAddress(host),
+		method,
+		scheme,
+	)
+
+	if hostPort > 0 {
+		attrs = append(attrs, semconv.ServerPort(hostPort))
+	}
+	if methodOriginal != (attribute.KeyValue{}) {
+		attrs = append(attrs, methodOriginal)
+	}
+
+	if peer, peerPort := SplitHostPort(req.RemoteAddr); peer != "" {
+		// The Go HTTP server sets RemoteAddr to "IP:port", this will not be a
+		// file-path that would be interpreted with a sock family.
+		attrs = append(attrs, semconv.NetworkPeerAddress(peer))
+		if peerPort > 0 {
+			attrs = append(attrs, semconv.NetworkPeerPort(peerPort))
+		}
+	}
+
+	if useragent != "" {
+		attrs = append(attrs, semconv.UserAgentOriginal(useragent))
+	}
+
+	if clientIP != "" {
+		attrs = append(attrs, semconv.ClientAddress(clientIP))
+	}
+
+	if req.URL != nil && req.URL.Path != "" {
+		attrs = append(attrs, semconv.URLPath(req.URL.Path))
+	}
+
+	if protoName != "" && protoName != "http" {
+		attrs = append(attrs, semconv.NetworkProtocolName(protoName))
+	}
+	if protoVersion != "" {
+		attrs = append(attrs, semconv.NetworkProtocolVersion(protoVersion))
+	}
+
+	if route != "" {
+		attrs = append(attrs, n.Route(route))
+	}
+
+	return attrs
+}
+
+func (s HTTPServer) NetworkTransportAttr(network string) []attribute.KeyValue {
+	attr := semconv.NetworkTransportPipe
+	switch network {
+	case "tcp", "tcp4", "tcp6":
+		attr = semconv.NetworkTransportTCP
+	case "udp", "udp4", "udp6":
+		attr = semconv.NetworkTransportUDP
+	case "unix", "unixgram", "unixpacket":
+		attr = semconv.NetworkTransportUnix
+	}
+
+	return []attribute.KeyValue{attr}
+}
+
+type ServerMetricData struct {
+	ServerName   string
+	ResponseSize int64
+
+	MetricData
+	MetricAttributes
+}
+
+type MetricAttributes struct {
+	Req                  *http.Request
+	StatusCode           int
+	Route                string
+	AdditionalAttributes []attribute.KeyValue
+}
+
+type MetricData struct {
+	RequestSize int64
+
+	// The request duration, in milliseconds
+	ElapsedTime float64
+}
+
+var (
+	metricAddOptionPool = &sync.Pool{
+		New: func() any {
+			return &[]metric.AddOption{}
+		},
+	}
+
+	metricRecordOptionPool = &sync.Pool{
+		New: func() any {
+			return &[]metric.RecordOption{}
+		},
+	}
+)
+
+func (n HTTPServer) RecordMetrics(ctx context.Context, md ServerMetricData) {
+	attributes := n.MetricAttributes(md.ServerName, md.Req, md.StatusCode, md.Route, md.AdditionalAttributes)
+	o := metric.WithAttributeSet(attribute.NewSet(attributes...))
+	recordOpts := metricRecordOptionPool.Get().(*[]metric.RecordOption)
+	*recordOpts = append(*recordOpts, o)
+	n.requestBodySizeHistogram.Inst().Record(ctx, md.RequestSize, *recordOpts...)
+	n.responseBodySizeHistogram.Inst().Record(ctx, md.ResponseSize, *recordOpts...)
+	n.requestDurationHistogram.Inst().Record(ctx, md.ElapsedTime/1000.0, o)
+	*recordOpts = (*recordOpts)[:0]
+	metricRecordOptionPool.Put(recordOpts)
+}
+
+func (n HTTPServer) method(method string) (attribute.KeyValue, attribute.KeyValue) {
+	if method == "" {
+		return semconv.HTTPRequestMethodGet, attribute.KeyValue{}
+	}
+	if attr, ok := methodLookup[method]; ok {
+		return attr, attribute.KeyValue{}
+	}
+
+	orig := semconv.HTTPRequestMethodOriginal(method)
+	if attr, ok := methodLookup[strings.ToUpper(method)]; ok {
+		return attr, orig
+	}
+	return semconv.HTTPRequestMethodGet, orig
+}
+
+func (n HTTPServer) scheme(https bool) attribute.KeyValue { //nolint:revive // ignore linter
+	if https {
+		return semconv.URLScheme("https")
+	}
+	return semconv.URLScheme("http")
+}
+
+// ResponseTraceAttrs returns trace attributes for telemetry from an HTTP
+// response.
+//
+// If any of the fields in the ResponseTelemetry are not set the attribute will
+// be omitted.
+func (n HTTPServer) ResponseTraceAttrs(resp ResponseTelemetry) []attribute.KeyValue {
+	var count int
+
+	if resp.ReadBytes > 0 {
+		count++
+	}
+	if resp.WriteBytes > 0 {
+		count++
+	}
+	if resp.StatusCode > 0 {
+		count++
+	}
+
+	attributes := make([]attribute.KeyValue, 0, count)
+
+	if resp.ReadBytes > 0 {
+		attributes = append(attributes,
+			semconv.HTTPRequestBodySize(int(resp.ReadBytes)),
+		)
+	}
+	if resp.WriteBytes > 0 {
+		attributes = append(attributes,
+			semconv.HTTPResponseBodySize(int(resp.WriteBytes)),
+		)
+	}
+	if resp.StatusCode > 0 {
+		attributes = append(attributes,
+			semconv.HTTPResponseStatusCode(resp.StatusCode),
+		)
+	}
+
+	return attributes
+}
+
+// Route returns the attribute for the route.
+func (n HTTPServer) Route(route string) attribute.KeyValue {
+	return semconv.HTTPRoute(route)
+}
+
+func (n HTTPServer) MetricAttributes(server string, req *http.Request, statusCode int, route string, additionalAttributes []attribute.KeyValue) []attribute.KeyValue {
+	num := len(additionalAttributes) + 3
+	var host string
+	var p int
+	if server == "" {
+		host, p = SplitHostPort(req.Host)
+	} else {
+		// Prioritize the primary server name.
+		host, p = SplitHostPort(server)
+		if p < 0 {
+			_, p = SplitHostPort(req.Host)
+		}
+	}
+	hostPort := requiredHTTPPort(req.TLS != nil, p)
+	if hostPort > 0 {
+		num++
+	}
+	protoName, protoVersion := netProtocol(req.Proto)
+	if protoName != "" {
+		num++
+	}
+	if protoVersion != "" {
+		num++
+	}
+
+	if statusCode > 0 {
+		num++
+	}
+
+	if route != "" {
+		num++
+	}
+
+	attributes := slices.Grow(additionalAttributes, num)
+	attributes = append(attributes,
+		semconv.HTTPRequestMethodKey.String(standardizeHTTPMethod(req.Method)),
+		n.scheme(req.TLS != nil),
+		semconv.ServerAddress(host))
+
+	if hostPort > 0 {
+		attributes = append(attributes, semconv.ServerPort(hostPort))
+	}
+	if protoName != "" {
+		attributes = append(attributes, semconv.NetworkProtocolName(protoName))
+	}
+	if protoVersion != "" {
+		attributes = append(attributes, semconv.NetworkProtocolVersion(protoVersion))
+	}
+
+	if statusCode > 0 {
+		attributes = append(attributes, semconv.HTTPResponseStatusCode(statusCode))
+	}
+
+	if route != "" {
+		attributes = append(attributes, semconv.HTTPRoute(route))
+	}
+	return attributes
+}

pkg/gotenberg/semconv/server_test.go

@@ -0,0 +1,210 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/server_test.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+func TestHTTPServer_MetricAttributes(t *testing.T) {
+	defaultRequest, err := http.NewRequest("GET", "http://example.com/path?query=test", http.NoBody)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name                 string
+		server               string
+		req                  *http.Request
+		statusCode           int
+		route                string
+		additionalAttributes []attribute.KeyValue
+		wantFunc             func(t *testing.T, attrs []attribute.KeyValue)
+	}{
+		{
+			name:                 "routine testing",
+			server:               "",
+			req:                  defaultRequest,
+			statusCode:           200,
+			route:                "",
+			additionalAttributes: []attribute.KeyValue{attribute.String("test", "test")},
+			wantFunc: func(t *testing.T, attrs []attribute.KeyValue) {
+				require.Len(t, attrs, 7)
+				assert.ElementsMatch(t, []attribute.KeyValue{
+					attribute.String("http.request.method", "GET"),
+					attribute.String("url.scheme", "http"),
+					attribute.String("server.address", "example.com"),
+					attribute.String("network.protocol.name", "http"),
+					attribute.String("network.protocol.version", "1.1"),
+					attribute.Int64("http.response.status_code", 200),
+					attribute.String("test", "test"),
+				}, attrs)
+			},
+		},
+		{
+			name:                 "use server address",
+			server:               "example.com:9999",
+			req:                  defaultRequest,
+			statusCode:           200,
+			route:                "/path/${id}",
+			additionalAttributes: nil,
+			wantFunc: func(t *testing.T, attrs []attribute.KeyValue) {
+				require.Len(t, attrs, 8)
+				assert.ElementsMatch(t, []attribute.KeyValue{
+					attribute.String("http.request.method", "GET"),
+					attribute.String("url.scheme", "http"),
+					attribute.String("server.address", "example.com"),
+					attribute.Int("server.port", 9999),
+					attribute.String("network.protocol.name", "http"),
+					attribute.String("network.protocol.version", "1.1"),
+					attribute.Int64("http.response.status_code", 200),
+					attribute.String("http.route", "/path/${id}"),
+				}, attrs)
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := HTTPServer{}.MetricAttributes(tt.server, tt.req, tt.statusCode, tt.route, tt.additionalAttributes)
+			tt.wantFunc(t, got)
+		})
+	}
+}
+
+func TestNewMethod(t *testing.T) {
+	testCases := []struct {
+		method   string
+		n        int
+		want     attribute.KeyValue
+		wantOrig attribute.KeyValue
+	}{
+		{
+			method: http.MethodPost,
+			n:      1,
+			want:   attribute.String("http.request.method", "POST"),
+		},
+		{
+			method:   "Put",
+			n:        2,
+			want:     attribute.String("http.request.method", "PUT"),
+			wantOrig: attribute.String("http.request.method_original", "Put"),
+		},
+		{
+			method:   "Unknown",
+			n:        2,
+			want:     attribute.String("http.request.method", "GET"),
+			wantOrig: attribute.String("http.request.method_original", "Unknown"),
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.method, func(t *testing.T) {
+			got, gotOrig := HTTPServer{}.method(tt.method)
+			assert.Equal(t, tt.want, got)
+			assert.Equal(t, tt.wantOrig, gotOrig)
+		})
+	}
+}
+
+func TestRequestTraceAttrs_HTTPRoute(t *testing.T) {
+	tests := []struct {
+		name      string
+		pattern   string
+		wantRoute string
+	}{
+		{
+			name:      "only path",
+			pattern:   "/path/{id}",
+			wantRoute: "/path/{id}",
+		},
+		{
+			name:      "with method",
+			pattern:   "GET /path/{id}",
+			wantRoute: "/path/{id}",
+		},
+		{
+			name:      "with domain",
+			pattern:   "example.com/path/{id}",
+			wantRoute: "/path/{id}",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodGet, "/path/abc123", http.NoBody)
+			req.Pattern = tt.pattern
+
+			attrs := (HTTPServer{}).RequestTraceAttrs("", req, RequestTraceAttrsOpts{})
+
+			var gotRoute string
+			for _, attr := range attrs {
+				if attr.Key == "http.route" {
+					gotRoute = attr.Value.AsString()
+					break
+				}
+			}
+			require.Equal(t, tt.wantRoute, gotRoute)
+		})
+	}
+}
+
+func TestRequestTraceAttrs_ClientIP(t *testing.T) {
+	for _, tt := range []struct {
+		name              string
+		requestModifierFn func(r *http.Request)
+		requestTraceOpts  RequestTraceAttrsOpts
+
+		wantClientIP string
+	}{
+		{
+			name:         "with a client IP from the network",
+			wantClientIP: "1.2.3.4",
+		},
+		{
+			name: "with a client IP from x-forwarded-for header",
+			requestModifierFn: func(r *http.Request) {
+				r.Header.Add("X-Forwarded-For", "5.6.7.8")
+			},
+			wantClientIP: "5.6.7.8",
+		},
+		{
+			name: "with a client IP in options",
+			requestModifierFn: func(r *http.Request) {
+				r.Header.Add("X-Forwarded-For", "5.6.7.8")
+			},
+			requestTraceOpts: RequestTraceAttrsOpts{
+				HTTPClientIP: "9.8.7.6",
+			},
+			wantClientIP: "9.8.7.6",
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodGet, "/example", http.NoBody)
+			req.RemoteAddr = "1.2.3.4:5678"
+
+			if tt.requestModifierFn != nil {
+				tt.requestModifierFn(req)
+			}
+
+			var found bool
+			for _, attr := range (HTTPServer{}).RequestTraceAttrs("", req, tt.requestTraceOpts) {
+				if attr.Key != "client.address" {
+					continue
+				}
+				found = true
+				assert.Equal(t, tt.wantClientIP, attr.Value.AsString())
+			}
+			require.True(t, found)
+		})
+	}
+}

pkg/gotenberg/semconv/util.go

@@ -0,0 +1,127 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/util.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp/internal/semconv"
+
+import (
+	"net"
+	"net/http"
+	"strconv"
+	"strings"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	semconvNew "go.opentelemetry.io/otel/semconv/v1.39.0"
+)
+
+// SplitHostPort splits a network address hostport of the form "host",
+// "host%zone", "[host]", "[host%zone], "host:port", "host%zone:port",
+// "[host]:port", "[host%zone]:port", or ":port" into host or host%zone and
+// port.
+//
+// An empty host is returned if it is not provided or unparsable. A negative
+// port is returned if it is not provided or unparsable.
+func SplitHostPort(hostport string) (host string, port int) {
+	port = -1
+
+	if strings.HasPrefix(hostport, "[") {
+		addrEnd := strings.LastIndexByte(hostport, ']')
+		if addrEnd < 0 {
+			// Invalid hostport.
+			return
+		}
+		if i := strings.LastIndexByte(hostport[addrEnd:], ':'); i < 0 {
+			host = hostport[1:addrEnd]
+			return
+		}
+	} else {
+		if i := strings.LastIndexByte(hostport, ':'); i < 0 {
+			host = hostport
+			return
+		}
+	}
+
+	host, pStr, err := net.SplitHostPort(hostport)
+	if err != nil {
+		return
+	}
+
+	p, err := strconv.ParseUint(pStr, 10, 16)
+	if err != nil {
+		return
+	}
+	return host, int(p) //nolint:gosec  // Byte size checked 16 above.
+}
+
+func requiredHTTPPort(https bool, port int) int { //nolint:revive // ignore linter
+	if https {
+		if port > 0 && port != 443 {
+			return port
+		}
+	} else {
+		if port > 0 && port != 80 {
+			return port
+		}
+	}
+	return -1
+}
+
+func serverClientIP(xForwardedFor string) string {
+	if idx := strings.IndexByte(xForwardedFor, ','); idx >= 0 {
+		xForwardedFor = xForwardedFor[:idx]
+	}
+	return xForwardedFor
+}
+
+func httpRoute(pattern string) string {
+	if idx := strings.IndexByte(pattern, '/'); idx >= 0 {
+		return pattern[idx:]
+	}
+	return ""
+}
+
+func netProtocol(proto string) (name string, version string) {
+	name, version, _ = strings.Cut(proto, "/")
+	switch name {
+	case "HTTP":
+		name = "http"
+	case "QUIC":
+		name = "quic"
+	case "SPDY":
+		name = "spdy"
+	default:
+		name = strings.ToLower(name)
+	}
+	return name, version
+}
+
+var methodLookup = map[string]attribute.KeyValue{
+	http.MethodConnect: semconvNew.HTTPRequestMethodConnect,
+	http.MethodDelete:  semconvNew.HTTPRequestMethodDelete,
+	http.MethodGet:     semconvNew.HTTPRequestMethodGet,
+	http.MethodHead:    semconvNew.HTTPRequestMethodHead,
+	http.MethodOptions: semconvNew.HTTPRequestMethodOptions,
+	http.MethodPatch:   semconvNew.HTTPRequestMethodPatch,
+	http.MethodPost:    semconvNew.HTTPRequestMethodPost,
+	http.MethodPut:     semconvNew.HTTPRequestMethodPut,
+	http.MethodTrace:   semconvNew.HTTPRequestMethodTrace,
+}
+
+func handleErr(err error) {
+	if err != nil {
+		otel.Handle(err)
+	}
+}
+
+func standardizeHTTPMethod(method string) string {
+	method = strings.ToUpper(method)
+	switch method {
+	case http.MethodConnect, http.MethodDelete, http.MethodGet, http.MethodHead, http.MethodOptions, http.MethodPatch, http.MethodPost, http.MethodPut, http.MethodTrace:
+	default:
+		method = "_OTHER"
+	}
+	return method
+}

pkg/gotenberg/semconv/util_test.go

@@ -0,0 +1,75 @@
+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/semconv/util_test.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package semconv
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSplitHostPort(t *testing.T) {
+	tests := []struct {
+		hostport string
+		host     string
+		port     int
+	}{
+		{"", "", -1},
+		{":8080", "", 8080},
+		{"127.0.0.1", "127.0.0.1", -1},
+		{"www.example.com", "www.example.com", -1},
+		{"127.0.0.1%25en0", "127.0.0.1%25en0", -1},
+		{"[]", "", -1}, // Ensure this doesn't panic.
+		{"[fe80::1", "", -1},
+		{"[fe80::1]", "fe80::1", -1},
+		{"[fe80::1%25en0]", "fe80::1%25en0", -1},
+		{"[fe80::1]:8080", "fe80::1", 8080},
+		{"[fe80::1]::", "", -1}, // Too many colons.
+		{"127.0.0.1:", "127.0.0.1", -1},
+		{"127.0.0.1:port", "127.0.0.1", -1},
+		{"127.0.0.1:8080", "127.0.0.1", 8080},
+		{"www.example.com:8080", "www.example.com", 8080},
+		{"127.0.0.1%25en0:8080", "127.0.0.1%25en0", 8080},
+	}
+
+	for _, test := range tests {
+		h, p := SplitHostPort(test.hostport)
+		assert.Equal(t, test.host, h, test.hostport)
+		assert.Equal(t, test.port, p, test.hostport)
+	}
+}
+
+func TestStandardizeHTTPMethod(t *testing.T) {
+	tests := []struct {
+		method string
+		want   string
+	}{
+		{"GET", "GET"},
+		{"get", "GET"},
+		{"POST", "POST"},
+		{"post", "POST"},
+		{"PUT", "PUT"},
+		{"put", "PUT"},
+		{"DELETE", "DELETE"},
+		{"delete", "DELETE"},
+		{"HEAD", "HEAD"},
+		{"head", "HEAD"},
+		{"OPTIONS", "OPTIONS"},
+		{"options", "OPTIONS"},
+		{"CONNECT", "CONNECT"},
+		{"connect", "CONNECT"},
+		{"TRACE", "TRACE"},
+		{"trace", "TRACE"},
+		{"PATCH", "PATCH"},
+		{"patch", "PATCH"},
+		{"unknown", "_OTHER"},
+		{"", "_OTHER"},
+	}
+	for _, test := range tests {
+		assert.Equal(t, test.want, standardizeHTTPMethod(test.method))
+	}
+}

pkg/gotenberg/supervisor.go

@@ -4,11 +4,10 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"sync"
 	"sync/atomic"
 	"time"
-
-	"go.uber.org/zap"
 )
 
 // ErrProcessAlreadyRestarting happens if the [ProcessSupervisor] is trying
@@ -28,15 +27,15 @@ var ErrMaximumQueueSizeExceeded = errors.New("maximum queue size exceeded")
 type Process interface {
 	// Start initiates the process and returns an error if the process cannot
 	// be started.
-	Start(logger *zap.Logger) error
+	Start(logger *slog.Logger) error
 
 	// Stop terminates the process and returns an error if the process cannot
 	// be stopped.
-	Stop(logger *zap.Logger) error
+	Stop(logger *slog.Logger) error
 
 	// Healthy checks the health of the process. It returns true if the process
 	// is healthy; otherwise, it returns false.
-	Healthy(logger *zap.Logger) bool
+	Healthy(logger *slog.Logger) bool
 }
 
 // ProcessSupervisor provides methods to manage a [Process], including
@@ -67,17 +66,20 @@ type ProcessSupervisor interface {
 	//
 	// It returns an error if the task cannot be run or if the process state
 	// cannot be managed properly.
-	Run(ctx context.Context, logger *zap.Logger, task func() error) error
+	Run(ctx context.Context, logger *slog.Logger, task func() error) error
 
 	// ReqQueueSize returns the current size of the request queue.
 	ReqQueueSize() int64
 
 	// RestartsCount returns the current number of restart.
 	RestartsCount() int64
+
+	// ActiveTasksCount returns the current number of active tasks.
+	ActiveTasksCount() int64
 }
 
 type processSupervisor struct {
-	logger         *zap.Logger
+	logger         *slog.Logger
 	process        Process
 	maxReqLimit    int64
 	maxQueueSize   int64
@@ -99,7 +101,7 @@ type processSupervisor struct {
 }
 
 // NewProcessSupervisor initializes a new [ProcessSupervisor].
-func NewProcessSupervisor(logger *zap.Logger, process Process, maxReqLimit, maxQueueSize, maxConcurrency int64) ProcessSupervisor {
+func NewProcessSupervisor(logger *slog.Logger, process Process, maxReqLimit, maxQueueSize, maxConcurrency int64) ProcessSupervisor {
 	if maxConcurrency < 1 {
 		maxConcurrency = 1
 	}
@@ -122,38 +124,38 @@ func NewProcessSupervisor(logger *zap.Logger, process Process, maxReqLimit, maxQ
 }
 
 func (s *processSupervisor) Launch() error {
-	s.logger.Debug("start process")
+	s.logger.DebugContext(context.Background(), "start process")
 	err := s.process.Start(s.logger)
 	if err != nil {
 		return fmt.Errorf("start process: %w", err)
 	}
 
 	s.firstStart.Store(true)
-	s.logger.Debug("process successfully started")
+	s.logger.DebugContext(context.Background(), "process successfully started")
 
 	return nil
 }
 
 func (s *processSupervisor) Shutdown() error {
-	s.logger.Debug("shutdown process")
+	s.logger.DebugContext(context.Background(), "shutdown process")
 	err := s.process.Stop(s.logger)
 	if err != nil {
 		return fmt.Errorf("shutdown process: %w", err)
 	}
 
-	s.logger.Debug("process successfully shutdown")
+	s.logger.DebugContext(context.Background(), "process successfully shutdown")
 
 	return nil
 }
 
 func (s *processSupervisor) restart() error {
-	s.logger.Debug("restart process")
+	s.logger.DebugContext(context.Background(), "restart process")
 
 	err := s.Shutdown()
 	if err != nil {
 		// Not necessarily critical — chances are the process is already stopped,
 		// but worth flagging in case it indicates a real issue.
-		s.logger.Warn(fmt.Sprintf("stop process before restart: %s", err))
+		s.logger.WarnContext(context.Background(), fmt.Sprintf("stop process before restart: %s", err))
 	}
 
 	err = s.Launch()
@@ -163,7 +165,7 @@ func (s *processSupervisor) restart() error {
 
 	s.reqCounter.Store(0)
 	s.restartsCounter.Add(1)
-	s.logger.Debug("process successfully restarted")
+	s.logger.DebugContext(context.Background(), "process successfully restarted")
 
 	return nil
 }
@@ -186,7 +188,7 @@ func (s *processSupervisor) Healthy() bool {
 	return s.process.Healthy(s.logger)
 }
 
-func (s *processSupervisor) Run(ctx context.Context, logger *zap.Logger, task func() error) error {
+func (s *processSupervisor) Run(ctx context.Context, logger *slog.Logger, task func() error) error {
 	// Atomically check and increment the queue size to avoid the TOCTOU race
 	// originally reported in https://github.com/gotenberg/gotenberg/issues/951.
 	for {
@@ -219,7 +221,7 @@ func (s *processSupervisor) Run(ctx context.Context, logger *zap.Logger, task fu
 			defer func() {
 				s.activeTasks.Add(-1)
 				if semaphoreOwned {
-					logger.Debug("process lock released")
+					logger.DebugContext(ctx, "process lock released")
 					<-s.semaphore
 				}
 			}()
@@ -243,7 +245,7 @@ func (s *processSupervisor) Run(ctx context.Context, logger *zap.Logger, task fu
 		}()
 
 		if errors.Is(err, ErrProcessAlreadyRestarting) {
-			logger.Debug("process is already restarting, trying to acquire process lock again...")
+			logger.DebugContext(ctx, "process is already restarting, trying to acquire process lock again...")
 			time.Sleep(10 * time.Millisecond)
 			continue
 		}
@@ -255,7 +257,7 @@ func (s *processSupervisor) Run(ctx context.Context, logger *zap.Logger, task fu
 
 // acquireSlot attempts to acquire a semaphore slot, yielding it back if a
 // restart drain is in progress.
-func (s *processSupervisor) acquireSlot(ctx context.Context, logger *zap.Logger) error {
+func (s *processSupervisor) acquireSlot(ctx context.Context, logger *slog.Logger) error {
 	select {
 	case s.semaphore <- struct{}{}:
 		// If a restart drain is in progress, release the slot
@@ -265,11 +267,11 @@ func (s *processSupervisor) acquireSlot(ctx context.Context, logger *zap.Logger)
 			return ErrProcessAlreadyRestarting
 		}
 
-		logger.Debug("process lock acquired")
+		logger.DebugContext(ctx, "process lock acquired")
 
 		return nil
 	case <-ctx.Done():
-		logger.Debug("failed to acquire process lock before deadline")
+		logger.DebugContext(ctx, "failed to acquire process lock before deadline")
 
 		return fmt.Errorf("acquire process lock: %w", ctx.Err())
 	}
@@ -303,7 +305,7 @@ func (s *processSupervisor) ensureHealthy(ctx context.Context) error {
 		return nil
 	}
 
-	s.logger.Debug("process is unhealthy, cannot handle task, restarting...")
+	s.logger.DebugContext(context.Background(), "process is unhealthy, cannot handle task, restarting...")
 
 	if err := s.doRestart(ctx); err != nil {
 		return fmt.Errorf("process restart before task: %w", err)
@@ -316,7 +318,7 @@ func (s *processSupervisor) ensureHealthy(ctx context.Context) error {
 // and, if so, triggers an asynchronous restart. If a restart is initiated, it
 // takes ownership of the caller's semaphore slot (the caller must not release
 // it). Returns true if ownership was taken.
-func (s *processSupervisor) maybeRestartAfterTask(logger *zap.Logger) bool {
+func (s *processSupervisor) maybeRestartAfterTask(logger *slog.Logger) bool {
 	if s.maxReqLimit <= 0 || s.reqCounter.Load() < s.maxReqLimit {
 		return false
 	}
@@ -325,15 +327,15 @@ func (s *processSupervisor) maybeRestartAfterTask(logger *zap.Logger) bool {
 		return false
 	}
 
-	s.logger.Debug("max request limit reached, restarting eagerly...")
+	s.logger.DebugContext(context.Background(), "max request limit reached, restarting eagerly...")
 
 	go func() {
 		restartErr := s.doRestartLocked(context.Background())
 		s.restartMutex.Unlock()
 		if restartErr != nil {
-			s.logger.Error(fmt.Sprintf("process restart after task: %v", restartErr))
+			s.logger.ErrorContext(context.Background(), fmt.Sprintf("process restart after task: %v", restartErr))
 		}
-		logger.Debug("process lock released")
+		logger.DebugContext(context.Background(), "process lock released")
 		<-s.semaphore
 	}()
 
@@ -405,6 +407,10 @@ func (s *processSupervisor) RestartsCount() int64 {
 	return s.restartsCounter.Load()
 }
 
+func (s *processSupervisor) ActiveTasksCount() int64 {
+	return s.activeTasks.Load()
+}
+
 // Interface guards.
 var (
 	_ ProcessSupervisor = (*processSupervisor)(nil)

pkg/gotenberg/supervisor_test.go

@@ -3,12 +3,11 @@ package gotenberg
 import (
 	"context"
 	"errors"
+	"log/slog"
 	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
-
-	"go.uber.org/zap"
 )
 
 func TestProcessSupervisor_Launch(t *testing.T) {
@@ -38,10 +37,10 @@ func TestProcessSupervisor_Launch(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			logger := zap.NewNop()
+			logger := slog.New(slog.DiscardHandler)
 
 			process := &ProcessMock{
-				StartMock: func(logger *zap.Logger) error {
+				StartMock: func(logger *slog.Logger) error {
 					return tc.startError
 				},
 			}
@@ -86,10 +85,10 @@ func TestProcessSupervisor_Shutdown(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			logger := zap.NewNop()
+			logger := slog.New(slog.DiscardHandler)
 
 			process := &ProcessMock{
-				StopMock: func(logger *zap.Logger) error {
+				StopMock: func(logger *slog.Logger) error {
 					return tc.stopError
 				},
 			}
@@ -135,13 +134,13 @@ func TestProcessSupervisor_restart(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			logger := zap.NewNop()
+			logger := slog.New(slog.DiscardHandler)
 
 			process := &ProcessMock{
-				StartMock: func(logger *zap.Logger) error {
+				StartMock: func(logger *slog.Logger) error {
 					return tc.startError
 				},
-				StopMock: func(logger *zap.Logger) error {
+				StopMock: func(logger *slog.Logger) error {
 					return tc.stopError
 				},
 			}
@@ -194,10 +193,10 @@ func TestProcessSupervisor_Healthy(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			logger := zap.NewNop()
+			logger := slog.New(slog.DiscardHandler)
 
 			process := &ProcessMock{
-				HealthyMock: func(logger *zap.Logger) bool {
+				HealthyMock: func(logger *slog.Logger) bool {
 					return tc.processHealthy
 				},
 			}
@@ -365,7 +364,7 @@ func TestProcessSupervisor_Run(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			logger := zap.NewNop()
+			logger := slog.New(slog.DiscardHandler)
 
 			var startCalls, healthyCalls, stopCalls atomic.Int64
 			startCalls.Store(0)
@@ -373,15 +372,15 @@ func TestProcessSupervisor_Run(t *testing.T) {
 			stopCalls.Store(0)
 
 			process := &ProcessMock{
-				StartMock: func(logger *zap.Logger) error {
+				StartMock: func(logger *slog.Logger) error {
 					startCalls.Add(1)
 					return tc.startError
 				},
-				StopMock: func(logger *zap.Logger) error {
+				StopMock: func(logger *slog.Logger) error {
 					stopCalls.Add(1)
 					return nil
 				},
-				HealthyMock: func(logger *zap.Logger) bool {
+				HealthyMock: func(logger *slog.Logger) bool {
 					healthyCalls.Add(1)
 					return tc.processHealthy
 				},
@@ -471,7 +470,7 @@ func TestProcessSupervisor_runWithDeadline(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			ps := NewProcessSupervisor(zap.NewNop(), new(ProcessMock), 0, 0, 1).(*processSupervisor)
+			ps := NewProcessSupervisor(slog.New(slog.DiscardHandler), new(ProcessMock), 0, 0, 1).(*processSupervisor)
 
 			ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 			if tc.ctxDone {
@@ -496,12 +495,12 @@ func TestProcessSupervisor_runWithDeadline(t *testing.T) {
 }
 
 func TestProcessSupervisor_ReqQueueSize(t *testing.T) {
-	logger := zap.NewNop()
+	logger := slog.New(slog.DiscardHandler)
 	process := &ProcessMock{
-		StartMock: func(logger *zap.Logger) error {
+		StartMock: func(logger *slog.Logger) error {
 			return nil
 		},
-		HealthyMock: func(logger *zap.Logger) bool {
+		HealthyMock: func(logger *slog.Logger) bool {
 			return true
 		},
 	}
@@ -553,13 +552,13 @@ func TestProcessSupervisor_ReqQueueSize(t *testing.T) {
 }
 
 func TestProcessSupervisor_QueueSizeCAS(t *testing.T) {
-	logger := zap.NewNop()
+	logger := slog.New(slog.DiscardHandler)
 
 	process := &ProcessMock{
-		StartMock: func(logger *zap.Logger) error {
+		StartMock: func(logger *slog.Logger) error {
 			return nil
 		},
-		HealthyMock: func(logger *zap.Logger) bool {
+		HealthyMock: func(logger *slog.Logger) bool {
 			return true
 		},
 	}
@@ -608,13 +607,13 @@ func TestProcessSupervisor_QueueSizeCAS(t *testing.T) {
 }
 
 func TestProcessSupervisor_QueueSizeIncludesActiveTasks(t *testing.T) {
-	logger := zap.NewNop()
+	logger := slog.New(slog.DiscardHandler)
 
 	process := &ProcessMock{
-		StartMock: func(logger *zap.Logger) error {
+		StartMock: func(logger *slog.Logger) error {
 			return nil
 		},
-		HealthyMock: func(logger *zap.Logger) bool {
+		HealthyMock: func(logger *slog.Logger) bool {
 			return true
 		},
 	}
@@ -698,13 +697,13 @@ func TestProcessSupervisor_RestartsCount(t *testing.T) {
 		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
-			logger := zap.NewNop()
+			logger := slog.New(slog.DiscardHandler)
 
 			process := &ProcessMock{
-				StartMock: func(logger *zap.Logger) error {
+				StartMock: func(logger *slog.Logger) error {
 					return tc.startError
 				},
-				StopMock: func(logger *zap.Logger) error {
+				StopMock: func(logger *slog.Logger) error {
 					return tc.stopError
 				},
 			}
@@ -725,18 +724,18 @@ func TestProcessSupervisor_RestartsCount(t *testing.T) {
 }
 
 func TestProcessSupervisor_ConcurrentRun(t *testing.T) {
-	logger := zap.NewNop()
+	logger := slog.New(slog.DiscardHandler)
 
 	var startCalls atomic.Int64
 	process := &ProcessMock{
-		StartMock: func(logger *zap.Logger) error {
+		StartMock: func(logger *slog.Logger) error {
 			startCalls.Add(1)
 			return nil
 		},
-		StopMock: func(logger *zap.Logger) error {
+		StopMock: func(logger *slog.Logger) error {
 			return nil
 		},
-		HealthyMock: func(logger *zap.Logger) bool {
+		HealthyMock: func(logger *slog.Logger) bool {
 			return true
 		},
 	}
@@ -789,16 +788,16 @@ func TestProcessSupervisor_ConcurrentRun(t *testing.T) {
 }
 
 func TestProcessSupervisor_RestartDrainsAllSlots(t *testing.T) {
-	logger := zap.NewNop()
+	logger := slog.New(slog.DiscardHandler)
 
 	process := &ProcessMock{
-		StartMock: func(logger *zap.Logger) error {
+		StartMock: func(logger *slog.Logger) error {
 			return nil
 		},
-		StopMock: func(logger *zap.Logger) error {
+		StopMock: func(logger *slog.Logger) error {
 			return nil
 		},
-		HealthyMock: func(logger *zap.Logger) bool {
+		HealthyMock: func(logger *slog.Logger) bool {
 			return true
 		},
 	}

pkg/gotenberg/telemetry.go

@@ -0,0 +1,238 @@
+package gotenberg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"sync"
+
+	"github.com/hashicorp/go-retryablehttp"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/trace"
+	"go.uber.org/multierr"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg/internal/log"
+	internalotel "github.com/gotenberg/gotenberg/v8/pkg/gotenberg/internal/otel"
+)
+
+const (
+	AutoLoggingFormat = "auto"
+	JsonLoggingFormat = "json"
+	TextLoggingFormat = "text"
+)
+
+const (
+	ErrorLoggingLevel = "error"
+	WarnLoggingLevel  = "warn"
+	InfoLoggingLevel  = "info"
+	DebugLoggingLevel = "debug"
+)
+
+// TelemetryConfig gathers the configuration data for Gotenberg's telemetry.
+type TelemetryConfig struct {
+	ServiceName    string
+	ServiceVersion string
+
+	LogLevel              string
+	LogFieldsPrefix       string
+	LogStdFormat          string
+	LogStdEnableGcpFields bool
+}
+
+func (cfg TelemetryConfig) slogLevel() slog.Level {
+	var level slog.Level
+	err := level.UnmarshalText([]byte(cfg.LogLevel))
+	if err != nil {
+		return slog.LevelInfo
+	}
+	return level
+}
+
+// Validate validates the telemetry configuration.
+func (cfg TelemetryConfig) Validate() error {
+	var err error
+
+	if cfg.ServiceName == "" {
+		err = multierr.Append(err,
+			errors.New("service name must not be empty"),
+		)
+	}
+
+	if cfg.ServiceVersion == "" {
+		err = multierr.Append(err,
+			errors.New("service version must not be empty"),
+		)
+	}
+
+	switch cfg.LogLevel {
+	case ErrorLoggingLevel, WarnLoggingLevel, InfoLoggingLevel, DebugLoggingLevel:
+		break
+	default:
+		err = multierr.Append(
+			err,
+			fmt.Errorf("log level must be either %s, %s, %s or %s", ErrorLoggingLevel, WarnLoggingLevel, InfoLoggingLevel, DebugLoggingLevel),
+		)
+	}
+
+	switch cfg.LogStdFormat {
+	case AutoLoggingFormat, JsonLoggingFormat, TextLoggingFormat:
+		break
+	default:
+		err = multierr.Append(
+			err,
+			fmt.Errorf("standard log format must be either %s, %s or %s", AutoLoggingFormat, JsonLoggingFormat, TextLoggingFormat),
+		)
+	}
+
+	return err
+}
+
+// StartTelemetry starts the telemetry utilities.
+func StartTelemetry(cfg TelemetryConfig) (shutdown func(context.Context) error, err error) {
+	var handlers []slog.Handler
+
+	stdHandler, err := log.NewStdHandler(cfg.slogLevel(), cfg.LogStdFormat, cfg.LogFieldsPrefix, cfg.LogStdEnableGcpFields)
+	if err != nil {
+		return nil, fmt.Errorf("get standard logger handler: %w", err)
+	}
+	handlers = append(handlers, stdHandler)
+
+	// We need a logger for the other providers.
+	// We'll use the stdHandler for now.
+	bootstrapLogger := slog.New(stdHandler)
+
+	// OpenTelemetry.
+	var shutdowns []func(context.Context) error
+
+	shutdownFn, err := internalotel.InitTracerProvider(bootstrapLogger, cfg.ServiceName, cfg.ServiceVersion)
+	if err != nil {
+		return nil, fmt.Errorf("initialize OpenTelemetry tracer provider: %w", err)
+	}
+	shutdowns = append(shutdowns, shutdownFn)
+
+	shutdownFn, err = internalotel.InitMeterProvider(bootstrapLogger, cfg.ServiceName, cfg.ServiceVersion)
+	if err != nil {
+		return nil, fmt.Errorf("initialize OpenTelemetry meter provider: %w", err)
+	}
+	shutdowns = append(shutdowns, shutdownFn)
+
+	shutdownFn, otelHandler, err := internalotel.InitLoggerProvider(bootstrapLogger, cfg.ServiceName, cfg.ServiceVersion)
+	if err != nil {
+		return nil, fmt.Errorf("initialize OpenTelemetry logger provider: %w", err)
+	}
+	handlers = append(handlers, log.LevelFilter(otelHandler, cfg.slogLevel()))
+	shutdowns = append(shutdowns, shutdownFn)
+
+	// Global logger.
+	log.InitLogger(log.NewGotenbergHandler(log.FanOut(handlers...), cfg.LogFieldsPrefix))
+
+	return func(ctx context.Context) error {
+		filterErr := func(err error) error {
+			if errors.Is(err, context.Canceled) {
+				return nil
+			}
+			return err
+		}
+
+		var wg sync.WaitGroup
+		var errs error
+		var mu sync.Mutex
+
+		for _, fn := range shutdowns {
+			wg.Add(1)
+
+			go func(shutdownFn func(context.Context) error) {
+				defer wg.Done()
+
+				shutdownErr := shutdownFn(ctx)
+				if filterErr(shutdownErr) != nil {
+					mu.Lock()
+					errs = errors.Join(errs, shutdownErr)
+					mu.Unlock()
+				}
+			}(fn)
+		}
+
+		wg.Wait()
+		return errs
+	}, nil
+}
+
+// Logger returns the global logger.
+func Logger(mod Module) *slog.Logger {
+	return log.Logger().With(slog.String("logger", mod.Descriptor().ID))
+}
+
+const (
+	// instrumentationName is the name of the OpenTelemetry instrumentation
+	// library.
+	instrumentationName = "github.com/gotenberg/gotenberg"
+)
+
+// Tracer returns a [trace.Tracer] with the instrumentation name and version
+// already set.
+func Tracer() trace.Tracer {
+	return otel.GetTracerProvider().Tracer(
+		instrumentationName,
+		trace.WithInstrumentationVersion(Version),
+	)
+}
+
+// Meter returns a [metric.Meter] with the instrumentation name and version
+// already set.
+func Meter() metric.Meter {
+	return otel.GetMeterProvider().Meter(
+		instrumentationName,
+		metric.WithInstrumentationVersion(Version),
+	)
+}
+
+// LeveledLogger is a wrapper around a [slog.Logger] so that it may be used by a
+// [retryablehttp.Client].
+type LeveledLogger struct {
+	logger *slog.Logger
+	ctx    context.Context
+}
+
+// NewLeveledLogger instantiates a [LeveledLogger].
+func NewLeveledLogger(logger *slog.Logger) *LeveledLogger {
+	return &LeveledLogger{
+		logger: logger,
+		ctx:    context.Background(),
+	}
+}
+
+// WithContext returns a new [LeveledLogger] with the given context.
+func (leveled LeveledLogger) WithContext(ctx context.Context) *LeveledLogger {
+	return &LeveledLogger{
+		logger: leveled.logger,
+		ctx:    ctx,
+	}
+}
+
+// Error logs a message at the error level using the wrapped slog.Logger.
+func (leveled LeveledLogger) Error(msg string, keysAndValues ...any) {
+	leveled.logger.ErrorContext(leveled.ctx, fmt.Sprintf("%s: %+v", msg, keysAndValues))
+}
+
+// Warn logs a message at the warning level using the wrapped slog.Logger.
+func (leveled LeveledLogger) Warn(msg string, keysAndValues ...any) {
+	leveled.logger.WarnContext(leveled.ctx, fmt.Sprintf("%s: %+v", msg, keysAndValues))
+}
+
+// Info logs a message at the info level using the wrapped slog.Logger.
+func (leveled LeveledLogger) Info(msg string, keysAndValues ...any) {
+	leveled.logger.InfoContext(leveled.ctx, fmt.Sprintf("%s: %+v", msg, keysAndValues))
+}
+
+// Debug logs a message at the debug level using the wrapped slog.Logger.
+func (leveled LeveledLogger) Debug(msg string, keysAndValues ...any) {
+	leveled.logger.DebugContext(leveled.ctx, fmt.Sprintf("%s: %+v", msg, keysAndValues))
+}
+
+// Interface guards.
+var (
+	_ retryablehttp.LeveledLogger = (*LeveledLogger)(nil)
+)

pkg/modules/api/api.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"net"
 	"net/http"
 	"sort"
@@ -15,7 +16,6 @@ import (
 	"github.com/labstack/echo/v4"
 	flag "github.com/spf13/pflag"
 	"go.uber.org/multierr"
-	"go.uber.org/zap"
 	"golang.org/x/net/http2"
 	"golang.org/x/sync/errgroup"
 
@@ -29,20 +29,20 @@ func init() {
 // Api is a module that provides an HTTP server. Other modules may add routes,
 // middlewares or health checks.
 type Api struct {
-	port                      int
-	bindIp                    string
-	tlsCertFile               string
-	tlsKeyFile                string
-	startTimeout              time.Duration
-	bodyLimit                 int64
-	timeout                   time.Duration
-	rootPath                  string
-	traceHeader               string
-	basicAuthUsername         string
-	basicAuthPassword         string
-	downloadFromCfg           downloadFromConfig
-	disableHealthCheckLogging bool
-	enableDebugRoute          bool
+	port                             int
+	bindIp                           string
+	tlsCertFile                      string
+	tlsKeyFile                       string
+	startTimeout                     time.Duration
+	bodyLimit                        int64
+	timeout                          time.Duration
+	rootPath                         string
+	correlationIdHeader              string
+	basicAuthUsername                string
+	basicAuthPassword                string
+	downloadFromCfg                  downloadFromConfig
+	disableHealthCheckRouteTelemetry bool
+	enableDebugRoute                 bool
 
 	routes              []Route
 	externalMiddlewares []Middleware
@@ -50,7 +50,7 @@ type Api struct {
 	readyFn             []func() error
 	asyncCounters       []AsynchronousCounter
 	fs                  *gotenberg.FileSystem
-	logger              *zap.Logger
+	logger              *slog.Logger
 	srv                 *echo.Echo
 }
 
@@ -80,9 +80,10 @@ type Route struct {
 	// Optional.
 	IsMultipart bool
 
-	// DisableLogging disables the logging for this route.
+	// DisableTelemetry disables telemetry (logging, tracing, metrics) for
+	// this route.
 	// Optional.
-	DisableLogging bool
+	DisableTelemetry bool
 
 	// Handler is the function that handles the request.
 	// Required.
@@ -190,14 +191,26 @@ func (a *Api) Descriptor() gotenberg.ModuleDescriptor {
 			fs.Duration("api-timeout", time.Duration(30)*time.Second, "Set the time limit for requests")
 			fs.String("api-body-limit", "", "Set the body limit for multipart/form-data requests - it accepts values like 5MB, 1GB, etc")
 			fs.String("api-root-path", "/", "Set the root path of the API - for service discovery via URL paths")
-			fs.String("api-trace-header", "Gotenberg-Trace", "Set the header name to use for identifying requests")
+			fs.String("api-correlation-id-header", "Gotenberg-Trace", "Set the header name to use for identifying requests")
 			fs.Bool("api-enable-basic-auth", false, "Enable basic authentication - will look for the GOTENBERG_API_BASIC_AUTH_USERNAME and GOTENBERG_API_BASIC_AUTH_PASSWORD environment variables")
 			fs.StringSlice("api-download-from-allow-list", []string{}, "Set the allowed URLs for the download from feature using regular expressions - supports multiple values")
 			fs.StringSlice("api-download-from-deny-list", []string{}, "Set the denied URLs for the download from feature using regular expressions - supports multiple values")
 			fs.Int("api-download-from-max-retry", 4, "Set the maximum number of retries for the download from feature")
 			fs.Bool("api-disable-download-from", false, "Disable the download from feature")
-			fs.Bool("api-disable-health-check-logging", false, "Disable health check logging")
+			fs.Bool("api-disable-health-check-route-telemetry", false, "Disable telemetry for health check route")
 			fs.Bool("api-enable-debug-route", false, "Enable the debug route")
+
+			// Deprecated flags.
+			fs.String("api-trace-header", "Gotenberg-Trace", "Set the header name to use for identifying requests")
+			fs.Bool("api-disable-health-check-logging", false, "Disable health check logging")
+
+			err := errors.Join(
+				fs.MarkDeprecated("api-trace-header", "use --api-correlation-id-header instead"),
+				fs.MarkDeprecated("api-disable-health-check-logging", "use --api-disable-health-check-route-telemetry instead"),
+			)
+			if err != nil {
+				panic(err)
+			}
 			return fs
 		}(),
 		New: func() gotenberg.Module { return new(Api) },
@@ -215,14 +228,14 @@ func (a *Api) Provision(ctx *gotenberg.Context) error {
 	a.timeout = flags.MustDuration("api-timeout")
 	a.bodyLimit = flags.MustHumanReadableBytes("api-body-limit")
 	a.rootPath = flags.MustString("api-root-path")
-	a.traceHeader = flags.MustString("api-trace-header")
+	a.correlationIdHeader = flags.MustDeprecatedString("api-trace-header", "api-correlation-id-header")
 	a.downloadFromCfg = downloadFromConfig{
 		allowList: flags.MustRegexpSlice("api-download-from-allow-list"),
 		denyList:  flags.MustRegexpSlice("api-download-from-deny-list"),
 		maxRetry:  flags.MustInt("api-download-from-max-retry"),
 		disable:   flags.MustBool("api-disable-download-from"),
 	}
-	a.disableHealthCheckLogging = flags.MustBool("api-disable-health-check-logging")
+	a.disableHealthCheckRouteTelemetry = flags.MustDeprecatedBool("api-disable-health-check-logging", "api-disable-health-check-route-telemetry")
 	a.enableDebugRoute = flags.MustBool("api-enable-debug-route")
 
 	// Port from env?
@@ -328,17 +341,7 @@ func (a *Api) Provision(ctx *gotenberg.Context) error {
 	}
 
 	// Logger.
-	loggerProvider, err := ctx.Module(new(gotenberg.LoggerProvider))
-	if err != nil {
-		return fmt.Errorf("get logger provider: %w", err)
-	}
-
-	logger, err := loggerProvider.(gotenberg.LoggerProvider).Logger(a)
-	if err != nil {
-		return fmt.Errorf("get logger: %w", err)
-	}
-
-	a.logger = logger
+	a.logger = gotenberg.Logger(a)
 
 	// File system.
 	a.fs = gotenberg.NewFileSystem(new(gotenberg.OsMkdirAll))
@@ -378,7 +381,7 @@ func (a *Api) Validate() error {
 		)
 	}
 
-	if len(strings.TrimSpace(a.traceHeader)) == 0 {
+	if len(strings.TrimSpace(a.correlationIdHeader)) == 0 {
 		err = multierr.Append(err,
 			errors.New("trace header must not be empty"),
 		)
@@ -442,28 +445,28 @@ func (a *Api) Start() error {
 	a.srv.HTTPErrorHandler = httpErrorHandler()
 
 	// Let's prepare the modules' routes.
-	var disableLoggingForPaths []string
+	var disableTelemetryForPaths []string
 	for i, route := range a.routes {
 		a.routes[i].Path = strings.TrimPrefix(route.Path, "/")
 
-		if route.DisableLogging {
-			disableLoggingForPaths = append(disableLoggingForPaths, strings.TrimPrefix(route.Path, "/"))
+		if route.DisableTelemetry {
+			disableTelemetryForPaths = append(disableTelemetryForPaths, strings.TrimPrefix(route.Path, "/"))
 		}
 	}
 
-	// Check if the user wishes to add logging entries related to the health
-	// check route.
-	if a.disableHealthCheckLogging {
-		disableLoggingForPaths = append(disableLoggingForPaths, "health")
+	// Check if the user wishes to disable telemetry for the health check route.
+	if a.disableHealthCheckRouteTelemetry {
+		disableTelemetryForPaths = append(disableTelemetryForPaths, "health")
 	}
 
+	serverName := fmt.Sprintf("%s:%d", a.bindIp, a.port)
+
 	// Add the API middlewares.
 	a.srv.Pre(
 		latencyMiddleware(),
 		rootPathMiddleware(a.rootPath),
-		traceMiddleware(a.traceHeader),
 		outputFilenameMiddleware(),
-		loggerMiddleware(a.logger, disableLoggingForPaths),
+		telemetryMiddleware(a.logger, serverName, a.correlationIdHeader, disableTelemetryForPaths),
 	)
 
 	// Add the modules' middlewares in their respective stacks.
@@ -535,7 +538,9 @@ func (a *Api) Start() error {
 	)
 
 	// Let's not forget the health check routes...
-	checks := append(a.healthChecks, health.WithTimeout(a.timeout))
+	checks := make([]health.CheckerOption, len(a.healthChecks), len(a.healthChecks)+1)
+	copy(checks, a.healthChecks)
+	checks = append(checks, health.WithTimeout(a.timeout))
 	checker := health.NewChecker(checks...)
 	healthCheckHandler := health.NewHandler(checker)
 
@@ -600,7 +605,7 @@ func (a *Api) Start() error {
 			err = a.srv.StartH2CServer(fmt.Sprintf("%s:%d", a.bindIp, a.port), server)
 		}
 		if !errors.Is(err, http.ErrServerClosed) {
-			a.logger.Fatal(err.Error())
+			a.logger.ErrorContext(context.Background(), err.Error())
 		}
 	}()
 
@@ -627,12 +632,12 @@ func (a *Api) Stop(ctx context.Context) error {
 		case <-ctx.Done():
 			return a.srv.Shutdown(ctx)
 		default:
-			a.logger.Debug(fmt.Sprintf("%d asynchronous requests", count))
+			a.logger.DebugContext(ctx, fmt.Sprintf("%d asynchronous requests", count))
 			if count > 0 {
 				time.Sleep(1 * time.Second)
 				continue
 			}
-			a.logger.Debug("no more asynchronous requests, continue with shutdown")
+			a.logger.DebugContext(ctx, "no more asynchronous requests, continue with shutdown")
 			err := a.srv.Shutdown(ctx)
 			if err != nil {
 				return fmt.Errorf("shutdown: %w", err)

pkg/modules/api/context.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log/slog"
 	"mime"
 	"mime/multipart"
 	"net/http"
@@ -19,7 +20,8 @@ import (
 	"github.com/hashicorp/go-retryablehttp"
 	"github.com/labstack/echo/v4"
 	"github.com/mholt/archives"
-	"go.uber.org/zap"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
 	"golang.org/x/sync/errgroup"
 	"golang.org/x/text/unicode/norm"
 
@@ -36,7 +38,7 @@ var (
 	ErrOutOfBoundsOutputPath = errors.New("output path is not within context's working directory")
 )
 
-// Context is the request context for a "multipart/form-data" requests.
+// Context is the request context for a "multipart/form-data" request.
 type Context struct {
 	dirPath      string
 	values       map[string][]string
@@ -45,7 +47,7 @@ type Context struct {
 	outputPaths  []string
 	cancelled    bool
 
-	logger     *zap.Logger
+	logger     *slog.Logger
 	echoCtx    echo.Context
 	mkdirAll   gotenberg.MkdirAll
 	pathRename gotenberg.PathRename
@@ -92,7 +94,7 @@ type downloadFrom struct {
 }
 
 // newContext returns a [Context] by parsing a "multipart/form-data" request.
-func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSystem, timeout time.Duration, bodyLimit int64, downloadFromCfg downloadFromConfig, traceHeader, trace string) (*Context, context.CancelFunc, error) {
+func newContext(echoCtx echo.Context, logger *slog.Logger, fs *gotenberg.FileSystem, timeout time.Duration, bodyLimit int64, downloadFromCfg downloadFromConfig) (*Context, context.CancelFunc, error) {
 	processCtx, processCancel := context.WithTimeout(echoCtx.Request().Context(), timeout)
 
 	// We want to make sure the multipart/form-data does not exceed a given
@@ -137,12 +139,12 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 
 			err := os.RemoveAll(ctx.dirPath)
 			if err != nil {
-				ctx.logger.Error(fmt.Sprintf("remove context's working directory: %s", err))
+				ctx.logger.ErrorContext(context.Background(), fmt.Sprintf("remove context's working directory: %s", err))
 
 				return
 			}
 
-			ctx.logger.Debug(fmt.Sprintf("'%s' context's working directory removed", ctx.dirPath))
+			ctx.logger.DebugContext(context.Background(), fmt.Sprintf("'%s' context's working directory removed", ctx.dirPath))
 			ctx.cancelled = true
 		}
 	}()
@@ -230,7 +232,7 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 					return fmt.Errorf("filter URL: %w", err)
 				}
 
-				logger.Debug(fmt.Sprintf("download file from '%s'", dl.Url))
+				logger.DebugContext(ctx, fmt.Sprintf("download file from '%s'", dl.Url))
 
 				req, err := retryablehttp.NewRequest(http.MethodGet, dl.Url, nil)
 				if err != nil {
@@ -241,7 +243,16 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 				for key, value := range dl.ExtraHttpHeaders {
 					req.Header.Set(key, value)
 				}
-				req.Header.Set(traceHeader, trace)
+
+				// Inject OTEL trace context into outbound request.
+				otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(req.Header))
+
+				// Propagate correlation ID header.
+				if correlationIdHeader, ok := echoCtx.Get("correlationIdHeader").(string); ok {
+					if correlationId, ok := echoCtx.Get("correlationId").(string); ok {
+						req.Header.Set(correlationIdHeader, correlationId)
+					}
+				}
 
 				client := &retryablehttp.Client{
 					HTTPClient: &http.Client{
@@ -265,7 +276,7 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 				defer func() {
 					err := resp.Body.Close()
 					if err != nil {
-						logger.Error(fmt.Sprintf("close response body from '%s': %s", dl.Url, err))
+						logger.ErrorContext(ctx, fmt.Sprintf("close response body from '%s': %s", dl.Url, err))
 					}
 				}()
 
@@ -316,7 +327,7 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 				defer func() {
 					err := out.Close()
 					if err != nil {
-						logger.Error(fmt.Sprintf("close local file: %s", err))
+						logger.ErrorContext(ctx, fmt.Sprintf("close local file: %s", err))
 					}
 				}()
 
@@ -359,7 +370,7 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 		defer func() {
 			err := in.Close()
 			if err != nil {
-				logger.Error(fmt.Sprintf("close file header: %s", err))
+				logger.ErrorContext(context.Background(), fmt.Sprintf("close file header: %s", err))
 			}
 		}()
 
@@ -379,7 +390,7 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 		defer func() {
 			err := out.Close()
 			if err != nil {
-				logger.Error(fmt.Sprintf("close local file: %s", err))
+				logger.ErrorContext(context.Background(), fmt.Sprintf("close local file: %s", err))
 			}
 		}()
 
@@ -407,10 +418,10 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 		}
 	}
 
-	ctx.Log().Debug(fmt.Sprintf("form fields: %+v", ctx.values))
-	ctx.Log().Debug(fmt.Sprintf("form files: %+v", ctx.files))
-	ctx.Log().Debug(fmt.Sprintf("form files by field: %+v", ctx.filesByField))
-	ctx.Log().Debug(fmt.Sprintf("total bytes: %d", totalBytesRead.Load()))
+	ctx.Log().DebugContext(ctx, fmt.Sprintf("form fields: %+v", ctx.values))
+	ctx.Log().DebugContext(ctx, fmt.Sprintf("form files: %+v", ctx.files))
+	ctx.Log().DebugContext(ctx, fmt.Sprintf("form files by field: %+v", ctx.filesByField))
+	ctx.Log().DebugContext(ctx, fmt.Sprintf("total bytes: %d", totalBytesRead.Load()))
 
 	return ctx, cancel, err
 }
@@ -462,7 +473,7 @@ func (ctx *Context) CreateSubDirectory(dirName string) (string, error) {
 // Rename is just a wrapper around [os.Rename], as we need to mock this
 // behavior in our tests.
 func (ctx *Context) Rename(oldpath, newpath string) error {
-	ctx.Log().Debug(fmt.Sprintf("rename %s to %s", oldpath, newpath))
+	ctx.Log().DebugContext(ctx, fmt.Sprintf("rename %s to %s", oldpath, newpath))
 	err := ctx.pathRename.Rename(oldpath, newpath)
 	if err != nil {
 		return fmt.Errorf("rename path: %w", err)
@@ -488,8 +499,8 @@ func (ctx *Context) AddOutputPaths(paths ...string) error {
 	return nil
 }
 
-// Log returns the context [zap.Logger].
-func (ctx *Context) Log() *zap.Logger {
+// Log returns the context [slog.Logger].
+func (ctx *Context) Log() *slog.Logger {
 	return ctx.logger
 }
 
@@ -505,7 +516,7 @@ func (ctx *Context) BuildOutputFile() (string, error) {
 	}
 
 	if len(ctx.outputPaths) == 1 {
-		ctx.logger.Debug(fmt.Sprintf("only one output file '%s', skip archive creation", ctx.outputPaths[0]))
+		ctx.logger.DebugContext(ctx, fmt.Sprintf("only one output file '%s', skip archive creation", ctx.outputPaths[0]))
 		return ctx.outputPaths[0], nil
 	}
 
@@ -528,7 +539,7 @@ func (ctx *Context) BuildOutputFile() (string, error) {
 	defer func(out *os.File) {
 		err := out.Close()
 		if err != nil {
-			ctx.logger.Error(fmt.Sprintf("close zip file: %s", err))
+			ctx.logger.ErrorContext(ctx, fmt.Sprintf("close zip file: %s", err))
 		}
 	}(out)
 
@@ -537,7 +548,7 @@ func (ctx *Context) BuildOutputFile() (string, error) {
 		return "", fmt.Errorf("archive output files: %w", err)
 	}
 
-	ctx.logger.Debug(fmt.Sprintf("archive '%s' created", archivePath))
+	ctx.logger.DebugContext(ctx, fmt.Sprintf("archive '%s' created", archivePath))
 
 	return archivePath, nil
 }

pkg/modules/api/context_test.go

@@ -3,6 +3,7 @@ package api
 import (
 	"bytes"
 	"context"
+	"log/slog"
 	"mime/multipart"
 	"net/http"
 	"net/http/httptest"
@@ -10,7 +11,6 @@ import (
 	"time"
 
 	"github.com/labstack/echo/v4"
-	"go.uber.org/zap"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
@@ -35,14 +35,14 @@ func TestNewContext_Cancellation(t *testing.T) {
 	rec := httptest.NewRecorder()
 	c := e.NewContext(req, rec)
 
-	logger := zap.NewNop()
+	logger := slog.New(slog.DiscardHandler)
 	fs := gotenberg.NewFileSystem(new(gotenberg.OsMkdirAll))
 	timeout := time.Duration(10) * time.Second
 	downloadFromCfg := downloadFromConfig{
 		disable: true,
 	}
 
-	ctx, cancel, err := newContext(c, logger, fs, timeout, 0, downloadFromCfg, "trace", "trace")
+	ctx, cancel, err := newContext(c, logger, fs, timeout, 0, downloadFromCfg)
 	if err != nil {
 		t.Fatalf("expected no error from newContext, got: %v", err)
 	}

pkg/modules/api/middlewares.go

@@ -5,6 +5,7 @@ import (
 	"crypto/subtle"
 	"errors"
 	"fmt"
+	"log/slog"
 	"net/http"
 	"path/filepath"
 	"strings"
@@ -13,9 +14,13 @@ import (
 	"github.com/google/uuid"
 	"github.com/labstack/echo/v4"
 	"github.com/labstack/echo/v4/middleware"
-	"go.uber.org/zap"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/trace"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
+	semconvutil "github.com/gotenberg/gotenberg/v8/pkg/gotenberg/semconv"
 )
 
 var (
@@ -69,8 +74,7 @@ func ParseError(err error) (int, string) {
 		return http.StatusBadRequest, "At least one PDF engine cannot process the requested rotation angle, while others may have failed due to different issues"
 	}
 
-	var invalidArgsError *gotenberg.PdfEngineInvalidArgsError
-	if errors.As(err, &invalidArgsError) {
+	if invalidArgsError, ok := errors.AsType[*gotenberg.PdfEngineInvalidArgsError](err); ok {
 		return http.StatusBadRequest, invalidArgsError.Error()
 	}
 
@@ -87,14 +91,14 @@ func ParseError(err error) (int, string) {
 // returns a response as "text/plain; charset=UTF-8".
 func httpErrorHandler() echo.HTTPErrorHandler {
 	return func(err error, c echo.Context) {
-		logger := c.Get("logger").(*zap.Logger)
+		logger := c.Get("logger").(*slog.Logger)
 		status, message := ParseError(err)
 
 		c.Response().Header().Add(echo.HeaderContentType, echo.MIMETextPlainCharsetUTF8)
 
 		err = c.String(status, message)
 		if err != nil {
-			logger.Error(fmt.Sprintf("send error response: %s", err.Error()))
+			logger.ErrorContext(c.Request().Context(), fmt.Sprintf("send error response: %s", err.Error()))
 		}
 	}
 }
@@ -138,32 +142,6 @@ func rootPathMiddleware(rootPath string) echo.MiddlewareFunc {
 	}
 }
 
-// traceMiddleware sets the request identifier in the [echo.Context] under
-// "trace". Its value is either retrieved from the trace header or generated if
-// the header is not present / its value is empty.
-//
-//	trace := c.Get("trace").(string)
-//	traceHeader := c.Get("traceHeader").(string).
-func traceMiddleware(header string) echo.MiddlewareFunc {
-	return func(next echo.HandlerFunc) echo.HandlerFunc {
-		return func(c echo.Context) error {
-			// Get or create the request identifier.
-			trace := c.Request().Header.Get(header)
-
-			if trace == "" {
-				trace = uuid.New().String()
-			}
-
-			c.Set("trace", trace)
-			c.Set("traceHeader", header)
-			c.Response().Header().Add(header, trace)
-
-			// Call the next middleware in the chain.
-			return next(c)
-		}
-	}
-}
-
 // outputFilenameMiddleware sets the output filename in the [echo.Context]
 // under "outputFilename".
 //
@@ -183,59 +161,28 @@ func outputFilenameMiddleware() echo.MiddlewareFunc {
 	}
 }
 
-// loggerMiddleware sets the logger in the [echo.Context] under "logger" and
-// logs a synchronous request result.
+// telemetryMiddleware manages telemetry. It sets the correlation ID in the
+// [echo.Context] under "correlationId".
 //
-//	logger := c.Get("logger").(*zap.Logger)
-func loggerMiddleware(logger *zap.Logger, disableLoggingForPaths []string) echo.MiddlewareFunc {
+//	correlationIdHeader := c.Get("correlationIdHeader").(string)
+//	correlationId := c.Get("correlationId").(string)
+func telemetryMiddleware(logger *slog.Logger, serverName, correlationIdHeader string, disableTelemetryForPaths []string) echo.MiddlewareFunc {
+	meter := gotenberg.Meter()
+	semconvSrv := semconvutil.NewHTTPServer(meter)
+
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {
 			startTime := c.Get("startTime").(time.Time)
-			trace := c.Get("trace").(string)
 			rootPath := c.Get("rootPath").(string)
 
-			// Create the application logger and add it to our locals.
-			appLogger := logger.
-				With(zap.String("log_type", "application")).
-				With(zap.String("trace", trace))
+			request := c.Request()
+			savedCtx := request.Context()
+			defer func() {
+				request = request.WithContext(savedCtx)
+				c.SetRequest(request)
+			}()
 
-			c.Set("logger", appLogger.Named(func() string {
-				return strings.ReplaceAll(
-					strings.ReplaceAll(c.Request().URL.Path, rootPath, ""),
-					"/",
-					"",
-				)
-			}()))
-
-			// Call the next middleware in the chain.
-			err := next(c)
-			if err != nil {
-				c.Error(err)
-			}
-
-			// Create the access logger.
-			accessLogger := logger.
-				With(zap.String("log_type", "access")).
-				With(zap.String("trace", trace))
-
-			for _, path := range disableLoggingForPaths {
-				URI := fmt.Sprintf("%s%s", rootPath, path)
-
-				if c.Request().RequestURI == URI {
-					return nil
-				}
-			}
-
-			// Last piece for calculating the latency.
-			finishTime := time.Now()
-
-			// Now, let's log!
-			fields := make([]zap.Field, 12)
-			fields[0] = zap.String("remote_ip", c.RealIP())
-			fields[1] = zap.String("host", c.Request().Host)
-			fields[2] = zap.String("uri", c.Request().RequestURI)
-			fields[3] = zap.String("method", c.Request().Method)
-			fields[4] = zap.String("path", func() string {
+			routePath := func() string {
 				path := c.Request().URL.Path
 
 				if path == "" {
@@ -243,21 +190,127 @@ func loggerMiddleware(logger *zap.Logger, disableLoggingForPaths []string) echo.
 				}
 
 				return path
-			}())
-			fields[5] = zap.String("referer", c.Request().Referer())
-			fields[6] = zap.String("user_agent", c.Request().UserAgent())
-			fields[7] = zap.Int("status", c.Response().Status)
-			fields[8] = zap.Int64("latency", int64(finishTime.Sub(startTime)))
-			fields[9] = zap.String("latency_human", finishTime.Sub(startTime).String())
-			fields[10] = zap.Int64("bytes_in", c.Request().ContentLength)
-			fields[11] = zap.Int64("bytes_out", c.Response().Size)
+			}()
+
+			// Evaluate if we should skip telemetry for this path.
+			skipTelemetry := false
+			for _, path := range disableTelemetryForPaths {
+				URI := fmt.Sprintf("%s%s", rootPath, path)
+				if c.Request().RequestURI == URI {
+					skipTelemetry = true
+					break
+				}
+			}
+
+			if skipTelemetry {
+				c.Set("logger", slog.New(slog.DiscardHandler))
+
+				err := next(c)
+				if err != nil {
+					c.Error(err)
+				}
+				return nil
+			}
+
+			correlationId := request.Header.Get(correlationIdHeader)
+			if correlationId == "" {
+				correlationId = uuid.NewString()
+			}
+			c.Set("correlationIdHeader", correlationIdHeader)
+			c.Set("correlationId", correlationId)
+
+			ctx := otel.GetTextMapPropagator().Extract(savedCtx, propagation.HeaderCarrier(request.Header))
+
+			rAttr := semconvSrv.Route(routePath)
+			opts := []trace.SpanStartOption{
+				trace.WithAttributes(
+					semconvSrv.RequestTraceAttrs(serverName, request, semconvutil.RequestTraceAttrsOpts{})...,
+				),
+				trace.WithSpanKind(trace.SpanKindServer),
+				trace.WithAttributes(rAttr),
+			}
+			spanName := strings.ToUpper(c.Request().Method) + " " + routePath
+
+			tracer := gotenberg.Tracer()
+			ctx, span := tracer.Start(ctx, spanName, opts...)
+			defer span.End()
+
+			otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(c.Response().Header()))
+
+			c.Response().Header().Set(correlationIdHeader, correlationId)
+			c.SetRequest(c.Request().WithContext(ctx))
+
+			appLogger := logger.
+				With(slog.String("log_type", "application")).
+				With(slog.String("correlation_id", correlationId))
+
+			loggerName := strings.ReplaceAll(
+				strings.ReplaceAll(c.Request().URL.Path, rootPath, ""),
+				"/",
+				"",
+			)
+
+			c.Set("logger", appLogger.With(slog.String("logger", loggerName)))
+
+			// Call the next middleware in the chain.
+			err := next(c)
+			finishTime := time.Now()
+
+			status := c.Response().Status
+			if err != nil {
+				parsedStatus, _ := ParseError(err)
+				status = parsedStatus
+
+				span.SetAttributes(attribute.String("error", err.Error()))
+				c.Error(err)
+			}
+
+			span.SetStatus(semconvSrv.Status(status))
+			span.SetAttributes(semconvSrv.ResponseTraceAttrs(semconvutil.ResponseTelemetry{
+				StatusCode: status,
+				WriteBytes: c.Response().Size,
+			})...)
+
+			accessLogger := logger.
+				With(slog.String("log_type", "access")).
+				With(slog.String("correlation_id", correlationId)).
+				With(slog.String("remote_ip", c.RealIP())).
+				With(slog.String("host", c.Request().Host)).
+				With(slog.String("uri", c.Request().RequestURI)).
+				With(slog.String("method", c.Request().Method)).
+				With(slog.String("path", routePath)).
+				With(slog.String("referer", c.Request().Referer())).
+				With(slog.String("user_agent", c.Request().UserAgent())).
+				With(slog.Int("status", c.Response().Status)).
+				With(slog.Int64("latency", int64(finishTime.Sub(startTime)))).
+				With(slog.String("latency_human", finishTime.Sub(startTime).String())).
+				With(slog.Int64("bytes_in", c.Request().ContentLength)).
+				With(slog.Int64("bytes_out", c.Response().Size))
 
 			if err != nil {
-				accessLogger.Error(err.Error(), fields...)
+				accessLogger.ErrorContext(ctx, err.Error())
 			} else {
-				accessLogger.Info("request handled", fields...)
+				accessLogger.InfoContext(ctx, "request handled")
 			}
 
+			additionalAttributes := []attribute.KeyValue{
+				semconvSrv.Route(routePath),
+			}
+
+			semconvSrv.RecordMetrics(ctx, semconvutil.ServerMetricData{
+				ServerName:   serverName,
+				ResponseSize: c.Response().Size,
+				MetricAttributes: semconvutil.MetricAttributes{
+					Req:                  request,
+					StatusCode:           status,
+					AdditionalAttributes: additionalAttributes,
+				},
+				MetricData: semconvutil.MetricData{
+					RequestSize: request.ContentLength,
+					ElapsedTime: float64(time.Since(startTime)) / float64(time.Millisecond),
+				},
+			})
+
 			return nil
 		}
 	}
@@ -284,13 +337,11 @@ func basicAuthMiddleware(username, password string) echo.MiddlewareFunc {
 func contextMiddleware(fs *gotenberg.FileSystem, timeout time.Duration, bodyLimit int64, downloadFromCfg downloadFromConfig) echo.MiddlewareFunc {
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {
-			logger := c.Get("logger").(*zap.Logger)
-			traceHeader := c.Get("traceHeader").(string)
-			trace := c.Get("trace").(string)
+			logger := c.Get("logger").(*slog.Logger)
 
 			// We create a context with a timeout so that underlying processes are
 			// able to stop early and correctly handle a timeout scenario.
-			ctx, cancel, err := newContext(c, logger, fs, timeout, bodyLimit, downloadFromCfg, traceHeader, trace)
+			ctx, cancel, err := newContext(c, logger, fs, timeout, bodyLimit, downloadFromCfg)
 			if err != nil {
 				cancel()
 
@@ -344,7 +395,7 @@ func contextMiddleware(fs *gotenberg.FileSystem, timeout time.Duration, bodyLimi
 func hardTimeoutMiddleware(hardTimeout time.Duration) echo.MiddlewareFunc {
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {
-			logger := c.Get("logger").(*zap.Logger)
+			logger := c.Get("logger").(*slog.Logger)
 
 			// Define a hard timeout if the route handler fails to timeout as
 			// expected.
@@ -361,7 +412,7 @@ func hardTimeoutMiddleware(hardTimeout time.Duration) echo.MiddlewareFunc {
 				// This deferred function allows us to recover from such scenarios.
 				defer func() {
 					if r := recover(); r != nil {
-						logger.Debug(fmt.Sprintf("recovering from a panic (possible cause being a hard timeout): %s", r))
+						logger.DebugContext(hardTimeoutCtx, fmt.Sprintf("recovering from a panic (possible cause being a hard timeout): %s", r))
 					}
 				}()
 
@@ -373,7 +424,7 @@ func hardTimeoutMiddleware(hardTimeout time.Duration) echo.MiddlewareFunc {
 			case err := <-errChan:
 				return err
 			case <-hardTimeoutCtx.Done():
-				logger.Debug("hard timeout as the route handler did not timeout as expected")
+				logger.DebugContext(hardTimeoutCtx, "hard timeout as the route handler did not timeout as expected")
 
 				return fmt.Errorf("hard timeout: %w", hardTimeoutCtx.Err())
 			}

pkg/modules/api/mocks.go

@@ -1,9 +1,10 @@
 package api
 
 import (
+	"log/slog"
+
 	"github.com/alexliesenfeld/health"
 	"github.com/labstack/echo/v4"
-	"go.uber.org/zap"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
@@ -73,8 +74,8 @@ func (ctx *ContextMock) OutputPaths() []string {
 // SetLogger sets the logger.
 //
 //	ctx := &api.ContextMock{Context: &api.Context{}}
-//	ctx.SetLogger(zap.NewNop())
-func (ctx *ContextMock) SetLogger(logger *zap.Logger) {
+//	ctx.SetLogger(slog.Default())
+func (ctx *ContextMock) SetLogger(logger *slog.Logger) {
 	ctx.logger = logger
 }
 

pkg/modules/chromium/browser.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"strings"
 	"sync"
@@ -18,15 +19,14 @@ import (
 	"github.com/chromedp/chromedp"
 	"github.com/dlclark/regexp2"
 	"github.com/shirou/gopsutil/v4/process"
-	"go.uber.org/zap"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
 type browser interface {
 	gotenberg.Process
-	pdf(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error
-	screenshot(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error
+	pdf(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error
+	screenshot(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error
 }
 
 type browserArguments struct {
@@ -72,7 +72,7 @@ func newChromiumBrowser(arguments browserArguments) browser {
 	return b
 }
 
-func (b *chromiumBrowser) Start(logger *zap.Logger) error {
+func (b *chromiumBrowser) Start(logger *slog.Logger) error {
 	if b.isStarted.Load() {
 		return errors.New("browser is already started")
 	}
@@ -164,7 +164,7 @@ func (b *chromiumBrowser) Start(logger *zap.Logger) error {
 	return nil
 }
 
-func (b *chromiumBrowser) Stop(logger *zap.Logger) error {
+func (b *chromiumBrowser) Stop(logger *slog.Logger) error {
 	if !b.isStarted.Load() {
 		// No big deal? Like calling cancel twice.
 		return nil
@@ -181,7 +181,7 @@ func (b *chromiumBrowser) Stop(logger *zap.Logger) error {
 		// Clean up stuck processes.
 		ps, err := process.Processes()
 		if err != nil {
-			logger.Error(fmt.Sprintf("list processes: %v", err))
+			logger.ErrorContext(context.Background(), fmt.Sprintf("list processes: %v", err))
 		} else {
 			for _, p := range ps {
 				func() {
@@ -199,9 +199,9 @@ func (b *chromiumBrowser) Stop(logger *zap.Logger) error {
 
 					err = p.KillWithContext(killCtx)
 					if err != nil {
-						logger.Error(fmt.Sprintf("kill process: %v", err))
+						logger.ErrorContext(context.Background(), fmt.Sprintf("kill process: %v", err))
 					} else {
-						logger.Debug(fmt.Sprintf("Chromium process %d killed", p.Pid))
+						logger.DebugContext(context.Background(), fmt.Sprintf("Chromium process %d killed", p.Pid))
 					}
 				}()
 			}
@@ -215,15 +215,15 @@ func (b *chromiumBrowser) Stop(logger *zap.Logger) error {
 
 			err = os.RemoveAll(userProfileDirPath)
 			if err != nil {
-				logger.Error(fmt.Sprintf("remove Chromium's user profile directory: %s", err))
+				logger.ErrorContext(context.Background(), fmt.Sprintf("remove Chromium's user profile directory: %s", err))
 			} else {
-				logger.Debug(fmt.Sprintf("'%s' Chromium's user profile directory removed", userProfileDirPath))
+				logger.DebugContext(context.Background(), fmt.Sprintf("'%s' Chromium's user profile directory removed", userProfileDirPath))
 			}
 
 			// Also, remove Chromium-specific files in the temporary directory.
-			err = gotenberg.GarbageCollect(logger, os.TempDir(), []string{".org.chromium.Chromium", ".com.google.Chrome"}, expirationTime)
+			err = gotenberg.GarbageCollect(context.Background(), logger, os.TempDir(), []string{".org.chromium.Chromium", ".com.google.Chrome"}, expirationTime)
 			if err != nil {
-				logger.Error(err.Error())
+				logger.ErrorContext(context.Background(), err.Error())
 			}
 		}()
 	}(copyUserProfileDirPath, expirationTime)
@@ -239,7 +239,7 @@ func (b *chromiumBrowser) Stop(logger *zap.Logger) error {
 	return nil
 }
 
-func (b *chromiumBrowser) Healthy(logger *zap.Logger) bool {
+func (b *chromiumBrowser) Healthy(logger *slog.Logger) bool {
 	// Good to know: the supervisor does not call this method if no first start
 	// or if the process is restarting.
 
@@ -266,14 +266,14 @@ func (b *chromiumBrowser) Healthy(logger *zap.Logger) bool {
 		return err
 	}))
 	if err != nil {
-		logger.Error(fmt.Sprintf("browser health check failed: %s", err))
+		logger.ErrorContext(context.Background(), fmt.Sprintf("browser health check failed: %s", err))
 		return false
 	}
 
 	return true
 }
 
-func (b *chromiumBrowser) pdf(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
+func (b *chromiumBrowser) pdf(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error {
 	// Note: no error wrapping because it leaks on errors we want to display to
 	// the end user.
 	return b.do(ctx, logger, url, options.Options, chromedp.Tasks{
@@ -299,7 +299,7 @@ func (b *chromiumBrowser) pdf(ctx context.Context, logger *zap.Logger, url, outp
 	})
 }
 
-func (b *chromiumBrowser) screenshot(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error {
+func (b *chromiumBrowser) screenshot(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error {
 	// Note: no error wrapping because it leaks on errors we want to display to
 	// the end user.
 	return b.do(ctx, logger, url, options.Options, chromedp.Tasks{
@@ -326,7 +326,7 @@ func (b *chromiumBrowser) screenshot(ctx context.Context, logger *zap.Logger, ur
 	})
 }
 
-func (b *chromiumBrowser) do(ctx context.Context, logger *zap.Logger, url string, options Options, tasks chromedp.Tasks) error {
+func (b *chromiumBrowser) do(ctx context.Context, logger *slog.Logger, url string, options Options, tasks chromedp.Tasks) error {
 	if !b.isStarted.Load() {
 		return errors.New("browser not started, cannot handle tasks")
 	}

pkg/modules/chromium/chromium.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/exec"
 	"strings"
@@ -14,7 +15,8 @@ import (
 	"github.com/chromedp/cdproto/network"
 	"github.com/dlclark/regexp2"
 	flag "github.com/spf13/pflag"
-	"go.uber.org/zap"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 	"github.com/gotenberg/gotenberg/v8/pkg/modules/api"
@@ -91,10 +93,17 @@ type Chromium struct {
 	maxConcurrency int64
 	args           browserArguments
 
-	logger     *zap.Logger
+	logger     *slog.Logger
 	browser    browser
 	supervisor gotenberg.ProcessSupervisor
 	engine     gotenberg.PdfEngine
+
+	reqsCounter               metric.Int64Counter
+	errsCounter               metric.Int64Counter
+	conversionDurationCounter metric.Float64Histogram
+	queueWaitDurationCounter  metric.Float64Histogram
+	pdfOutputSizeCounter      metric.Int64Histogram
+	imageOutputSizeCounter    metric.Int64Histogram
 }
 
 // Options are the common options for all conversions.
@@ -400,8 +409,8 @@ type ExtraHttpHeader struct {
 
 // Api helps to interact with Chromium for converting HTML documents to PDF.
 type Api interface {
-	Pdf(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error
-	Screenshot(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error
+	Pdf(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error
+	Screenshot(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error
 }
 
 // Provider is a module interface that exposes a method for creating an [Api]
@@ -488,15 +497,7 @@ func (mod *Chromium) Provision(ctx *gotenberg.Context) error {
 	}
 
 	// Logger.
-	loggerProvider, err := ctx.Module(new(gotenberg.LoggerProvider))
-	if err != nil {
-		return fmt.Errorf("get logger provider: %w", err)
-	}
-	logger, err := loggerProvider.(gotenberg.LoggerProvider).Logger(mod)
-	if err != nil {
-		return fmt.Errorf("get logger: %w", err)
-	}
-	mod.logger = logger.Named("browser")
+	mod.logger = gotenberg.Logger(mod).With(slog.String("logger", "browser"))
 
 	// Process.
 	mod.browser = newChromiumBrowser(mod.args)
@@ -513,6 +514,109 @@ func (mod *Chromium) Provision(ctx *gotenberg.Context) error {
 	}
 	mod.engine = engine
 
+	// Metrics.
+	meter := gotenberg.Meter()
+
+	// Observable gauges.
+	_, err = meter.Int64ObservableGauge(
+		"chromium.requests.active",
+		metric.WithDescription("Current number of active Chromium requests"),
+		metric.WithUnit("{request}"),
+		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
+			o.Observe(mod.supervisor.ActiveTasksCount())
+			return nil
+		}),
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.requests.active gauge: %w", err)
+	}
+
+	_, err = meter.Int64ObservableGauge(
+		"chromium.requests.queue_size",
+		metric.WithDescription("Current number of Chromium conversion requests waiting to be treated"),
+		metric.WithUnit("{request}"),
+		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
+			o.Observe(mod.supervisor.ReqQueueSize())
+			return nil
+		}),
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.requests.queue_size gauge: %w", err)
+	}
+
+	_, err = meter.Int64ObservableCounter(
+		"chromium.process.restarts.total",
+		metric.WithDescription("Current number of Chromium restarts"),
+		metric.WithUnit("{restart}"),
+		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
+			o.Observe(mod.supervisor.RestartsCount())
+			return nil
+		}),
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.process.restarts.total counter: %w", err)
+	}
+
+	// Counters.
+	mod.reqsCounter, err = meter.Int64Counter(
+		"chromium.requests.total",
+		metric.WithDescription("Total number of Chromium conversion requests"),
+		metric.WithUnit("{request}"),
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.requests.total counter: %w", err)
+	}
+
+	mod.errsCounter, err = meter.Int64Counter(
+		"chromium.errors.total",
+		metric.WithDescription("Total number of Chromium conversion errors"),
+		metric.WithUnit("{error}"),
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.errors.total counter: %w", err)
+	}
+
+	// Histograms.
+	durationBuckets := metric.WithExplicitBucketBoundaries(0.5, 1, 2, 5, 10, 30, 60)
+
+	mod.conversionDurationCounter, err = meter.Float64Histogram(
+		"chromium.conversion.duration",
+		metric.WithDescription("Duration of Chromium conversions"),
+		metric.WithUnit("s"),
+		durationBuckets,
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.conversion.duration histogram: %w", err)
+	}
+
+	mod.queueWaitDurationCounter, err = meter.Float64Histogram(
+		"chromium.queue.wait.duration",
+		metric.WithDescription("Duration of waiting in queue for Chromium conversions"),
+		metric.WithUnit("s"),
+		durationBuckets,
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.queue.wait.duration histogram: %w", err)
+	}
+
+	mod.pdfOutputSizeCounter, err = meter.Int64Histogram(
+		"chromium.pdf.output.size",
+		metric.WithDescription("Size of PDF output from Chromium conversions"),
+		metric.WithUnit("By"),
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.pdf.output.size histogram: %w", err)
+	}
+
+	mod.imageOutputSizeCounter, err = meter.Int64Histogram(
+		"chromium.image.output.size",
+		metric.WithDescription("Size of image output from Chromium screenshots"),
+		metric.WithUnit("By"),
+	)
+	if err != nil {
+		return fmt.Errorf("create chromium.image.output.size histogram: %w", err)
+	}
+
 	return nil
 }
 
@@ -563,7 +667,7 @@ func (mod *Chromium) StartupMessage() string {
 func (mod *Chromium) Stop(ctx context.Context) error {
 	// Block until the context is done so that another module may gracefully
 	// stop before we do a shutdown.
-	mod.logger.Debug("wait for the end of grace duration")
+	mod.logger.DebugContext(ctx, "wait for the end of grace duration")
 
 	<-ctx.Done()
 
@@ -679,20 +783,138 @@ func (mod *Chromium) Routes() ([]api.Route, error) {
 }
 
 // Pdf converts a URL to PDF.
-func (mod *Chromium) Pdf(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
-	// Note: no error wrapping because it leaks on errors we want to display to
-	// the end user.
-	return mod.supervisor.Run(ctx, logger, func() error {
+func (mod *Chromium) Pdf(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error {
+	start := time.Now()
+	var conversionStart time.Time
+
+	err := mod.supervisor.Run(ctx, logger, func() error {
+		conversionStart = time.Now()
 		return mod.browser.pdf(ctx, logger, url, outputPath, options)
 	})
+
+	end := time.Now()
+
+	status := "success"
+	if err != nil {
+		if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
+			status = "timeout"
+		} else {
+			status = "error"
+		}
+
+		reason := "unknown"
+		switch {
+		case errors.Is(err, context.DeadlineExceeded):
+			reason = "timeout"
+		case errors.Is(err, context.Canceled):
+			reason = "context_cancelled"
+		case errors.Is(err, ErrInvalidHttpStatusCode) || errors.Is(err, ErrInvalidResourceHttpStatusCode) || errors.Is(err, ErrLoadingFailed) || errors.Is(err, ErrResourceLoadingFailed) || errors.Is(err, ErrInvalidEvaluationExpression) || errors.Is(err, ErrInvalidSelectorQuery):
+			reason = "invalid_input"
+		case errors.Is(err, gotenberg.ErrMaximumQueueSizeExceeded) || errors.Is(err, gotenberg.ErrProcessAlreadyRestarting):
+			reason = "chromium_unavailable"
+		}
+
+		mod.errsCounter.Add(ctx, 1, metric.WithAttributes(
+			attribute.String("reason", reason),
+		))
+	}
+
+	if !conversionStart.IsZero() {
+		waitDuration := conversionStart.Sub(start).Seconds()
+		conversionDuration := end.Sub(conversionStart).Seconds()
+
+		mod.queueWaitDurationCounter.Record(ctx, waitDuration, metric.WithAttributes(
+			attribute.String("status", status),
+		))
+		mod.conversionDurationCounter.Record(ctx, conversionDuration, metric.WithAttributes(
+			attribute.String("status", status),
+		))
+	} else {
+		waitDuration := end.Sub(start).Seconds()
+		mod.queueWaitDurationCounter.Record(ctx, waitDuration, metric.WithAttributes(
+			attribute.String("status", status),
+		))
+	}
+
+	mod.reqsCounter.Add(ctx, 1, metric.WithAttributes(
+		attribute.String("status", status),
+	))
+
+	if err == nil {
+		if fileInfo, statErr := os.Stat(outputPath); statErr == nil {
+			mod.pdfOutputSizeCounter.Record(ctx, fileInfo.Size())
+		}
+	}
+
+	return err
 }
 
-func (mod *Chromium) Screenshot(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error {
-	// Note: no error wrapping because it leaks on errors we want to display to
-	// the end user.
-	return mod.supervisor.Run(ctx, logger, func() error {
+func (mod *Chromium) Screenshot(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error {
+	start := time.Now()
+	var conversionStart time.Time
+
+	err := mod.supervisor.Run(ctx, logger, func() error {
+		conversionStart = time.Now()
 		return mod.browser.screenshot(ctx, logger, url, outputPath, options)
 	})
+
+	end := time.Now()
+
+	status := "success"
+	if err != nil {
+		if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
+			status = "timeout"
+		} else {
+			status = "error"
+		}
+
+		reason := "unknown"
+		switch {
+		case errors.Is(err, context.DeadlineExceeded):
+			reason = "timeout"
+		case errors.Is(err, context.Canceled):
+			reason = "context_cancelled"
+		case errors.Is(err, ErrInvalidHttpStatusCode) || errors.Is(err, ErrInvalidResourceHttpStatusCode) || errors.Is(err, ErrLoadingFailed) || errors.Is(err, ErrResourceLoadingFailed) || errors.Is(err, ErrInvalidEvaluationExpression) || errors.Is(err, ErrInvalidSelectorQuery):
+			reason = "invalid_input"
+		case errors.Is(err, gotenberg.ErrMaximumQueueSizeExceeded):
+			reason = "chromium_maximum_queue_size_exceeded"
+		case errors.Is(err, gotenberg.ErrProcessAlreadyRestarting):
+			reason = "chromium_unavailable"
+		}
+
+		mod.errsCounter.Add(ctx, 1, metric.WithAttributes(
+			attribute.String("reason", reason),
+		))
+	}
+
+	if !conversionStart.IsZero() {
+		waitDuration := conversionStart.Sub(start).Seconds()
+		conversionDuration := end.Sub(conversionStart).Seconds()
+
+		mod.queueWaitDurationCounter.Record(ctx, waitDuration, metric.WithAttributes(
+			attribute.String("status", status),
+		))
+		mod.conversionDurationCounter.Record(ctx, conversionDuration, metric.WithAttributes(
+			attribute.String("status", status),
+		))
+	} else {
+		waitDuration := end.Sub(start).Seconds()
+		mod.queueWaitDurationCounter.Record(ctx, waitDuration, metric.WithAttributes(
+			attribute.String("status", status),
+		))
+	}
+
+	mod.reqsCounter.Add(ctx, 1, metric.WithAttributes(
+		attribute.String("status", status),
+	))
+
+	if err == nil {
+		if fileInfo, statErr := os.Stat(outputPath); statErr == nil {
+			mod.imageOutputSizeCounter.Record(ctx, fileInfo.Size())
+		}
+	}
+
+	return err
 }
 
 // Interface guards.

pkg/modules/chromium/debug.go

@@ -1,28 +1,28 @@
 package chromium
 
 import (
+	"context"
 	"fmt"
 	"io"
-
-	"go.uber.org/zap"
+	"log/slog"
 )
 
-// debugLogger is wrapper around a [zap.Logger] which is used for debugging
+// debugLogger is wrapper around a [slog.Logger] which is used for debugging
 // Chromium.
 type debugLogger struct {
-	logger *zap.Logger
+	logger *slog.Logger
 }
 
 // Write logs the bytes in a debug message.
 func (debug *debugLogger) Write(p []byte) (n int, err error) {
-	debug.logger.Debug(string(p))
+	debug.logger.DebugContext(context.Background(), string(p))
 
 	return len(p), nil
 }
 
 // Printf logs a debug message.
 func (debug *debugLogger) Printf(format string, v ...any) {
-	debug.logger.Debug(fmt.Sprintf(format, v...))
+	debug.logger.DebugContext(context.Background(), fmt.Sprintf(format, v...))
 }
 
 // Interface guards.

pkg/modules/chromium/events.go

@@ -3,6 +3,7 @@ package chromium
 import (
 	"context"
 	"fmt"
+	"log/slog"
 	"net/http"
 	"net/url"
 	"slices"
@@ -17,7 +18,6 @@ import (
 	"github.com/chromedp/chromedp"
 	"github.com/dlclark/regexp2"
 	"go.uber.org/multierr"
-	"go.uber.org/zap"
 	"golang.org/x/sync/errgroup"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
@@ -33,29 +33,28 @@ type eventRequestPausedOptions struct {
 // allowed or not.  It also set the extra HTTP headers, if any.
 // See https://github.com/gotenberg/gotenberg/issues/1011.
 // TODO: https://chromedevtools.github.io/devtools-protocol/tot/Network/#method-setBlockedURLs (experimental for now).
-func listenForEventRequestPaused(ctx context.Context, logger *zap.Logger, options eventRequestPausedOptions) {
+func listenForEventRequestPaused(ctx context.Context, logger *slog.Logger, options eventRequestPausedOptions) {
 	if len(options.extraHttpHeaders) == 0 {
-		logger.Debug("no extra HTTP headers")
+		logger.DebugContext(ctx, "no extra HTTP headers")
 	} else {
-		logger.Debug(fmt.Sprintf("extra HTTP headers: %+v", options.extraHttpHeaders))
+		logger.DebugContext(ctx, fmt.Sprintf("extra HTTP headers: %+v", options.extraHttpHeaders))
 	}
 
 	chromedp.ListenTarget(ctx, func(ev any) {
-		switch e := ev.(type) {
-		case *fetch.EventRequestPaused:
+		if e, ok := ev.(*fetch.EventRequestPaused); ok {
 			go func() {
-				logger.Debug(fmt.Sprintf("event EventRequestPaused fired for '%s'", e.Request.URL))
+				logger.DebugContext(ctx, fmt.Sprintf("event EventRequestPaused fired for '%s'", e.Request.URL))
 				allow := true
 
 				deadline, ok := ctx.Deadline()
 				if !ok {
-					logger.Error("context has no deadline, cannot filter URL")
+					logger.ErrorContext(ctx, "context has no deadline, cannot filter URL")
 					return
 				}
 
 				err := gotenberg.FilterDeadline(options.allowList, options.denyList, e.Request.URL, deadline)
 				if err != nil {
-					logger.Warn(err.Error())
+					logger.WarnContext(ctx, err.Error())
 					allow = false
 				}
 
@@ -73,7 +72,7 @@ func listenForEventRequestPaused(ctx context.Context, logger *zap.Logger, option
 					}
 
 					if !prefixMatch {
-						logger.Warn(fmt.Sprintf("'%s' is not within any allowed file prefix", e.Request.URL))
+						logger.WarnContext(ctx, fmt.Sprintf("'%s' is not within any allowed file prefix", e.Request.URL))
 						allow = false
 					}
 				}
@@ -85,7 +84,7 @@ func listenForEventRequestPaused(ctx context.Context, logger *zap.Logger, option
 					req := fetch.FailRequest(e.RequestID, network.ErrorReasonAccessDenied)
 					err = req.Do(executorCtx)
 					if err != nil {
-						logger.Error(fmt.Sprintf("fail request: %s", err))
+						logger.ErrorContext(ctx, fmt.Sprintf("fail request: %s", err))
 					}
 					return
 				}
@@ -101,25 +100,26 @@ func listenForEventRequestPaused(ctx context.Context, logger *zap.Logger, option
 					for _, header := range options.extraHttpHeaders {
 						if header.Scope == nil {
 							// Non-scoped header.
-							logger.Debug(fmt.Sprintf("extra HTTP header '%s' will be set for request URL '%s'", header.Name, e.Request.URL))
+							logger.DebugContext(ctx, fmt.Sprintf("extra HTTP header '%s' will be set for request URL '%s'", header.Name, e.Request.URL))
 							extraHttpHeadersToSet = append(extraHttpHeadersToSet, header)
 							continue
 						}
 
 						ok, err := header.Scope.MatchString(e.Request.URL)
-						if err != nil {
-							logger.Error(fmt.Sprintf("fail to match extra HTTP header '%s' scope with URL '%s': %s", header.Name, e.Request.URL, err))
-						} else if ok {
-							logger.Debug(fmt.Sprintf("extra HTTP header '%s' (scoped) will be set for request URL '%s'", header.Name, e.Request.URL))
+						switch {
+						case err != nil:
+							logger.ErrorContext(ctx, fmt.Sprintf("fail to match extra HTTP header '%s' scope with URL '%s': %s", header.Name, e.Request.URL, err))
+						case ok:
+							logger.DebugContext(ctx, fmt.Sprintf("extra HTTP header '%s' (scoped) will be set for request URL '%s'", header.Name, e.Request.URL))
 							extraHttpHeadersToSet = append(extraHttpHeadersToSet, header)
-						} else {
-							logger.Debug(fmt.Sprintf("scoped extra HTTP header '%s' (scoped) will not be set for request URL '%s'", header.Name, e.Request.URL))
+						default:
+							logger.DebugContext(ctx, fmt.Sprintf("scoped extra HTTP header '%s' (scoped) will not be set for request URL '%s'", header.Name, e.Request.URL))
 						}
 					}
 				}
 
 				if len(extraHttpHeadersToSet) > 0 {
-					logger.Debug(fmt.Sprintf("setting extra HTTP headers for request URL '%s': %+v", e.Request.URL, extraHttpHeadersToSet))
+					logger.DebugContext(ctx, fmt.Sprintf("setting extra HTTP headers for request URL '%s': %+v", e.Request.URL, extraHttpHeadersToSet))
 
 					originalHeaders := e.Request.Headers
 					headers := make(map[string]string)
@@ -129,7 +129,7 @@ func listenForEventRequestPaused(ctx context.Context, logger *zap.Logger, option
 						if ok {
 							headers[key] = strValue
 						} else {
-							logger.Error(fmt.Sprintf("ignoring header '%s' for URL '%s' since it cannot be cast to a string", key, e.Request.URL))
+							logger.ErrorContext(ctx, fmt.Sprintf("ignoring header '%s' for URL '%s' since it cannot be cast to a string", key, e.Request.URL))
 						}
 					}
 
@@ -152,7 +152,7 @@ func listenForEventRequestPaused(ctx context.Context, logger *zap.Logger, option
 
 				err = req.Do(executorCtx)
 				if err != nil {
-					logger.Error(fmt.Sprintf("continue request: %s", err))
+					logger.ErrorContext(ctx, fmt.Sprintf("continue request: %s", err))
 				}
 			}()
 		}
@@ -177,7 +177,7 @@ type eventResponseReceivedOptions struct {
 // https://github.com/gotenberg/gotenberg/issues/1021.
 func listenForEventResponseReceived(
 	ctx context.Context,
-	logger *zap.Logger,
+	logger *slog.Logger,
 	options eventResponseReceivedOptions,
 ) {
 	normalizedIgnoreDomains := normalizeDomains(options.ignoreResourceHttpStatusDomains)
@@ -197,10 +197,9 @@ func listenForEventResponseReceived(
 	}
 
 	chromedp.ListenTarget(ctx, func(ev any) {
-		switch ev := ev.(type) {
-		case *network.EventResponseReceived:
+		if ev, ok := ev.(*network.EventResponseReceived); ok {
 			if ev.Response.URL == options.mainPageUrl {
-				logger.Debug(fmt.Sprintf("event EventResponseReceived fired for main page: %+v", ev.Response))
+				logger.DebugContext(ctx, fmt.Sprintf("event EventResponseReceived fired for main page: %+v", ev.Response))
 
 				if slices.Contains(options.failOnHttpStatusCodes, ev.Response.Status) {
 					options.invalidHttpStatusCodeMu.Lock()
@@ -212,11 +211,11 @@ func listenForEventResponseReceived(
 				return
 			}
 
-			logger.Debug(fmt.Sprintf("event EventResponseReceived fired for a resource: %+v", ev.Response))
+			logger.DebugContext(ctx, fmt.Sprintf("event EventResponseReceived fired for a resource: %+v", ev.Response))
 
 			if slices.Contains(options.failOnResourceOnHttpStatusCode, ev.Response.Status) {
 				if !shouldCheckResourceHttpStatusCode(ev.Response.URL, normalizedIgnoreDomains) {
-					logger.Debug(fmt.Sprintf("skip resource HTTP status code check for '%s' due to domain filtering", ev.Response.URL))
+					logger.DebugContext(ctx, fmt.Sprintf("skip resource HTTP status code check for '%s' due to domain filtering", ev.Response.URL))
 					return
 				}
 
@@ -318,11 +317,10 @@ type eventLoadingFailedOptions struct {
 // https://github.com/gotenberg/gotenberg/issues/913.
 // https://github.com/gotenberg/gotenberg/issues/959.
 // https://github.com/gotenberg/gotenberg/issues/1021.
-func listenForEventLoadingFailed(ctx context.Context, logger *zap.Logger, options eventLoadingFailedOptions) {
+func listenForEventLoadingFailed(ctx context.Context, logger *slog.Logger, options eventLoadingFailedOptions) {
 	chromedp.ListenTarget(ctx, func(ev any) {
-		switch ev := ev.(type) {
-		case *network.EventLoadingFailed:
-			logger.Debug(fmt.Sprintf("event EventLoadingFailed fired: %+v", ev.ErrorText))
+		if ev, ok := ev.(*network.EventLoadingFailed); ok {
+			logger.DebugContext(ctx, fmt.Sprintf("event EventLoadingFailed fired: %+v", ev.ErrorText))
 
 			// We are looking for common errors.
 			// TODO: sufficient?
@@ -341,14 +339,14 @@ func listenForEventLoadingFailed(ctx context.Context, logger *zap.Logger, option
 				"net::ERR_HTTP2_PROTOCOL_ERROR",
 			}
 			if !slices.Contains(errors, ev.ErrorText) {
-				logger.Debug(fmt.Sprintf("skip EventLoadingFailed: '%s' is not part of %+v", ev.ErrorText, errors))
+				logger.DebugContext(ctx, fmt.Sprintf("skip EventLoadingFailed: '%s' is not part of %+v", ev.ErrorText, errors))
 				return
 			}
 
 			if ev.Type == network.ResourceTypeDocument {
 				// Supposition: except iframe, an event loading failed with a
 				// resource type Document is about the main page.
-				logger.Debug("event EventLoadingFailed fired for main page")
+				logger.DebugContext(ctx, "event EventLoadingFailed fired for main page")
 
 				options.loadingFailedMu.Lock()
 				defer options.loadingFailedMu.Unlock()
@@ -358,7 +356,7 @@ func listenForEventLoadingFailed(ctx context.Context, logger *zap.Logger, option
 				return
 			}
 
-			logger.Debug("event EventLoadingFailed fired for a resource")
+			logger.DebugContext(ctx, "event EventLoadingFailed fired for a resource")
 
 			options.resourceLoadingFailedMu.Lock()
 			defer options.resourceLoadingFailedMu.Unlock()
@@ -374,11 +372,10 @@ func listenForEventLoadingFailed(ctx context.Context, logger *zap.Logger, option
 // listenForEventExceptionThrown listens for exceptions in the console and
 // appends those exceptions to the given error pointer.
 // See https://github.com/gotenberg/gotenberg/issues/262.
-func listenForEventExceptionThrown(ctx context.Context, logger *zap.Logger, consoleExceptions *error, consoleExceptionsMu *sync.RWMutex) {
+func listenForEventExceptionThrown(ctx context.Context, logger *slog.Logger, consoleExceptions *error, consoleExceptionsMu *sync.RWMutex) {
 	chromedp.ListenTarget(ctx, func(ev any) {
-		switch ev := ev.(type) {
-		case *runtime.EventExceptionThrown:
-			logger.Debug(fmt.Sprintf("event EventExceptionThrown fired: %+v", ev.ExceptionDetails))
+		if ev, ok := ev.(*runtime.EventExceptionThrown); ok {
+			logger.DebugContext(ctx, fmt.Sprintf("event EventExceptionThrown fired: %+v", ev.ExceptionDetails))
 
 			consoleExceptionsMu.Lock()
 			defer consoleExceptionsMu.Unlock()
@@ -390,13 +387,12 @@ func listenForEventExceptionThrown(ctx context.Context, logger *zap.Logger, cons
 
 // waitForEventDomContentEventFired waits until the event DomContentEventFired
 // is fired or the context timeout.
-func waitForEventDomContentEventFired(ctx context.Context, logger *zap.Logger) func() error {
+func waitForEventDomContentEventFired(ctx context.Context, logger *slog.Logger) func() error {
 	return func() error {
 		ch := make(chan struct{})
 		cctx, cancel := context.WithCancel(ctx)
 		chromedp.ListenTarget(cctx, func(ev any) {
-			switch ev.(type) {
-			case *page.EventDomContentEventFired:
+			if _, ok := ev.(*page.EventDomContentEventFired); ok {
 				cancel()
 				close(ch)
 			}
@@ -404,7 +400,7 @@ func waitForEventDomContentEventFired(ctx context.Context, logger *zap.Logger) f
 
 		select {
 		case <-ch:
-			logger.Debug("event DomContentEventFired fired")
+			logger.DebugContext(ctx, "event DomContentEventFired fired")
 			return nil
 		case <-ctx.Done():
 			return fmt.Errorf("wait for event DomContentEventFired: %w", ctx.Err())
@@ -414,13 +410,12 @@ func waitForEventDomContentEventFired(ctx context.Context, logger *zap.Logger) f
 
 // waitForEventLoadEventFired waits until the event LoadEventFired is fired or
 // the context timeout.
-func waitForEventLoadEventFired(ctx context.Context, logger *zap.Logger) func() error {
+func waitForEventLoadEventFired(ctx context.Context, logger *slog.Logger) func() error {
 	return func() error {
 		ch := make(chan struct{})
 		cctx, cancel := context.WithCancel(ctx)
 		chromedp.ListenTarget(cctx, func(ev any) {
-			switch ev.(type) {
-			case *page.EventLoadEventFired:
+			if _, ok := ev.(*page.EventLoadEventFired); ok {
 				cancel()
 				close(ch)
 			}
@@ -428,7 +423,7 @@ func waitForEventLoadEventFired(ctx context.Context, logger *zap.Logger) func()
 
 		select {
 		case <-ch:
-			logger.Debug("event LoadEventFired fired")
+			logger.DebugContext(ctx, "event LoadEventFired fired")
 			return nil
 		case <-ctx.Done():
 			return fmt.Errorf("wait for event LoadEventFired: %w", ctx.Err())
@@ -438,23 +433,20 @@ func waitForEventLoadEventFired(ctx context.Context, logger *zap.Logger) func()
 
 // waitForEventNetworkIdle waits until the event networkIdle is fired or the
 // context timeout.
-func waitForEventNetworkIdle(ctx context.Context, logger *zap.Logger) func() error {
+func waitForEventNetworkIdle(ctx context.Context, logger *slog.Logger) func() error {
 	return func() error {
 		ch := make(chan struct{})
 		cctx, cancel := context.WithCancel(ctx)
 		chromedp.ListenTarget(cctx, func(ev any) {
-			switch e := ev.(type) {
-			case *page.EventLifecycleEvent:
-				if e.Name == "networkIdle" {
-					cancel()
-					close(ch)
-				}
+			if e, ok := ev.(*page.EventLifecycleEvent); ok && e.Name == "networkIdle" {
+				cancel()
+				close(ch)
 			}
 		})
 
 		select {
 		case <-ch:
-			logger.Debug("event networkIdle fired")
+			logger.DebugContext(ctx, "event networkIdle fired")
 			return nil
 		case <-ctx.Done():
 			return fmt.Errorf("wait for event networkIdle: %w", ctx.Err())
@@ -469,12 +461,9 @@ func waitForEventNetworkAlmostIdle(ctx context.Context, logger *slog.Logger) fun
 		ch := make(chan struct{})
 		cctx, cancel := context.WithCancel(ctx)
 		chromedp.ListenTarget(cctx, func(ev any) {
-			switch e := ev.(type) {
-			case *page.EventLifecycleEvent:
-				if e.Name == "networkIdle2" {
-					cancel()
-					close(ch)
-				}
+			if e, ok := ev.(*page.EventLifecycleEvent); ok && e.Name == "networkIdle2" {
+				cancel()
+				close(ch)
 			}
 		})
 
@@ -490,13 +479,12 @@ func waitForEventNetworkAlmostIdle(ctx context.Context, logger *slog.Logger) fun
 
 // waitForEventLoadingFinished waits until the event LoadingFinished is fired
 // or the context timeout.
-func waitForEventLoadingFinished(ctx context.Context, logger *zap.Logger) func() error {
+func waitForEventLoadingFinished(ctx context.Context, logger *slog.Logger) func() error {
 	return func() error {
 		ch := make(chan struct{})
 		cctx, cancel := context.WithCancel(ctx)
 		chromedp.ListenTarget(cctx, func(ev any) {
-			switch ev.(type) {
-			case *network.EventLoadingFinished:
+			if _, ok := ev.(*network.EventLoadingFinished); ok {
 				cancel()
 				close(ch)
 			}
@@ -504,7 +492,7 @@ func waitForEventLoadingFinished(ctx context.Context, logger *zap.Logger) func()
 
 		select {
 		case <-ch:
-			logger.Debug("event LoadingFinished fired")
+			logger.DebugContext(ctx, "event LoadingFinished fired")
 			return nil
 		case <-ctx.Done():
 			return fmt.Errorf("wait for event LoadingFinished: %w", ctx.Err())

pkg/modules/chromium/mocks.go

@@ -2,38 +2,37 @@ package chromium
 
 import (
 	"context"
-
-	"go.uber.org/zap"
+	"log/slog"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
 // ApiMock is a mock for the [Api] interface.
 type ApiMock struct {
-	PdfMock        func(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error
-	ScreenshotMock func(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error
+	PdfMock        func(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error
+	ScreenshotMock func(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error
 }
 
-func (api *ApiMock) Pdf(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
+func (api *ApiMock) Pdf(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error {
 	return api.PdfMock(ctx, logger, url, outputPath, options)
 }
 
-func (api *ApiMock) Screenshot(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error {
+func (api *ApiMock) Screenshot(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error {
 	return api.ScreenshotMock(ctx, logger, url, outputPath, options)
 }
 
 // browserMock is a mock for the [browser] interface.
 type browserMock struct {
 	gotenberg.ProcessMock
-	pdfMock        func(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error
-	screenshotMock func(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error
+	pdfMock        func(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error
+	screenshotMock func(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error
 }
 
-func (b *browserMock) pdf(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
+func (b *browserMock) pdf(ctx context.Context, logger *slog.Logger, url, outputPath string, options PdfOptions) error {
 	return b.pdfMock(ctx, logger, url, outputPath, options)
 }
 
-func (b *browserMock) screenshot(ctx context.Context, logger *zap.Logger, url, outputPath string, options ScreenshotOptions) error {
+func (b *browserMock) screenshot(ctx context.Context, logger *slog.Logger, url, outputPath string, options ScreenshotOptions) error {
 	return b.screenshotMock(ctx, logger, url, outputPath, options)
 }
 

pkg/modules/chromium/routes.go

@@ -187,10 +187,8 @@ func FormDataChromiumOptions(ctx *api.Context) (*api.FormData, Options) {
 							invalidScopeToken = true
 							break
 						}
-					} else {
-						if token != "" {
-							valueTokens = append(valueTokens, token)
-						}
+					} else if token != "" {
+						valueTokens = append(valueTokens, token)
 					}
 				}
 

pkg/modules/chromium/tasks.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"time"
 
@@ -13,16 +14,15 @@ import (
 	"github.com/chromedp/cdproto/network"
 	"github.com/chromedp/cdproto/page"
 	"github.com/chromedp/chromedp"
-	"go.uber.org/zap"
 )
 
-func printToPdfActionFunc(logger *zap.Logger, outputPath string, options PdfOptions) chromedp.ActionFunc {
+func printToPdfActionFunc(logger *slog.Logger, outputPath string, options PdfOptions) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		paperHeight := options.PaperHeight
 		pageRanges := options.PageRanges
 
 		if options.SinglePage {
-			logger.Debug("single page PDF")
+			logger.DebugContext(ctx, "single page PDF")
 
 			_, _, _, _, _, cssContentSize, err := page.GetLayoutMetrics().Do(ctx)
 			if err != nil {
@@ -56,11 +56,11 @@ func printToPdfActionFunc(logger *zap.Logger, outputPath string, options PdfOpti
 			options.FooterTemplate != DefaultPdfOptions().FooterTemplate
 
 		if !hasCustomHeaderFooter {
-			logger.Debug("no custom header nor footer")
+			logger.DebugContext(ctx, "no custom header nor footer")
 
 			printToPdf = printToPdf.WithDisplayHeaderFooter(false)
 		} else {
-			logger.Debug("with custom header and/or footer")
+			logger.DebugContext(ctx, "with custom header and/or footer")
 
 			printToPdf = printToPdf.
 				WithDisplayHeaderFooter(true).
@@ -68,7 +68,7 @@ func printToPdfActionFunc(logger *zap.Logger, outputPath string, options PdfOpti
 				WithFooterTemplate(options.FooterTemplate)
 		}
 
-		logger.Debug(fmt.Sprintf("print to PDF with: %+v", printToPdf))
+		logger.DebugContext(ctx, fmt.Sprintf("print to PDF with: %+v", printToPdf))
 
 		_, stream, err := printToPdf.Do(ctx)
 		if err != nil {
@@ -86,7 +86,7 @@ func printToPdfActionFunc(logger *zap.Logger, outputPath string, options PdfOpti
 		defer func() {
 			err = reader.Close()
 			if err != nil {
-				logger.Error(fmt.Sprintf("close reader: %s", err))
+				logger.ErrorContext(ctx, fmt.Sprintf("close reader: %s", err))
 			}
 		}()
 
@@ -98,7 +98,7 @@ func printToPdfActionFunc(logger *zap.Logger, outputPath string, options PdfOpti
 		defer func() {
 			err = file.Close()
 			if err != nil {
-				logger.Error(fmt.Sprintf("close output path: %s", err))
+				logger.ErrorContext(ctx, fmt.Sprintf("close output path: %s", err))
 			}
 		}()
 
@@ -113,7 +113,7 @@ func printToPdfActionFunc(logger *zap.Logger, outputPath string, options PdfOpti
 	}
 }
 
-func captureScreenshotActionFunc(logger *zap.Logger, outputPath string, options ScreenshotOptions) chromedp.ActionFunc {
+func captureScreenshotActionFunc(logger *slog.Logger, outputPath string, options ScreenshotOptions) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		captureScreenshot := page.CaptureScreenshot().
 			WithCaptureBeyondViewport(true).
@@ -134,7 +134,7 @@ func captureScreenshotActionFunc(logger *zap.Logger, outputPath string, options
 				WithQuality(int64(options.Quality))
 		}
 
-		logger.Debug(fmt.Sprintf("capture screenshot with: %+v", captureScreenshot))
+		logger.DebugContext(ctx, fmt.Sprintf("capture screenshot with: %+v", captureScreenshot))
 
 		buffer, err := captureScreenshot.Do(ctx)
 		if err != nil {
@@ -149,7 +149,7 @@ func captureScreenshotActionFunc(logger *zap.Logger, outputPath string, options
 		defer func() {
 			err = file.Close()
 			if err != nil {
-				logger.Error(fmt.Sprintf("close output path: %s", err))
+				logger.ErrorContext(ctx, fmt.Sprintf("close output path: %s", err))
 			}
 		}()
 
@@ -162,9 +162,9 @@ func captureScreenshotActionFunc(logger *zap.Logger, outputPath string, options
 	}
 }
 
-func setDeviceMetricsOverride(logger *zap.Logger, width, height int) chromedp.ActionFunc {
+func setDeviceMetricsOverride(logger *slog.Logger, width, height int) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
-		logger.Debug("set device metrics override")
+		logger.DebugContext(ctx, "set device metrics override")
 
 		err := emulation.SetDeviceMetricsOverride(int64(width), int64(height), 1.0, false).Do(ctx)
 		if err == nil {
@@ -175,15 +175,15 @@ func setDeviceMetricsOverride(logger *zap.Logger, width, height int) chromedp.Ac
 	}
 }
 
-func clearCacheActionFunc(logger *zap.Logger, clear bool) chromedp.ActionFunc {
+func clearCacheActionFunc(logger *slog.Logger, clear bool) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		// See https://github.com/gotenberg/gotenberg/issues/753.
 		if !clear {
-			logger.Debug("cache not cleared")
+			logger.DebugContext(ctx, "cache not cleared")
 			return nil
 		}
 
-		logger.Debug("clear cache")
+		logger.DebugContext(ctx, "clear cache")
 
 		err := network.ClearBrowserCache().Do(ctx)
 		if err == nil {
@@ -194,15 +194,15 @@ func clearCacheActionFunc(logger *zap.Logger, clear bool) chromedp.ActionFunc {
 	}
 }
 
-func clearCookiesActionFunc(logger *zap.Logger, clear bool) chromedp.ActionFunc {
+func clearCookiesActionFunc(logger *slog.Logger, clear bool) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		// See https://github.com/gotenberg/gotenberg/issues/753.
 		if !clear {
-			logger.Debug("cookies not cleared")
+			logger.DebugContext(ctx, "cookies not cleared")
 			return nil
 		}
 
-		logger.Debug("clear cookies")
+		logger.DebugContext(ctx, "clear cookies")
 
 		err := network.ClearBrowserCookies().Do(ctx)
 		if err == nil {
@@ -213,15 +213,15 @@ func clearCookiesActionFunc(logger *zap.Logger, clear bool) chromedp.ActionFunc
 	}
 }
 
-func disableJavaScriptActionFunc(logger *zap.Logger, disable bool) chromedp.ActionFunc {
+func disableJavaScriptActionFunc(logger *slog.Logger, disable bool) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		// See https://github.com/gotenberg/gotenberg/issues/175.
 		if !disable {
-			logger.Debug("JavaScript not disabled")
+			logger.DebugContext(ctx, "JavaScript not disabled")
 			return nil
 		}
 
-		logger.Debug("disable JavaScript")
+		logger.DebugContext(ctx, "disable JavaScript")
 
 		err := emulation.SetScriptExecutionDisabled(true).Do(ctx)
 		if err == nil {
@@ -232,10 +232,10 @@ func disableJavaScriptActionFunc(logger *zap.Logger, disable bool) chromedp.Acti
 	}
 }
 
-func setCookiesActionFunc(logger *zap.Logger, cookies []Cookie) chromedp.ActionFunc {
+func setCookiesActionFunc(logger *slog.Logger, cookies []Cookie) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		if len(cookies) == 0 {
-			logger.Debug("no cookies to set")
+			logger.DebugContext(ctx, "no cookies to set")
 			return nil
 		}
 
@@ -274,21 +274,21 @@ func setCookiesActionFunc(logger *zap.Logger, cookies []Cookie) chromedp.ActionF
 				return fmt.Errorf("set cookie %s: %w", cookiePretty(cookieParams), err)
 			}
 
-			logger.Debug(fmt.Sprintf("set cookie %s", cookiePretty(cookieParams)))
+			logger.DebugContext(ctx, fmt.Sprintf("set cookie %s", cookiePretty(cookieParams)))
 		}
 
 		return nil
 	}
 }
 
-func userAgentOverride(logger *zap.Logger, userAgent string) chromedp.ActionFunc {
+func userAgentOverride(logger *slog.Logger, userAgent string) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		if len(userAgent) == 0 {
-			logger.Debug("no user agent override")
+			logger.DebugContext(ctx, "no user agent override")
 			return nil
 		}
 
-		logger.Debug(fmt.Sprintf("user agent override: %s", userAgent))
+		logger.DebugContext(ctx, fmt.Sprintf("user agent override: %s", userAgent))
 		err := emulation.SetUserAgentOverride(userAgent).Do(ctx)
 		if err == nil {
 			return nil
@@ -303,32 +303,32 @@ func userAgentOverride(logger *zap.Logger, userAgent string) chromedp.ActionFunc
 // network.SetExtraHTTPHeaders set the headers for ALL requests from the page.
 // See https://github.com/gotenberg/gotenberg/issues/1011.
 //
-//func extraHttpHeadersActionFunc(logger *zap.Logger, extraHttpHeaders map[string]string) chromedp.ActionFunc {
-//	return func(ctx context.Context) error {
-//		if len(extraHttpHeaders) == 0 {
-//			logger.Debug("no extra HTTP headers")
-//			return nil
-//		}
+//  func extraHttpHeadersActionFunc(logger *slog.Logger, extraHttpHeaders map[string]string) chromedp.ActionFunc {
+// 	return func(ctx context.Context) error {
+// 		if len(extraHttpHeaders) == 0 {
+// 			logger.DebugContext(ctx,"no extra HTTP headers")
+// 			return nil
+// 		}
 //
-//		logger.Debug(fmt.Sprintf("extra HTTP headers: %+v", extraHttpHeaders))
+// 		logger.DebugContext(ctx,fmt.Sprintf("extra HTTP headers: %+v", extraHttpHeaders))
 //
-//		headers := make(network.Headers, len(extraHttpHeaders))
-//		for key, value := range extraHttpHeaders {
-//			headers[key] = value
-//		}
+// 		headers := make(network.Headers, len(extraHttpHeaders))
+// 		for key, value := range extraHttpHeaders {
+// 			headers[key] = value
+// 		}
 //
-//		err := network.SetExtraHTTPHeaders(headers).Do(ctx)
-//		if err == nil {
-//			return nil
-//		}
+// 		err := network.SetExtraHTTPHeaders(headers).Do(ctx)
+// 		if err == nil {
+// 			return nil
+// 		}
 //
-//		return fmt.Errorf("set extra HTTP headers: %w", err)
-//	}
-//}
+// 		return fmt.Errorf("set extra HTTP headers: %w", err)
+// 	}
+// }
 
-func navigateActionFunc(logger *zap.Logger, url string, skipNetworkIdleEvent, skipNetworkAlmostIdleEvent bool) chromedp.ActionFunc {
+func navigateActionFunc(logger *slog.Logger, url string, skipNetworkIdleEvent, skipNetworkAlmostIdleEvent bool) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
-		logger.Debug(fmt.Sprintf("navigate to '%s'", url))
+		logger.DebugContext(ctx, fmt.Sprintf("navigate to '%s'", url))
 
 		_, _, _, _, err := page.Navigate(url).Do(ctx)
 		if err != nil {
@@ -344,13 +344,13 @@ func navigateActionFunc(logger *zap.Logger, url string, skipNetworkIdleEvent, sk
 		if !skipNetworkIdleEvent {
 			waitFunc = append(waitFunc, waitForEventNetworkIdle(ctx, logger))
 		} else {
-			logger.Debug("skipping network idle event")
+			logger.DebugContext(ctx, "skipping network idle event")
 		}
 
 		if !skipNetworkAlmostIdleEvent {
 			waitFunc = append(waitFunc, waitForEventNetworkAlmostIdle(ctx, logger))
 		} else {
-			logger.Debug("skipping network almost idle event")
+			logger.DebugContext(ctx, "skipping network almost idle event")
 		}
 
 		err = runBatch(
@@ -366,11 +366,11 @@ func navigateActionFunc(logger *zap.Logger, url string, skipNetworkIdleEvent, sk
 	}
 }
 
-func hideDefaultWhiteBackgroundActionFunc(logger *zap.Logger, omitBackground, printBackground bool) chromedp.ActionFunc {
+func hideDefaultWhiteBackgroundActionFunc(logger *slog.Logger, omitBackground, printBackground bool) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		// See https://github.com/gotenberg/gotenberg/issues/226.
 		if !omitBackground {
-			logger.Debug("default white background not hidden")
+			logger.DebugContext(ctx, "default white background not hidden")
 			return nil
 		}
 
@@ -379,7 +379,7 @@ func hideDefaultWhiteBackgroundActionFunc(logger *zap.Logger, omitBackground, pr
 			return fmt.Errorf("validate omit background: %w", ErrOmitBackgroundWithoutPrintBackground)
 		}
 
-		logger.Debug("hide default white background")
+		logger.DebugContext(ctx, "hide default white background")
 
 		err := emulation.SetDefaultBackgroundColorOverride().WithColor(
 			&cdp.RGBA{
@@ -397,7 +397,7 @@ func hideDefaultWhiteBackgroundActionFunc(logger *zap.Logger, omitBackground, pr
 	}
 }
 
-func forceExactColorsActionFunc(logger *zap.Logger, printBackground bool) chromedp.ActionFunc {
+func forceExactColorsActionFunc(logger *slog.Logger, printBackground bool) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		css := "html { -webkit-print-color-adjust: exact !important; }"
 		if !printBackground {
@@ -405,7 +405,7 @@ func forceExactColorsActionFunc(logger *zap.Logger, printBackground bool) chrome
 			// print of the background, whatever the printToPDF args.
 			// See https://github.com/gotenberg/gotenberg/issues/1154.
 			additionalCss := "html, body { background: none !important; }"
-			logger.Debug(fmt.Sprintf("inject %s as printBackground is %t", additionalCss, printBackground))
+			logger.DebugContext(ctx, fmt.Sprintf("inject %s as printBackground is %t", additionalCss, printBackground))
 			css += additionalCss
 		}
 
@@ -429,10 +429,10 @@ func forceExactColorsActionFunc(logger *zap.Logger, printBackground bool) chrome
 	}
 }
 
-func emulateMediaTypeActionFunc(logger *zap.Logger, mediaType string, mediaFeatures []EmulatedMediaFeature) chromedp.ActionFunc {
+func emulateMediaTypeActionFunc(logger *slog.Logger, mediaType string, mediaFeatures []EmulatedMediaFeature) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		if mediaType == "" && len(mediaFeatures) == 0 {
-			logger.Debug("no emulated media type or features")
+			logger.DebugContext(ctx, "no emulated media type or features")
 			return nil
 		}
 
@@ -443,12 +443,12 @@ func emulateMediaTypeActionFunc(logger *zap.Logger, mediaType string, mediaFeatu
 		emulatedMedia := emulation.SetEmulatedMedia()
 
 		if mediaType != "" {
-			logger.Debug(fmt.Sprintf("emulate media type '%s'", mediaType))
+			logger.DebugContext(ctx, fmt.Sprintf("emulate media type '%s'", mediaType))
 			emulatedMedia = emulatedMedia.WithMedia(mediaType)
 		}
 
 		if len(mediaFeatures) > 0 {
-			logger.Debug(fmt.Sprintf("emulate media features %+v", mediaFeatures))
+			logger.DebugContext(ctx, fmt.Sprintf("emulate media features %+v", mediaFeatures))
 
 			features := make([]*emulation.MediaFeature, len(mediaFeatures))
 			for i, f := range mediaFeatures {
@@ -470,21 +470,21 @@ func emulateMediaTypeActionFunc(logger *zap.Logger, mediaType string, mediaFeatu
 	}
 }
 
-func waitDelayBeforePrintActionFunc(logger *zap.Logger, disableJavaScript bool, delay time.Duration) chromedp.ActionFunc {
+func waitDelayBeforePrintActionFunc(logger *slog.Logger, disableJavaScript bool, delay time.Duration) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		if disableJavaScript {
-			logger.Debug("JavaScript disabled, skipping wait delay")
+			logger.DebugContext(ctx, "JavaScript disabled, skipping wait delay")
 			return nil
 		}
 
 		if delay <= 0 {
-			logger.Debug("no wait delay")
+			logger.DebugContext(ctx, "no wait delay")
 			return nil
 		}
 
 		// We wait for a given amount of time so that JavaScript
 		// scripts have a chance to finish before printing the page.
-		logger.Debug(fmt.Sprintf("wait '%s' before print", delay))
+		logger.DebugContext(ctx, fmt.Sprintf("wait '%s' before print", delay))
 
 		select {
 		case <-ctx.Done():
@@ -495,21 +495,21 @@ func waitDelayBeforePrintActionFunc(logger *zap.Logger, disableJavaScript bool,
 	}
 }
 
-func waitForExpressionBeforePrintActionFunc(logger *zap.Logger, disableJavaScript bool, expression string) chromedp.ActionFunc {
+func waitForExpressionBeforePrintActionFunc(logger *slog.Logger, disableJavaScript bool, expression string) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		if disableJavaScript {
-			logger.Debug("JavaScript disabled, skipping wait expression")
+			logger.DebugContext(ctx, "JavaScript disabled, skipping wait expression")
 			return nil
 		}
 
 		if expression == "" {
-			logger.Debug("no wait expression")
+			logger.DebugContext(ctx, "no wait expression")
 			return nil
 		}
 
 		// We wait until the evaluation of the expression is true or
 		// until the context is done.
-		logger.Debug(fmt.Sprintf("wait until '%s' is true before print", expression))
+		logger.DebugContext(ctx, fmt.Sprintf("wait until '%s' is true before print", expression))
 		ticker := time.NewTicker(time.Duration(100) * time.Millisecond)
 
 		for {
@@ -537,14 +537,14 @@ func waitForExpressionBeforePrintActionFunc(logger *zap.Logger, disableJavaScrip
 	}
 }
 
-func waitForSelectorVisibleBeforePrintActionFunc(logger *zap.Logger, selector string) chromedp.ActionFunc {
+func waitForSelectorVisibleBeforePrintActionFunc(logger *slog.Logger, selector string) chromedp.ActionFunc {
 	return func(ctx context.Context) error {
 		if selector == "" {
-			logger.Debug("no wait selector")
+			logger.DebugContext(ctx, "no wait selector")
 			return nil
 		}
 
-		logger.Debug(fmt.Sprintf("wait until '%s' is visible before print", selector))
+		logger.DebugContext(ctx, fmt.Sprintf("wait until '%s' is visible before print", selector))
 		err := chromedp.WaitVisible(selector, chromedp.ByQuery, chromedp.RetryInterval(time.Duration(100)*time.Millisecond)).Do(ctx)
 		if err != nil {
 			return fmt.Errorf("wait visible: %v: %w", err, ErrInvalidSelectorQuery)

pkg/modules/exiftool/exiftool.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/exec"
 	"reflect"
@@ -11,7 +12,6 @@ import (
 	"syscall"
 
 	"github.com/barasher/go-exiftool"
-	"go.uber.org/zap"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
@@ -74,27 +74,27 @@ func (engine *ExifTool) Debug() map[string]any {
 }
 
 // Merge is not available in this implementation.
-func (engine *ExifTool) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+func (engine *ExifTool) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
 	return fmt.Errorf("merge PDFs with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Split is not available in this implementation.
-func (engine *ExifTool) Split(ctx context.Context, logger *zap.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
+func (engine *ExifTool) Split(ctx context.Context, logger *slog.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
 	return nil, fmt.Errorf("split PDF with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Flatten is not available in this implementation.
-func (engine *ExifTool) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
+func (engine *ExifTool) Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error {
 	return fmt.Errorf("flatten PDF with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Convert is not available in this implementation.
-func (engine *ExifTool) Convert(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+func (engine *ExifTool) Convert(ctx context.Context, logger *slog.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
 	return fmt.Errorf("convert PDF to '%+v' with ExifTool: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadMetadata extracts the metadata of a given PDF file.
-func (engine *ExifTool) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error) {
+func (engine *ExifTool) ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error) {
 	exifTool, err := exiftool.NewExiftool(exiftool.SetExiftoolBinaryPath(engine.binPath))
 	if err != nil {
 		return nil, fmt.Errorf("new ExifTool: %w", err)
@@ -103,7 +103,7 @@ func (engine *ExifTool) ReadMetadata(ctx context.Context, logger *zap.Logger, in
 	defer func(exifTool *exiftool.Exiftool) {
 		err := exifTool.Close()
 		if err != nil {
-			logger.Error(fmt.Sprintf("close ExifTool: %v", err))
+			logger.ErrorContext(ctx, fmt.Sprintf("close ExifTool: %v", err))
 		}
 	}(exifTool)
 
@@ -116,7 +116,7 @@ func (engine *ExifTool) ReadMetadata(ctx context.Context, logger *zap.Logger, in
 }
 
 // WriteMetadata writes the metadata into a given PDF file.
-func (engine *ExifTool) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error {
+func (engine *ExifTool) WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error {
 	exifTool, err := exiftool.NewExiftool(exiftool.SetExiftoolBinaryPath(engine.binPath))
 	if err != nil {
 		return fmt.Errorf("new ExifTool: %w", err)
@@ -125,7 +125,7 @@ func (engine *ExifTool) WriteMetadata(ctx context.Context, logger *zap.Logger, m
 	defer func(exifTool *exiftool.Exiftool) {
 		err := exifTool.Close()
 		if err != nil {
-			logger.Error(fmt.Sprintf("close ExifTool: %v", err))
+			logger.ErrorContext(ctx, fmt.Sprintf("close ExifTool: %v", err))
 		}
 	}(exifTool)
 
@@ -204,7 +204,7 @@ func (engine *ExifTool) WriteMetadata(ctx context.Context, logger *zap.Logger, m
 }
 
 // PageCount returns the number of pages in a PDF file using ExifTool.
-func (engine *ExifTool) PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error) {
+func (engine *ExifTool) PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error) {
 	metadata, err := engine.ReadMetadata(ctx, logger, inputPath)
 	if err != nil {
 		return 0, fmt.Errorf("read metadata with ExifTool: %w", err)
@@ -235,37 +235,37 @@ func (engine *ExifTool) PageCount(ctx context.Context, logger *zap.Logger, input
 }
 
 // WriteBookmarks is not available in this implementation.
-func (engine *ExifTool) WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
+func (engine *ExifTool) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
 	return fmt.Errorf("write PDF bookmarks with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadBookmarks is not available in this implementation.
-func (engine *ExifTool) ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
+func (engine *ExifTool) ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
 	return nil, fmt.Errorf("read PDF bookmarks with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Encrypt is not available in this implementation.
-func (engine *ExifTool) Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error {
+func (engine *ExifTool) Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error {
 	return fmt.Errorf("encrypt PDF using ExifTool: %w", gotenberg.ErrPdfEncryptionNotSupported)
 }
 
 // EmbedFiles is not available in this implementation.
-func (engine *ExifTool) EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error {
+func (engine *ExifTool) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {
 	return fmt.Errorf("embed files with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Watermark is not available in this implementation.
-func (engine *ExifTool) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *ExifTool) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return fmt.Errorf("watermark PDF with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Stamp is not available in this implementation.
-func (engine *ExifTool) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *ExifTool) Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return fmt.Errorf("stamp PDF with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Rotate is not available in this implementation.
-func (engine *ExifTool) Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error {
+func (engine *ExifTool) Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error {
 	return fmt.Errorf("rotate PDF with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 

pkg/modules/libreoffice/api/api.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/exec"
 	"strings"
@@ -12,8 +13,9 @@ import (
 
 	"github.com/alexliesenfeld/health"
 	flag "github.com/spf13/pflag"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
 	"go.uber.org/multierr"
-	"go.uber.org/zap"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 	"github.com/gotenberg/gotenberg/v8/pkg/modules/api"
@@ -45,9 +47,15 @@ type Api struct {
 	autoStart bool
 	args      libreOfficeArguments
 
-	logger      *zap.Logger
+	logger      *slog.Logger
 	libreOffice libreOffice
 	supervisor  gotenberg.ProcessSupervisor
+
+	reqsCounter               metric.Int64Counter
+	errsCounter               metric.Int64Counter
+	conversionDurationCounter metric.Float64Histogram
+	queueWaitDurationCounter  metric.Float64Histogram
+	pdfOutputSizeCounter      metric.Int64Histogram
 }
 
 // Options gathers available options when converting a document to PDF.
@@ -216,7 +224,7 @@ func DefaultOptions() Options {
 
 // Uno is an abstraction on top of the Universal Network Objects API.
 type Uno interface {
-	Pdf(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error
+	Pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error
 	Extensions() []string
 }
 
@@ -270,20 +278,108 @@ func (a *Api) Provision(ctx *gotenberg.Context) error {
 	}
 
 	// Logger.
-	loggerProvider, err := ctx.Module(new(gotenberg.LoggerProvider))
-	if err != nil {
-		return fmt.Errorf("get logger provider: %w", err)
-	}
-	logger, err := loggerProvider.(gotenberg.LoggerProvider).Logger(a)
-	if err != nil {
-		return fmt.Errorf("get logger: %w", err)
-	}
-	a.logger = logger.Named("libreoffice")
+	a.logger = gotenberg.Logger(a).With(slog.String("logger", "libreoffice"))
 
 	// Process.
 	a.libreOffice = newLibreOfficeProcess(a.args)
 	a.supervisor = gotenberg.NewProcessSupervisor(a.logger, a.libreOffice, flags.MustInt64("libreoffice-restart-after"), flags.MustInt64("libreoffice-max-queue-size"), 1)
 
+	// Metrics.
+	meter := gotenberg.Meter()
+
+	// Observable gauges.
+	var err error
+
+	_, err = meter.Int64ObservableGauge(
+		"libreoffice.requests.active",
+		metric.WithDescription("Current number of active LibreOffice requests"),
+		metric.WithUnit("{request}"),
+		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
+			o.Observe(a.supervisor.ActiveTasksCount())
+			return nil
+		}),
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.requests.active gauge: %w", err)
+	}
+
+	_, err = meter.Int64ObservableGauge(
+		"libreoffice.requests.queue_size",
+		metric.WithDescription("Current number of LibreOffice conversion requests waiting to be treated"),
+		metric.WithUnit("{request}"),
+		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
+			o.Observe(a.supervisor.ReqQueueSize())
+			return nil
+		}),
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.requests.queue_size gauge: %w", err)
+	}
+
+	_, err = meter.Int64ObservableCounter(
+		"libreoffice.process.restarts.total",
+		metric.WithDescription("Current number of LibreOffice restarts"),
+		metric.WithUnit("{restart}"),
+		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
+			o.Observe(a.supervisor.RestartsCount())
+			return nil
+		}),
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.process.restarts.total counter: %w", err)
+	}
+
+	// Counters.
+	a.reqsCounter, err = meter.Int64Counter(
+		"libreoffice.requests.total",
+		metric.WithDescription("Total number of LibreOffice conversion requests"),
+		metric.WithUnit("{request}"),
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.requests.total counter: %w", err)
+	}
+
+	a.errsCounter, err = meter.Int64Counter(
+		"libreoffice.errors.total",
+		metric.WithDescription("Total number of LibreOffice conversion errors"),
+		metric.WithUnit("{error}"),
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.errors.total counter: %w", err)
+	}
+
+	// Histograms.
+	durationBuckets := metric.WithExplicitBucketBoundaries(0.5, 1, 2, 5, 10, 30, 60)
+
+	a.conversionDurationCounter, err = meter.Float64Histogram(
+		"libreoffice.conversion.duration",
+		metric.WithDescription("Duration of LibreOffice conversions"),
+		metric.WithUnit("s"),
+		durationBuckets,
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.conversion.duration histogram: %w", err)
+	}
+
+	a.queueWaitDurationCounter, err = meter.Float64Histogram(
+		"libreoffice.queue.wait.duration",
+		metric.WithDescription("Duration of waiting in queue for LibreOffice conversions"),
+		metric.WithUnit("s"),
+		durationBuckets,
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.queue.wait.duration histogram: %w", err)
+	}
+
+	a.pdfOutputSizeCounter, err = meter.Int64Histogram(
+		"libreoffice.pdf.output.size",
+		metric.WithDescription("Size of PDF output from LibreOffice conversions"),
+		metric.WithUnit("By"),
+	)
+	if err != nil {
+		return fmt.Errorf("create libreoffice.pdf.output.size histogram: %w", err)
+	}
+
 	return nil
 }
 
@@ -332,7 +428,7 @@ func (a *Api) StartupMessage() string {
 func (a *Api) Stop(ctx context.Context) error {
 	// Block until the context is done so that another module may gracefully
 	// stop before we do a shutdown.
-	a.logger.Debug("wait for the end of grace duration")
+	a.logger.DebugContext(ctx, "wait for the end of grace duration")
 
 	<-ctx.Done()
 
@@ -431,18 +527,64 @@ func (a *Api) LibreOffice() (Uno, error) {
 }
 
 // Pdf converts a document to PDF.
-func (a *Api) Pdf(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error {
+func (a *Api) Pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error {
+	start := time.Now()
+	var conversionStart time.Time
+
 	err := a.supervisor.Run(ctx, logger, func() error {
+		conversionStart = time.Now()
 		return a.libreOffice.pdf(ctx, logger, inputPath, outputPath, options)
 	})
 
+	// Determine status and error reason.
+	status := "success"
+	reason := ""
+
+	if err != nil {
+		switch {
+		case errors.Is(err, context.DeadlineExceeded):
+			status = "timeout"
+			reason = "timeout"
+		case errors.Is(err, context.Canceled):
+			status = "error"
+			reason = "context_cancelled"
+		case errors.Is(err, gotenberg.ErrMaximumQueueSizeExceeded) || errors.Is(err, gotenberg.ErrProcessAlreadyRestarting):
+			status = "error"
+			reason = "libreoffice_unavailable"
+		default:
+			status = "error"
+			reason = "unknown"
+		}
+	}
+
+	// Record metrics.
+	attrs := metric.WithAttributes(attribute.String("status", status))
+	a.reqsCounter.Add(ctx, 1, attrs)
+
+	if reason != "" {
+		a.errsCounter.Add(ctx, 1, metric.WithAttributes(attribute.String("reason", reason)))
+	}
+
+	if !conversionStart.IsZero() {
+		queueWait := conversionStart.Sub(start).Seconds()
+		a.queueWaitDurationCounter.Record(ctx, queueWait, attrs)
+
+		conversionDuration := time.Since(conversionStart).Seconds()
+		a.conversionDurationCounter.Record(ctx, conversionDuration, attrs)
+	}
+
 	if err == nil {
+		stat, statErr := os.Stat(outputPath)
+		if statErr == nil {
+			a.pdfOutputSizeCounter.Record(ctx, stat.Size(), attrs)
+		}
+
 		return nil
 	}
 
 	// See https://github.com/gotenberg/gotenberg/issues/639.
 	if errors.Is(err, ErrCoreDumped) {
-		logger.Debug(fmt.Sprintf("got a '%s' error, retry conversion", err))
+		logger.DebugContext(ctx, fmt.Sprintf("got a '%s' error, retry conversion", err))
 		return a.Pdf(ctx, logger, inputPath, outputPath, options)
 	}
 

pkg/modules/libreoffice/api/freeport.go

@@ -1,14 +1,14 @@
 package api
 
 import (
+	"context"
 	"fmt"
+	"log/slog"
 	"net"
 	"strconv"
-
-	"go.uber.org/zap"
 )
 
-func freePort(logger *zap.Logger) (int, error) {
+func freePort(logger *slog.Logger) (int, error) {
 	netListener, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		return 0, fmt.Errorf("listen on the local network address: %w", err)
@@ -16,7 +16,7 @@ func freePort(logger *zap.Logger) (int, error) {
 	defer func() {
 		err := netListener.Close()
 		if err != nil {
-			logger.Error(fmt.Sprintf("close network listener: %s", err.Error()))
+			logger.ErrorContext(context.Background(), fmt.Sprintf("close network listener: %s", err.Error()))
 		}
 	}()
 

pkg/modules/libreoffice/api/libreoffice.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"net"
 	"os"
 	"strings"
@@ -11,14 +12,12 @@ import (
 	"sync/atomic"
 	"time"
 
-	"go.uber.org/zap"
-
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
 type libreOffice interface {
 	gotenberg.Process
-	pdf(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error
+	pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error
 }
 
 type libreOfficeArguments struct {
@@ -48,7 +47,7 @@ func newLibreOfficeProcess(arguments libreOfficeArguments) libreOffice {
 	return p
 }
 
-func (p *libreOfficeProcess) Start(logger *zap.Logger) error {
+func (p *libreOfficeProcess) Start(logger *slog.Logger) error {
 	if p.isStarted.Load() {
 		return errors.New("LibreOffice is already started")
 	}
@@ -86,7 +85,7 @@ func (p *libreOfficeProcess) Start(logger *zap.Logger) error {
 		return fmt.Errorf("execute LibreOffice: %w", err)
 	}
 
-	logger.Debug("got exit code 81, e.g., LibreOffice first start")
+	logger.DebugContext(context.Background(), "got exit code 81, e.g., LibreOffice first start")
 
 	// Second start (daemon).
 	cmd = gotenberg.Command(logger, p.arguments.binPath, args...)
@@ -123,7 +122,7 @@ func (p *libreOfficeProcess) Start(logger *zap.Logger) error {
 			connChan <- nil
 			err = conn.Close()
 			if err != nil {
-				logger.Debug(fmt.Sprintf("close connection after health checking the LibreOffice: %v", err))
+				logger.DebugContext(context.Background(), fmt.Sprintf("close connection after health checking the LibreOffice: %v", err))
 			}
 
 			break
@@ -148,19 +147,19 @@ func (p *libreOfficeProcess) Start(logger *zap.Logger) error {
 		// Let's make sure the process is killed.
 		err = cmd.Kill()
 		if err != nil {
-			logger.Debug(fmt.Sprintf("kill LibreOffice process: %v", err))
+			logger.DebugContext(context.Background(), fmt.Sprintf("kill LibreOffice process: %v", err))
 		}
 
 		// And the user profile directory is deleted.
 		err = os.RemoveAll(userProfileDirPath)
 		if err != nil {
-			logger.Error(fmt.Sprintf("remove LibreOffice's user profile directory: %v", err))
+			logger.ErrorContext(context.Background(), fmt.Sprintf("remove LibreOffice's user profile directory: %v", err))
 		}
 
-		logger.Debug(fmt.Sprintf("'%s' LibreOffice's user profile directory removed", userProfileDirPath))
+		logger.DebugContext(context.Background(), fmt.Sprintf("'%s' LibreOffice's user profile directory removed", userProfileDirPath))
 	}()
 
-	logger.Debug("waiting for the LibreOffice socket to be available...")
+	logger.DebugContext(context.Background(), "waiting for the LibreOffice socket to be available...")
 
 	for {
 		select {
@@ -169,7 +168,7 @@ func (p *libreOfficeProcess) Start(logger *zap.Logger) error {
 				return fmt.Errorf("LibreOffice socket not available: %w", err)
 			}
 
-			logger.Debug("LibreOffice socket available")
+			logger.DebugContext(context.Background(), "LibreOffice socket available")
 			success = true
 
 			return nil
@@ -179,7 +178,7 @@ func (p *libreOfficeProcess) Start(logger *zap.Logger) error {
 	}
 }
 
-func (p *libreOfficeProcess) Stop(logger *zap.Logger) error {
+func (p *libreOfficeProcess) Stop(logger *slog.Logger) error {
 	if !p.isStarted.Load() {
 		// No big deal? Like calling cancel twice.
 		return nil
@@ -192,15 +191,15 @@ func (p *libreOfficeProcess) Stop(logger *zap.Logger) error {
 		go func() {
 			err := os.RemoveAll(userProfileDirPath)
 			if err != nil {
-				logger.Error(fmt.Sprintf("remove LibreOffice's user profile directory: %v", err))
+				logger.ErrorContext(context.Background(), fmt.Sprintf("remove LibreOffice's user profile directory: %v", err))
 			} else {
-				logger.Debug(fmt.Sprintf("'%s' LibreOffice's user profile directory removed", userProfileDirPath))
+				logger.DebugContext(context.Background(), fmt.Sprintf("'%s' LibreOffice's user profile directory removed", userProfileDirPath))
 			}
 
 			// Also, remove LibreOffice specific files in the temporary directory.
-			err = gotenberg.GarbageCollect(logger, os.TempDir(), []string{"OSL_PIPE", ".tmp"}, expirationTime)
+			err = gotenberg.GarbageCollect(context.Background(), logger, os.TempDir(), []string{"OSL_PIPE", ".tmp"}, expirationTime)
 			if err != nil {
-				logger.Error(err.Error())
+				logger.ErrorContext(context.Background(), err.Error())
 			}
 		}()
 	}(copyUserProfileDirPath, expirationTime)
@@ -221,7 +220,7 @@ func (p *libreOfficeProcess) Stop(logger *zap.Logger) error {
 	return nil
 }
 
-func (p *libreOfficeProcess) Healthy(logger *zap.Logger) bool {
+func (p *libreOfficeProcess) Healthy(logger *slog.Logger) bool {
 	// Good to know: the supervisor does not call this method if no first start
 	// or if the process is restarting.
 
@@ -237,7 +236,7 @@ func (p *libreOfficeProcess) Healthy(logger *zap.Logger) bool {
 	if err == nil {
 		err = conn.Close()
 		if err != nil {
-			logger.Debug(fmt.Sprintf("close connection after health checking LibreOffice: %v", err))
+			logger.DebugContext(context.Background(), fmt.Sprintf("close connection after health checking LibreOffice: %v", err))
 		}
 
 		return true
@@ -246,7 +245,7 @@ func (p *libreOfficeProcess) Healthy(logger *zap.Logger) bool {
 	return false
 }
 
-func (p *libreOfficeProcess) pdf(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error {
+func (p *libreOfficeProcess) pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error {
 	if !p.isStarted.Load() {
 		return errors.New("LibreOffice not started, cannot handle PDF conversion")
 	}
@@ -259,8 +258,7 @@ func (p *libreOfficeProcess) pdf(ctx context.Context, logger *zap.Logger, inputP
 
 	args = append(args, "--port", fmt.Sprintf("%d", p.socketPort))
 
-	checkedEntry := logger.Check(zap.DebugLevel, "check for debug level before setting high verbosity")
-	if checkedEntry != nil {
+	if logger.Enabled(ctx, slog.LevelDebug) {
 		args = append(args, "-vvv")
 	}
 
@@ -362,7 +360,7 @@ func (p *libreOfficeProcess) pdf(ctx context.Context, logger *zap.Logger, inputP
 		return fmt.Errorf("create uno command: %w", err)
 	}
 
-	logger.Debug(fmt.Sprintf("print to PDF with: %+v", options))
+	logger.DebugContext(ctx, fmt.Sprintf("print to PDF with: %+v", options))
 
 	exitCode, err := cmd.Exec()
 	if err == nil {

pkg/modules/libreoffice/api/mocks.go

@@ -3,19 +3,18 @@ package api
 import (
 	"context"
 	"errors"
-
-	"go.uber.org/zap"
+	"log/slog"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
 // ApiMock is a mock for the [Uno] interface.
 type ApiMock struct {
-	PdfMock        func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error
+	PdfMock        func(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error
 	ExtensionsMock func() []string
 }
 
-func (api *ApiMock) Pdf(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error {
+func (api *ApiMock) Pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error {
 	return api.PdfMock(ctx, logger, inputPath, outputPath, options)
 }
 
@@ -37,10 +36,10 @@ type libreOfficeMock struct {
 	errCoreDumpedCount int
 
 	gotenberg.ProcessMock
-	pdfMock func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error
+	pdfMock func(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error
 }
 
-func (b *libreOfficeMock) pdf(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options Options) error {
+func (b *libreOfficeMock) pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error {
 	err := b.pdfMock(ctx, logger, inputPath, outputPath, options)
 	if errors.Is(err, ErrCoreDumped) {
 		b.errCoreDumpedCount += 1

pkg/modules/libreoffice/pdfengine/pdfengine.go

@@ -4,8 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
-
-	"go.uber.org/zap"
+	"log/slog"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 	"github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice/api"
@@ -47,17 +46,17 @@ func (engine *LibreOfficePdfEngine) Provision(ctx *gotenberg.Context) error {
 }
 
 // Merge is not available in this implementation.
-func (engine *LibreOfficePdfEngine) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+func (engine *LibreOfficePdfEngine) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
 	return fmt.Errorf("merge PDFs with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Split is not available in this implementation.
-func (engine *LibreOfficePdfEngine) Split(ctx context.Context, logger *zap.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
+func (engine *LibreOfficePdfEngine) Split(ctx context.Context, logger *slog.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
 	return nil, fmt.Errorf("split PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Flatten is not available in this implementation.
-func (engine *LibreOfficePdfEngine) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
+func (engine *LibreOfficePdfEngine) Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error {
 	return fmt.Errorf("flatten PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
@@ -65,7 +64,7 @@ func (engine *LibreOfficePdfEngine) Flatten(ctx context.Context, logger *zap.Log
 // PDF/A-1b, PDF/A-2b, PDF/A-3b and PDF/UA formats are available. If another
 // PDF format is requested, it returns a [gotenberg.ErrPdfFormatNotSupported]
 // error.
-func (engine *LibreOfficePdfEngine) Convert(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+func (engine *LibreOfficePdfEngine) Convert(ctx context.Context, logger *slog.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
 	opts := api.DefaultOptions()
 	opts.PdfFormats = formats
 	err := engine.unoApi.Pdf(ctx, logger, inputPath, outputPath, opts)
@@ -82,52 +81,52 @@ func (engine *LibreOfficePdfEngine) Convert(ctx context.Context, logger *zap.Log
 }
 
 // ReadMetadata is not available in this implementation.
-func (engine *LibreOfficePdfEngine) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error) {
+func (engine *LibreOfficePdfEngine) ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error) {
 	return nil, fmt.Errorf("read PDF metadata with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // WriteMetadata is not available in this implementation.
-func (engine *LibreOfficePdfEngine) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error {
+func (engine *LibreOfficePdfEngine) WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error {
 	return fmt.Errorf("write PDF metadata with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // PageCount is not available in this implementation.
-func (engine *LibreOfficePdfEngine) PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error) {
+func (engine *LibreOfficePdfEngine) PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error) {
 	return 0, fmt.Errorf("page count with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // WriteBookmarks is not available in this implementation.
-func (engine *LibreOfficePdfEngine) WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
+func (engine *LibreOfficePdfEngine) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
 	return fmt.Errorf("write PDF bookmarks with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadBookmarks is not available in this implementation.
-func (engine *LibreOfficePdfEngine) ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
+func (engine *LibreOfficePdfEngine) ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
 	return nil, fmt.Errorf("read PDF bookmarks with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Encrypt is not available in this implementation.
-func (engine *LibreOfficePdfEngine) Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error {
+func (engine *LibreOfficePdfEngine) Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error {
 	return fmt.Errorf("encrypt PDF using LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // EmbedFiles is not available in this implementation.
-func (engine *LibreOfficePdfEngine) EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error {
+func (engine *LibreOfficePdfEngine) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {
 	return fmt.Errorf("embed files with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Watermark is not available in this implementation.
-func (engine *LibreOfficePdfEngine) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *LibreOfficePdfEngine) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return fmt.Errorf("watermark PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Stamp is not available in this implementation.
-func (engine *LibreOfficePdfEngine) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *LibreOfficePdfEngine) Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return fmt.Errorf("stamp PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Rotate is not available in this implementation.
-func (engine *LibreOfficePdfEngine) Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error {
+func (engine *LibreOfficePdfEngine) Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error {
 	return fmt.Errorf("rotate PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 

pkg/modules/logging/doc.go

@@ -1,3 +0,0 @@
-// Package logging provides a module which creates a zap.Logger instance for
-// other modules.
-package logging

pkg/modules/logging/gcp.go

@@ -1,36 +0,0 @@
-package logging
-
-import "go.uber.org/zap/zapcore"
-
-func gcpSeverity(l zapcore.Level) string {
-	switch l {
-	case zapcore.DebugLevel:
-		return "DEBUG"
-	case zapcore.InfoLevel:
-		return "INFO"
-	case zapcore.WarnLevel:
-		return "WARNING"
-	case zapcore.ErrorLevel:
-		return "ERROR"
-	case zapcore.DPanicLevel:
-		return "CRITICAL"
-	case zapcore.PanicLevel:
-		return "ALERT"
-	case zapcore.FatalLevel:
-		return "EMERGENCY"
-	case zapcore.InvalidLevel:
-		return "DEFAULT"
-	default:
-		return "DEFAULT"
-	}
-}
-
-func gcpSeverityEncoder(l zapcore.Level, enc zapcore.PrimitiveArrayEncoder) {
-	enc.AppendString(gcpSeverity(l))
-}
-
-func gcpSeverityColorEncoder(l zapcore.Level, enc zapcore.PrimitiveArrayEncoder) {
-	severity := gcpSeverity(l)
-	c := levelToColor(l)
-	enc.AppendString(c.Add(severity))
-}

pkg/modules/logging/logging.go

@@ -1,239 +0,0 @@
-package logging
-
-import (
-	"fmt"
-	"os"
-	"time"
-
-	flag "github.com/spf13/pflag"
-	"go.uber.org/multierr"
-	"go.uber.org/zap"
-	"go.uber.org/zap/zapcore"
-	"golang.org/x/term"
-
-	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
-)
-
-func init() {
-	gotenberg.MustRegisterModule(new(Logging))
-}
-
-const (
-	errorLoggingLevel = "error"
-	warnLoggingLevel  = "warn"
-	infoLoggingLevel  = "info"
-	debugLoggingLevel = "debug"
-)
-
-const (
-	autoLoggingFormat = "auto"
-	jsonLoggingFormat = "json"
-	textLoggingFormat = "text"
-)
-
-// Logging is a module that implements the [gotenberg.LoggerProvider]
-// interface.
-type Logging struct {
-	level           string
-	format          string
-	fieldsPrefix    string
-	enableGcpFields bool
-}
-
-// Descriptor returns a [Logging]'s module descriptor.
-func (log *Logging) Descriptor() gotenberg.ModuleDescriptor {
-	return gotenberg.ModuleDescriptor{
-		ID: "logging",
-		FlagSet: func() *flag.FlagSet {
-			fs := flag.NewFlagSet("logging", flag.ExitOnError)
-			fs.String("log-level", infoLoggingLevel, fmt.Sprintf("Choose the level of logging detail. Options include %s, %s, %s, or %s", errorLoggingLevel, warnLoggingLevel, infoLoggingLevel, debugLoggingLevel))
-			fs.String("log-format", autoLoggingFormat, fmt.Sprintf("Specify the format of logging. Options include %s, %s, or %s", autoLoggingFormat, jsonLoggingFormat, textLoggingFormat))
-			fs.String("log-fields-prefix", "", "Prepend a specified prefix to each field in the logs")
-			fs.Bool("log-enable-gcp-fields", false, "Enable Google Cloud Platform fields - namely: time, message, severity")
-
-			// Deprecated flags.
-			fs.Bool("log-enable-gcp-severity", false, "Enable Google Cloud Platform severity mapping")
-			err := fs.MarkDeprecated("log-enable-gcp-severity", "use log-enable-gcp-fields instead")
-			if err != nil {
-				panic(err)
-			}
-
-			return fs
-		}(),
-		New: func() gotenberg.Module { return new(Logging) },
-	}
-}
-
-// Provision sets the log level and format.
-func (log *Logging) Provision(ctx *gotenberg.Context) error {
-	flags := ctx.ParsedFlags()
-
-	log.level = flags.MustString("log-level")
-	log.format = flags.MustString("log-format")
-	log.fieldsPrefix = flags.MustString("log-fields-prefix")
-	log.enableGcpFields = flags.MustDeprecatedBool("log-enable-gcp-severity", "log-enable-gcp-fields")
-
-	return nil
-}
-
-// Validate validates the log level and format.
-func (log *Logging) Validate() error {
-	var err error
-
-	switch log.level {
-	case errorLoggingLevel, warnLoggingLevel, infoLoggingLevel, debugLoggingLevel:
-		break
-	default:
-		err = multierr.Append(
-			err,
-			fmt.Errorf("log level must be either %s, %s, %s or %s", errorLoggingLevel, warnLoggingLevel, infoLoggingLevel, debugLoggingLevel),
-		)
-	}
-
-	switch log.format {
-	case autoLoggingFormat, jsonLoggingFormat, textLoggingFormat:
-		break
-	default:
-		err = multierr.Append(
-			err,
-			fmt.Errorf("log format must be either %s, %s or %s", autoLoggingFormat, jsonLoggingFormat, textLoggingFormat),
-		)
-	}
-
-	return err
-}
-
-// Logger returns a [zap.Logger].
-func (log *Logging) Logger(mod gotenberg.Module) (*zap.Logger, error) {
-	if logger == nil {
-		lvl, err := newLogLevel(log.level)
-		if err != nil {
-			return nil, fmt.Errorf("get log level: %w", err)
-		}
-
-		encoder, err := newLogEncoder(log.format, log.enableGcpFields)
-		if err != nil {
-			return nil, fmt.Errorf("get log encoder: %w", err)
-		}
-
-		logger = zap.New(customCore{
-			Core:         zapcore.NewCore(encoder, os.Stderr, lvl),
-			fieldsPrefix: log.fieldsPrefix,
-		})
-	}
-
-	return logger.Named(mod.Descriptor().ID), nil
-}
-
-// See https://github.com/gotenberg/gotenberg/issues/659.
-type customCore struct {
-	zapcore.Core
-	fieldsPrefix string
-}
-
-func (c customCore) With(fields []zapcore.Field) zapcore.Core {
-	if c.fieldsPrefix != "" {
-		for i := range fields {
-			fields[i].Key = c.fieldsPrefix + "_" + fields[i].Key
-		}
-	}
-
-	return customCore{
-		Core:         c.Core.With(fields),
-		fieldsPrefix: c.fieldsPrefix,
-	}
-}
-
-func (c customCore) Check(ent zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.CheckedEntry {
-	// This is a copy from the zapcore.ioCore implementation. Indeed, by doing
-	// so, we are able to prefix the fields given to the logger methods like
-	// Debug, Info, Warn, Error, etc.
-	if c.Enabled(ent.Level) {
-		return ce.AddCore(ent, c)
-	}
-
-	return ce
-}
-
-func (c customCore) Write(entry zapcore.Entry, fields []zapcore.Field) error {
-	if c.fieldsPrefix != "" {
-		for i := range fields {
-			fields[i].Key = c.fieldsPrefix + "_" + fields[i].Key
-		}
-	}
-
-	return c.Core.Write(entry, fields)
-}
-
-func newLogLevel(level string) (zapcore.Level, error) {
-	lvl := zapcore.InvalidLevel
-
-	err := lvl.UnmarshalText([]byte(level))
-	if err != nil {
-		return lvl, fmt.Errorf("%q is not a recognized log level: %w", level, err)
-	}
-
-	return lvl, nil
-}
-
-func newLogEncoder(format string, gcpFields bool) (zapcore.Encoder, error) {
-	isTerminal := term.IsTerminal(int(os.Stdout.Fd())) // #nosec
-	encCfg := zap.NewProductionEncoderConfig()
-
-	// Normalize the log format based on the output device.
-	if format == autoLoggingFormat {
-		if isTerminal {
-			format = textLoggingFormat
-		} else {
-			format = jsonLoggingFormat
-		}
-	}
-
-	// Use a human-readable time format if running in a terminal.
-	if isTerminal {
-		encCfg.EncodeTime = func(ts time.Time, encoder zapcore.PrimitiveArrayEncoder) {
-			encoder.AppendString(ts.Local().Format("2006/01/02 15:04:05.000"))
-		}
-	}
-
-	// Configure level encoding based on format and GCP settings.
-	if format == textLoggingFormat && isTerminal {
-		if gcpFields {
-			encCfg.EncodeLevel = gcpSeverityColorEncoder
-		} else {
-			encCfg.EncodeLevel = zapcore.CapitalColorLevelEncoder
-		}
-	}
-
-	// For non-text (JSON) or when GCP fields are requested outside a terminal text output,
-	// adjust the configuration to use GCP-specific field names and encoders.
-	if gcpFields && format != textLoggingFormat {
-		encCfg.EncodeLevel = gcpSeverityEncoder
-		encCfg.TimeKey = "time"
-		encCfg.LevelKey = "severity"
-		encCfg.MessageKey = "message"
-		encCfg.EncodeTime = zapcore.ISO8601TimeEncoder
-		encCfg.EncodeDuration = zapcore.MillisDurationEncoder
-	}
-
-	switch format {
-	case textLoggingFormat:
-		return zapcore.NewConsoleEncoder(encCfg), nil
-	case jsonLoggingFormat:
-		return zapcore.NewJSONEncoder(encCfg), nil
-	default:
-		return nil, fmt.Errorf("%s is not a recognized log format", format)
-	}
-}
-
-// Singleton so that we instantiate our logger only once.
-var logger *zap.Logger = nil
-
-// Interface guards.
-var (
-	_ gotenberg.Module         = (*Logging)(nil)
-	_ gotenberg.Provisioner    = (*Logging)(nil)
-	_ gotenberg.Validator      = (*Logging)(nil)
-	_ gotenberg.LoggerProvider = (*Logging)(nil)
-	_ zapcore.Core             = (*customCore)(nil)
-)

pkg/modules/pdfcpu/pdfcpu.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -14,8 +15,6 @@ import (
 	"strings"
 	"syscall"
 
-	"go.uber.org/zap"
-
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
@@ -96,7 +95,7 @@ func (engine *PdfCpu) Debug() map[string]any {
 }
 
 // Merge combines multiple PDFs into a single PDF.
-func (engine *PdfCpu) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+func (engine *PdfCpu) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
 	args := make([]string, 0, 2+len(inputPaths))
 	args = append(args, "merge", outputPath)
 	args = append(args, inputPaths...)
@@ -115,7 +114,7 @@ func (engine *PdfCpu) Merge(ctx context.Context, logger *zap.Logger, inputPaths
 }
 
 // Split splits a given PDF file.
-func (engine *PdfCpu) Split(ctx context.Context, logger *zap.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
+func (engine *PdfCpu) Split(ctx context.Context, logger *slog.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
 	var args []string
 
 	switch mode.Mode {
@@ -165,32 +164,32 @@ func (engine *PdfCpu) Split(ctx context.Context, logger *zap.Logger, mode gotenb
 }
 
 // Flatten is not available in this implementation.
-func (engine *PdfCpu) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
+func (engine *PdfCpu) Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error {
 	return fmt.Errorf("flatten PDF with pdfcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Convert is not available in this implementation.
-func (engine *PdfCpu) Convert(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+func (engine *PdfCpu) Convert(ctx context.Context, logger *slog.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
 	return fmt.Errorf("convert PDF to '%+v' with pdfcpu: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadMetadata is not available in this implementation.
-func (engine *PdfCpu) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error) {
+func (engine *PdfCpu) ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error) {
 	return nil, fmt.Errorf("read PDF metadata with pdfcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // WriteMetadata is not available in this implementation.
-func (engine *PdfCpu) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error {
+func (engine *PdfCpu) WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error {
 	return fmt.Errorf("write PDF metadata with pdfcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // PageCount is not available in this implementation.
-func (engine *PdfCpu) PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error) {
+func (engine *PdfCpu) PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error) {
 	return 0, fmt.Errorf("page count with pdfcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadBookmarks reads the document outline (bookmarks) of a PDF file using pdfcpu.
-func (engine *PdfCpu) ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
+func (engine *PdfCpu) ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
 	tmpPath := fmt.Sprintf("%s.read.json", inputPath)
 	args := []string{"bookmarks", "export", inputPath, tmpPath}
 	cmd, err := gotenberg.CommandContext(ctx, logger, engine.binPath, args...)
@@ -201,7 +200,7 @@ func (engine *PdfCpu) ReadBookmarks(ctx context.Context, logger *zap.Logger, inp
 	defer func() {
 		err := os.Remove(tmpPath)
 		if err != nil && !os.IsNotExist(err) {
-			logger.Error(fmt.Sprintf("remove temporary bookmarks JSON file: %v", err))
+			logger.ErrorContext(ctx, fmt.Sprintf("remove temporary bookmarks JSON file: %v", err))
 		}
 	}()
 
@@ -269,7 +268,7 @@ func (engine *PdfCpu) ReadBookmarks(ctx context.Context, logger *zap.Logger, inp
 }
 
 // WriteBookmarks adds a document outline (bookmarks) to a PDF file using pdfcpu.
-func (engine *PdfCpu) WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
+func (engine *PdfCpu) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
 	if len(bookmarks) == 0 {
 		return nil
 	}
@@ -305,7 +304,7 @@ func (engine *PdfCpu) WriteBookmarks(ctx context.Context, logger *zap.Logger, in
 	defer func() {
 		err := os.Remove(tmpPath)
 		if err != nil {
-			logger.Error(fmt.Sprintf("remove temporary bookmarks JSON file: %v", err))
+			logger.ErrorContext(ctx, fmt.Sprintf("remove temporary bookmarks JSON file: %v", err))
 		}
 	}()
 
@@ -325,12 +324,12 @@ func (engine *PdfCpu) WriteBookmarks(ctx context.Context, logger *zap.Logger, in
 
 // EmbedFiles embeds files into a PDF. All files are embedded as file attachments
 // without modifying the main PDF content.
-func (engine *PdfCpu) EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error {
+func (engine *PdfCpu) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {
 	if len(filePaths) == 0 {
 		return nil
 	}
 
-	logger.Debug(fmt.Sprintf("embedding %d file(s) to %s: %v", len(filePaths), inputPath, filePaths))
+	logger.DebugContext(ctx, fmt.Sprintf("embedding %d file(s) to %s: %v", len(filePaths), inputPath, filePaths))
 
 	args := make([]string, 0, 3+len(filePaths))
 	args = append(args, "attachments", "add", inputPath)
@@ -350,7 +349,7 @@ func (engine *PdfCpu) EmbedFiles(ctx context.Context, logger *zap.Logger, filePa
 }
 
 // Encrypt adds password protection to a PDF file using pdfcpu.
-func (engine *PdfCpu) Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error {
+func (engine *PdfCpu) Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error {
 	if userPassword == "" {
 		return errors.New("user password cannot be empty")
 	}
@@ -381,17 +380,17 @@ func (engine *PdfCpu) Encrypt(ctx context.Context, logger *zap.Logger, inputPath
 }
 
 // Watermark applies a watermark (behind page content) to a PDF file using pdfcpu.
-func (engine *PdfCpu) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *PdfCpu) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return engine.applyStampOrWatermark(ctx, logger, "watermark", inputPath, stamp)
 }
 
 // Stamp applies a stamp (on top of page content) to a PDF file using pdfcpu.
-func (engine *PdfCpu) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *PdfCpu) Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return engine.applyStampOrWatermark(ctx, logger, "stamp", inputPath, stamp)
 }
 
 // Rotate rotates pages of a PDF file by the given angle using pdfcpu.
-func (engine *PdfCpu) Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error {
+func (engine *PdfCpu) Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error {
 	args := []string{"rotate"}
 	if pages != "" {
 		args = append(args, "-pages", pages)
@@ -411,7 +410,7 @@ func (engine *PdfCpu) Rotate(ctx context.Context, logger *zap.Logger, inputPath
 	return nil
 }
 
-func (engine *PdfCpu) applyStampOrWatermark(ctx context.Context, logger *zap.Logger, command string, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *PdfCpu) applyStampOrWatermark(ctx context.Context, logger *slog.Logger, command string, inputPath string, stamp gotenberg.Stamp) error {
 	var mode string
 	switch stamp.Source {
 	case gotenberg.StampSourceText:

pkg/modules/pdfengines/multi.go

@@ -3,10 +3,12 @@ package pdfengines
 import (
 	"context"
 	"fmt"
+	"log/slog"
 	"sync"
 
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace"
 	"go.uber.org/multierr"
-	"go.uber.org/zap"
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
@@ -61,7 +63,13 @@ func newMultiPdfEngines(
 
 // Merge combines multiple PDF files into a single document using the first
 // available engine that supports PDF merging.
-func (multi *multiPdfEngines) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+//
+//nolint:dupl
+func (multi *multiPdfEngines) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Merge", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -74,6 +82,7 @@ func (multi *multiPdfEngines) Merge(ctx context.Context, logger *zap.Logger, inp
 		case mergeErr := <-errChan:
 			errored := multierr.AppendInto(&err, mergeErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -81,7 +90,11 @@ func (multi *multiPdfEngines) Merge(ctx context.Context, logger *zap.Logger, inp
 		}
 	}
 
-	return fmt.Errorf("merge PDFs with multi PDF engines: %w", err)
+	err = fmt.Errorf("merge PDFs with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 type splitResult struct {
@@ -91,7 +104,11 @@ type splitResult struct {
 
 // Split divides the PDF into separate pages using the first available engine
 // that supports PDF splitting.
-func (multi *multiPdfEngines) Split(ctx context.Context, logger *zap.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
+func (multi *multiPdfEngines) Split(ctx context.Context, logger *slog.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Split", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	var mu sync.Mutex // to safely append errors.
 
@@ -110,6 +127,7 @@ func (multi *multiPdfEngines) Split(ctx context.Context, logger *zap.Logger, mod
 				err = multierr.Append(err, result.err)
 				mu.Unlock()
 			} else {
+				span.SetStatus(codes.Ok, "")
 				return result.outputPaths, nil
 			}
 		case <-ctx.Done():
@@ -117,12 +135,20 @@ func (multi *multiPdfEngines) Split(ctx context.Context, logger *zap.Logger, mod
 		}
 	}
 
-	return nil, fmt.Errorf("split PDF with multi PDF engines: %w", err)
+	err = fmt.Errorf("split PDF with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return nil, err
 }
 
 // Flatten merges existing annotation appearances with page content using the
 // first available engine that supports flattening.
-func (multi *multiPdfEngines) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
+func (multi *multiPdfEngines) Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Flatten", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -135,6 +161,7 @@ func (multi *multiPdfEngines) Flatten(ctx context.Context, logger *zap.Logger, i
 		case mergeErr := <-errChan:
 			errored := multierr.AppendInto(&err, mergeErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -142,12 +169,20 @@ func (multi *multiPdfEngines) Flatten(ctx context.Context, logger *zap.Logger, i
 		}
 	}
 
-	return fmt.Errorf("flatten PDF with multi PDF engines: %w", err)
+	err = fmt.Errorf("flatten PDF with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 // Convert transforms the given PDF to a specific PDF format using the first
 // available engine that supports PDF conversion.
-func (multi *multiPdfEngines) Convert(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+func (multi *multiPdfEngines) Convert(ctx context.Context, logger *slog.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Convert", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -160,6 +195,7 @@ func (multi *multiPdfEngines) Convert(ctx context.Context, logger *zap.Logger, f
 		case mergeErr := <-errChan:
 			errored := multierr.AppendInto(&err, mergeErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -167,7 +203,11 @@ func (multi *multiPdfEngines) Convert(ctx context.Context, logger *zap.Logger, f
 		}
 	}
 
-	return fmt.Errorf("convert PDF to '%+v' with multi PDF engines: %w", formats, err)
+	err = fmt.Errorf("convert PDF to '%+v' with multi PDF engines: %w", formats, err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 type readMetadataResult struct {
@@ -177,7 +217,13 @@ type readMetadataResult struct {
 
 // ReadMetadata extracts metadata from a PDF file using the first available
 // engine that supports metadata reading.
-func (multi *multiPdfEngines) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error) {
+//
+//nolint:dupl
+func (multi *multiPdfEngines) ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error) {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.ReadMetadata", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	var mu sync.Mutex // to safely append errors.
 
@@ -196,6 +242,7 @@ func (multi *multiPdfEngines) ReadMetadata(ctx context.Context, logger *zap.Logg
 				err = multierr.Append(err, result.err)
 				mu.Unlock()
 			} else {
+				span.SetStatus(codes.Ok, "")
 				return result.metadata, nil
 			}
 		case <-ctx.Done():
@@ -203,12 +250,20 @@ func (multi *multiPdfEngines) ReadMetadata(ctx context.Context, logger *zap.Logg
 		}
 	}
 
-	return nil, fmt.Errorf("read PDF metadata with multi PDF engines: %w", err)
+	err = fmt.Errorf("read PDF metadata with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return nil, err
 }
 
 // WriteMetadata embeds metadata into a PDF file using the first available
 // engine that supports metadata writing.
-func (multi *multiPdfEngines) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error {
+func (multi *multiPdfEngines) WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.WriteMetadata", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -221,6 +276,7 @@ func (multi *multiPdfEngines) WriteMetadata(ctx context.Context, logger *zap.Log
 		case writeMetadataErr := <-errChan:
 			errored := multierr.AppendInto(&err, writeMetadataErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -228,7 +284,11 @@ func (multi *multiPdfEngines) WriteMetadata(ctx context.Context, logger *zap.Log
 		}
 	}
 
-	return fmt.Errorf("write PDF metadata with multi PDF engines: %w", err)
+	err = fmt.Errorf("write PDF metadata with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 type pageCountResult struct {
@@ -238,7 +298,11 @@ type pageCountResult struct {
 
 // PageCount returns the number of pages in a PDF file using the first available
 // engine that supports metadata reading.
-func (multi *multiPdfEngines) PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error) {
+func (multi *multiPdfEngines) PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error) {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.PageCount", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	var mu sync.Mutex // to safely append errors.
 
@@ -257,6 +321,7 @@ func (multi *multiPdfEngines) PageCount(ctx context.Context, logger *zap.Logger,
 				err = multierr.Append(err, result.err)
 				mu.Unlock()
 			} else {
+				span.SetStatus(codes.Ok, "")
 				return result.pageCount, nil
 			}
 		case <-ctx.Done():
@@ -264,7 +329,11 @@ func (multi *multiPdfEngines) PageCount(ctx context.Context, logger *zap.Logger,
 		}
 	}
 
-	return 0, fmt.Errorf("page count with multi PDF engines: %w", err)
+	err = fmt.Errorf("page count with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return 0, err
 }
 
 type readBookmarksResult struct {
@@ -274,7 +343,13 @@ type readBookmarksResult struct {
 
 // ReadBookmarks reads bookmarks from a PDF file using the first available
 // engine that supports bookmarks reading.
-func (multi *multiPdfEngines) ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
+//
+//nolint:dupl
+func (multi *multiPdfEngines) ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.ReadBookmarks", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	var mu sync.Mutex // to safely append errors.
 
@@ -293,6 +368,7 @@ func (multi *multiPdfEngines) ReadBookmarks(ctx context.Context, logger *zap.Log
 				err = multierr.Append(err, result.err)
 				mu.Unlock()
 			} else {
+				span.SetStatus(codes.Ok, "")
 				return result.bookmarks, nil
 			}
 		case <-ctx.Done():
@@ -300,12 +376,20 @@ func (multi *multiPdfEngines) ReadBookmarks(ctx context.Context, logger *zap.Log
 		}
 	}
 
-	return nil, fmt.Errorf("read PDF bookmarks with multi PDF engines: %w", err)
+	err = fmt.Errorf("read PDF bookmarks with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return nil, err
 }
 
 // WriteBookmarks adds a document outline (bookmarks) to a PDF file using the
 // first available engine that supports bookmarks writing.
-func (multi *multiPdfEngines) WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
+func (multi *multiPdfEngines) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.WriteBookmarks", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -318,6 +402,7 @@ func (multi *multiPdfEngines) WriteBookmarks(ctx context.Context, logger *zap.Lo
 		case writeBookmarksErr := <-errChan:
 			errored := multierr.AppendInto(&err, writeBookmarksErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -325,12 +410,20 @@ func (multi *multiPdfEngines) WriteBookmarks(ctx context.Context, logger *zap.Lo
 		}
 	}
 
-	return fmt.Errorf("write PDF bookmarks with multi PDF engines: %w", err)
+	err = fmt.Errorf("write PDF bookmarks with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 // Encrypt adds password protection to a PDF file using the first available
 // engine that supports password protection.
-func (multi *multiPdfEngines) Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error {
+func (multi *multiPdfEngines) Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Encrypt", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -343,6 +436,7 @@ func (multi *multiPdfEngines) Encrypt(ctx context.Context, logger *zap.Logger, i
 		case protectErr := <-errChan:
 			errored := multierr.AppendInto(&err, protectErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -350,12 +444,22 @@ func (multi *multiPdfEngines) Encrypt(ctx context.Context, logger *zap.Logger, i
 		}
 	}
 
-	return fmt.Errorf("encrypt PDF using multi PDF engines: %w", err)
+	err = fmt.Errorf("encrypt PDF using multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 // EmbedFiles embeds files into a PDF using the first available
 // engine that supports file embedding.
-func (multi *multiPdfEngines) EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error {
+//
+//nolint:dupl
+func (multi *multiPdfEngines) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.EmbedFiles", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -368,6 +472,7 @@ func (multi *multiPdfEngines) EmbedFiles(ctx context.Context, logger *zap.Logger
 		case embedErr := <-errChan:
 			errored := multierr.AppendInto(&err, embedErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -375,12 +480,22 @@ func (multi *multiPdfEngines) EmbedFiles(ctx context.Context, logger *zap.Logger
 		}
 	}
 
-	return fmt.Errorf("embed files into PDF using multi PDF engines: %w", err)
+	err = fmt.Errorf("embed files into PDF using multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 // Watermark applies a watermark (behind page content) to a PDF file using the
 // first available engine that supports watermarking.
-func (multi *multiPdfEngines) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+//
+//nolint:dupl
+func (multi *multiPdfEngines) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Watermark", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -393,6 +508,7 @@ func (multi *multiPdfEngines) Watermark(ctx context.Context, logger *zap.Logger,
 		case watermarkErr := <-errChan:
 			errored := multierr.AppendInto(&err, watermarkErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -400,12 +516,22 @@ func (multi *multiPdfEngines) Watermark(ctx context.Context, logger *zap.Logger,
 		}
 	}
 
-	return fmt.Errorf("watermark PDF with multi PDF engines: %w", err)
+	err = fmt.Errorf("watermark PDF with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 // Stamp applies a stamp (on top of page content) to a PDF file using the
 // first available engine that supports stamping.
-func (multi *multiPdfEngines) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+//
+//nolint:dupl
+func (multi *multiPdfEngines) Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Stamp", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -418,6 +544,7 @@ func (multi *multiPdfEngines) Stamp(ctx context.Context, logger *zap.Logger, inp
 		case stampErr := <-errChan:
 			errored := multierr.AppendInto(&err, stampErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -425,12 +552,20 @@ func (multi *multiPdfEngines) Stamp(ctx context.Context, logger *zap.Logger, inp
 		}
 	}
 
-	return fmt.Errorf("stamp PDF with multi PDF engines: %w", err)
+	err = fmt.Errorf("stamp PDF with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 // Rotate rotates pages of a PDF file using the first available engine that
 // supports rotation.
-func (multi *multiPdfEngines) Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error {
+func (multi *multiPdfEngines) Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.Rotate", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
 	var err error
 	errChan := make(chan error, 1)
 
@@ -443,6 +578,7 @@ func (multi *multiPdfEngines) Rotate(ctx context.Context, logger *zap.Logger, in
 		case rotateErr := <-errChan:
 			errored := multierr.AppendInto(&err, rotateErr)
 			if !errored {
+				span.SetStatus(codes.Ok, "")
 				return nil
 			}
 		case <-ctx.Done():
@@ -450,7 +586,11 @@ func (multi *multiPdfEngines) Rotate(ctx context.Context, logger *zap.Logger, in
 		}
 	}
 
-	return fmt.Errorf("rotate PDF with multi PDF engines: %w", err)
+	err = fmt.Errorf("rotate PDF with multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
 }
 
 // Interface guards.

pkg/modules/pdfengines/pdfengines.go

@@ -115,12 +115,12 @@ func (mod *PdfEngines) Provision(ctx *gotenberg.Context) error {
 	}
 
 	// Example in the case of deprecated module name.
-	//for i, name := range defaultNames {
-	//	if name == "unoconv-pdfengine" || name == "uno-pdfengine" {
-	//		logger.Warn(fmt.Sprintf("%s is deprecated; prefer libreoffice-pdfengine instead", name))
-	//		mod.defaultNames[i] = "libreoffice-pdfengine"
-	//	}
-	//}
+	// for i, name := range defaultNames {
+	// 	if name == "unoconv-pdfengine" || name == "uno-pdfengine" {
+	// 		logger.Warn(fmt.Sprintf("%s is deprecated; prefer libreoffice-pdfengine instead", name))
+	// 		mod.defaultNames[i] = "libreoffice-pdfengine"
+	// 	}
+	// }
 
 	mod.mergeNames = defaultNames
 	if len(mergeNames) > 0 {
@@ -253,19 +253,19 @@ func (mod *PdfEngines) Validate() error {
 // modules.
 func (mod *PdfEngines) SystemMessages() []string {
 	return []string{
-		fmt.Sprintf("merge engines - %s", strings.Join(mod.mergeNames[:], " ")),
-		fmt.Sprintf("split engines - %s", strings.Join(mod.splitNames[:], " ")),
-		fmt.Sprintf("flatten engines - %s", strings.Join(mod.flattenNames[:], " ")),
-		fmt.Sprintf("convert engines - %s", strings.Join(mod.convertNames[:], " ")),
-		fmt.Sprintf("read metadata engines - %s", strings.Join(mod.readMetadataNames[:], " ")),
-		fmt.Sprintf("write metadata engines - %s", strings.Join(mod.writeMetadataNames[:], " ")),
-		fmt.Sprintf("encrypt engines - %s", strings.Join(mod.encryptNames[:], " ")),
-		fmt.Sprintf("embed engines - %s", strings.Join(mod.embedNames[:], " ")),
-		fmt.Sprintf("read bookmarks engines - %s", strings.Join(mod.readBookmarksNames[:], " ")),
-		fmt.Sprintf("write bookmarks engines - %s", strings.Join(mod.writeBookmarksNames[:], " ")),
-		fmt.Sprintf("watermark engines - %s", strings.Join(mod.watermarkNames[:], " ")),
-		fmt.Sprintf("stamp engines - %s", strings.Join(mod.stampNames[:], " ")),
-		fmt.Sprintf("rotate engines - %s", strings.Join(mod.rotateNames[:], " ")),
+		fmt.Sprintf("merge engines - %s", strings.Join(mod.mergeNames, " ")),
+		fmt.Sprintf("split engines - %s", strings.Join(mod.splitNames, " ")),
+		fmt.Sprintf("flatten engines - %s", strings.Join(mod.flattenNames, " ")),
+		fmt.Sprintf("convert engines - %s", strings.Join(mod.convertNames, " ")),
+		fmt.Sprintf("read metadata engines - %s", strings.Join(mod.readMetadataNames, " ")),
+		fmt.Sprintf("write metadata engines - %s", strings.Join(mod.writeMetadataNames, " ")),
+		fmt.Sprintf("encrypt engines - %s", strings.Join(mod.encryptNames, " ")),
+		fmt.Sprintf("embed engines - %s", strings.Join(mod.embedNames, " ")),
+		fmt.Sprintf("read bookmarks engines - %s", strings.Join(mod.readBookmarksNames, " ")),
+		fmt.Sprintf("write bookmarks engines - %s", strings.Join(mod.writeBookmarksNames, " ")),
+		fmt.Sprintf("watermark engines - %s", strings.Join(mod.watermarkNames, " ")),
+		fmt.Sprintf("stamp engines - %s", strings.Join(mod.stampNames, " ")),
+		fmt.Sprintf("rotate engines - %s", strings.Join(mod.rotateNames, " ")),
 	}
 }
 

pkg/modules/pdftk/pdftk.go

@@ -5,13 +5,12 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"syscall"
 
-	"go.uber.org/zap"
-
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
@@ -79,7 +78,7 @@ func (engine *PdfTk) Debug() map[string]any {
 }
 
 // Split splits a given PDF file.
-func (engine *PdfTk) Split(ctx context.Context, logger *zap.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
+func (engine *PdfTk) Split(ctx context.Context, logger *slog.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
 	var args []string
 	outputPath := fmt.Sprintf("%s/%s", outputDirPath, filepath.Base(inputPath))
 
@@ -107,7 +106,7 @@ func (engine *PdfTk) Split(ctx context.Context, logger *zap.Logger, mode gotenbe
 }
 
 // Merge combines multiple PDFs into a single PDF.
-func (engine *PdfTk) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+func (engine *PdfTk) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
 	args := make([]string, 0, 3+len(inputPaths))
 	args = append(args, inputPaths...)
 	args = append(args, "cat", "output", outputPath)
@@ -126,42 +125,42 @@ func (engine *PdfTk) Merge(ctx context.Context, logger *zap.Logger, inputPaths [
 }
 
 // Flatten is not available in this implementation.
-func (engine *PdfTk) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
+func (engine *PdfTk) Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error {
 	return fmt.Errorf("flatten PDF with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Convert is not available in this implementation.
-func (engine *PdfTk) Convert(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+func (engine *PdfTk) Convert(ctx context.Context, logger *slog.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
 	return fmt.Errorf("convert PDF to '%+v' with PDFtk: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadMetadata is not available in this implementation.
-func (engine *PdfTk) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error) {
+func (engine *PdfTk) ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error) {
 	return nil, fmt.Errorf("read PDF metadata with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // WriteMetadata is not available in this implementation.
-func (engine *PdfTk) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error {
+func (engine *PdfTk) WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error {
 	return fmt.Errorf("write PDF metadata with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // PageCount is not available in this implementation.
-func (engine *PdfTk) PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error) {
+func (engine *PdfTk) PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error) {
 	return 0, fmt.Errorf("page count with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // WriteBookmarks is not available in this implementation.
-func (engine *PdfTk) WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
+func (engine *PdfTk) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
 	return fmt.Errorf("write PDF bookmarks with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadBookmarks is not available in this implementation.
-func (engine *PdfTk) ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
+func (engine *PdfTk) ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
 	return nil, fmt.Errorf("read PDF bookmarks with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Encrypt adds password protection to a PDF file using PDFtk.
-func (engine *PdfTk) Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error {
+func (engine *PdfTk) Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error {
 	if userPassword == "" {
 		return errors.New("user password cannot be empty")
 	}
@@ -199,13 +198,13 @@ func (engine *PdfTk) Encrypt(ctx context.Context, logger *zap.Logger, inputPath,
 }
 
 // EmbedFiles is not available in this implementation.
-func (engine *PdfTk) EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error {
+func (engine *PdfTk) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {
 	return fmt.Errorf("embed files with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Watermark applies a watermark (behind page content) to a PDF file using PDFtk.
 // Only PDF source is supported.
-func (engine *PdfTk) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *PdfTk) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	if stamp.Source != gotenberg.StampSourcePDF {
 		return fmt.Errorf("watermark PDF with PDFtk: %w", gotenberg.ErrPdfStampSourceNotSupported)
 	}
@@ -234,7 +233,7 @@ func (engine *PdfTk) Watermark(ctx context.Context, logger *zap.Logger, inputPat
 
 // Stamp applies a stamp (on top of page content) to a PDF file using PDFtk.
 // Only PDF source is supported.
-func (engine *PdfTk) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *PdfTk) Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	if stamp.Source != gotenberg.StampSourcePDF {
 		return fmt.Errorf("stamp PDF with PDFtk: %w", gotenberg.ErrPdfStampSourceNotSupported)
 	}
@@ -264,7 +263,7 @@ func (engine *PdfTk) Stamp(ctx context.Context, logger *zap.Logger, inputPath st
 // Rotate rotates all pages of a PDF file by the given angle using PDFtk.
 // Page-specific rotation is not supported; if pages is non-empty,
 // ErrPdfEngineMethodNotSupported is returned.
-func (engine *PdfTk) Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error {
+func (engine *PdfTk) Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error {
 	if pages != "" {
 		return fmt.Errorf("rotate PDF with PDFtk (page-specific rotation): %w", gotenberg.ErrPdfEngineMethodNotSupported)
 	}

pkg/modules/prometheus/prometheus.go

@@ -177,9 +177,9 @@ func (mod *Prometheus) Routes() ([]api.Route, error) {
 
 	return []api.Route{
 		{
-			Method:         http.MethodGet,
-			Path:           mod.metricsPath,
-			DisableLogging: mod.disableRouteLogging,
+			Method:           http.MethodGet,
+			Path:             mod.metricsPath,
+			DisableTelemetry: mod.disableRouteLogging,
 			Handler: echo.WrapHandler(
 				promhttp.HandlerFor(mod.registry, promhttp.HandlerOpts{}),
 			),

pkg/modules/qpdf/qpdf.go

@@ -5,13 +5,12 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"syscall"
 
-	"go.uber.org/zap"
-
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
@@ -82,7 +81,7 @@ func (engine *QPdf) Debug() map[string]any {
 }
 
 // Split splits a given PDF file.
-func (engine *QPdf) Split(ctx context.Context, logger *zap.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
+func (engine *QPdf) Split(ctx context.Context, logger *slog.Logger, mode gotenberg.SplitMode, inputPath, outputDirPath string) ([]string, error) {
 	var args []string
 	outputPath := fmt.Sprintf("%s/%s", outputDirPath, filepath.Base(inputPath))
 
@@ -113,7 +112,7 @@ func (engine *QPdf) Split(ctx context.Context, logger *zap.Logger, mode gotenber
 }
 
 // Merge combines multiple PDFs into a single PDF.
-func (engine *QPdf) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+func (engine *QPdf) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
 	args := make([]string, 0, 4+len(engine.globalArgs)+len(inputPaths))
 	args = append(args, "--empty")
 	args = append(args, engine.globalArgs...)
@@ -136,7 +135,7 @@ func (engine *QPdf) Merge(ctx context.Context, logger *zap.Logger, inputPaths []
 
 // Flatten merges annotation appearances with page content, deleting the
 // original annotations.
-func (engine *QPdf) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
+func (engine *QPdf) Flatten(ctx context.Context, logger *slog.Logger, inputPath string) error {
 	args := make([]string, 0, 4+len(engine.globalArgs))
 	args = append(args, inputPath)
 	args = append(args, "--generate-appearances")
@@ -158,37 +157,37 @@ func (engine *QPdf) Flatten(ctx context.Context, logger *zap.Logger, inputPath s
 }
 
 // Convert is not available in this implementation.
-func (engine *QPdf) Convert(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+func (engine *QPdf) Convert(ctx context.Context, logger *slog.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
 	return fmt.Errorf("convert PDF to '%+v' with QPDF: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadMetadata is not available in this implementation.
-func (engine *QPdf) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]any, error) {
+func (engine *QPdf) ReadMetadata(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error) {
 	return nil, fmt.Errorf("read PDF metadata with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // WriteMetadata is not available in this implementation.
-func (engine *QPdf) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]any, inputPath string) error {
+func (engine *QPdf) WriteMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error {
 	return fmt.Errorf("write PDF metadata with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // PageCount is not available in this implementation.
-func (engine *QPdf) PageCount(ctx context.Context, logger *zap.Logger, inputPath string) (int, error) {
+func (engine *QPdf) PageCount(ctx context.Context, logger *slog.Logger, inputPath string) (int, error) {
 	return 0, fmt.Errorf("page count with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // WriteBookmarks is not available in this implementation.
-func (engine *QPdf) WriteBookmarks(ctx context.Context, logger *zap.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
+func (engine *QPdf) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []gotenberg.Bookmark) error {
 	return fmt.Errorf("write PDF bookmarks with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // ReadBookmarks is not available in this implementation.
-func (engine *QPdf) ReadBookmarks(ctx context.Context, logger *zap.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
+func (engine *QPdf) ReadBookmarks(ctx context.Context, logger *slog.Logger, inputPath string) ([]gotenberg.Bookmark, error) {
 	return nil, fmt.Errorf("read PDF bookmarks with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Encrypt adds password protection to a PDF file using QPDF.
-func (engine *QPdf) Encrypt(ctx context.Context, logger *zap.Logger, inputPath, userPassword, ownerPassword string) error {
+func (engine *QPdf) Encrypt(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error {
 	if userPassword == "" {
 		return errors.New("user password cannot be empty")
 	}
@@ -217,22 +216,22 @@ func (engine *QPdf) Encrypt(ctx context.Context, logger *zap.Logger, inputPath,
 }
 
 // EmbedFiles is not available in this implementation.
-func (engine *QPdf) EmbedFiles(ctx context.Context, logger *zap.Logger, filePaths []string, inputPath string) error {
+func (engine *QPdf) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {
 	return fmt.Errorf("embed files with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Watermark is not available in this implementation.
-func (engine *QPdf) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *QPdf) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return fmt.Errorf("watermark PDF with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Stamp is not available in this implementation.
-func (engine *QPdf) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+func (engine *QPdf) Stamp(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return fmt.Errorf("stamp PDF with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
 // Rotate is not available in this implementation.
-func (engine *QPdf) Rotate(ctx context.Context, logger *zap.Logger, inputPath string, angle int, pages string) error {
+func (engine *QPdf) Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error {
 	return fmt.Errorf("rotate PDF with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 

pkg/modules/webhook/client.go

@@ -1,15 +1,22 @@
 package webhook
 
 import (
+	"context"
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
 	"strconv"
 	"time"
 
 	"github.com/hashicorp/go-retryablehttp"
 	"github.com/labstack/echo/v4"
-	"go.uber.org/zap"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/trace"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
 // client gathers all the data required to send a request to a webhook.
@@ -22,11 +29,11 @@ type client struct {
 	startTime        time.Time
 
 	client *retryablehttp.Client
-	logger *zap.Logger
+	logger *slog.Logger
 }
 
 // send call the webhook either to send the success response or the error response.
-func (c client) send(body io.Reader, headers map[string]string, errored bool) error {
+func (c client) send(ctx context.Context, body io.Reader, headers map[string]string, errored bool) error {
 	url := c.url
 	if errored {
 		url = c.errorUrl
@@ -37,11 +44,25 @@ func (c client) send(body io.Reader, headers map[string]string, errored bool) er
 		method = c.errorMethod
 	}
 
+	spanName := fmt.Sprintf("%s Webhook", method)
+	if errored {
+		spanName = fmt.Sprintf("%s Webhook Error", method)
+	}
+
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, spanName, trace.WithSpanKind(trace.SpanKindClient))
+	defer span.End()
+
 	req, err := retryablehttp.NewRequest(method, url, body)
 	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
 		return fmt.Errorf("create '%s' request to '%s': %w", method, url, err)
 	}
 
+	// Inject trace context into outbound request headers.
+	otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(req.Header))
+
 	req.Header.Set("User-Agent", "Gotenberg")
 
 	// Extra HTTP headers are the custom headers from the user.
@@ -63,6 +84,8 @@ func (c client) send(body io.Reader, headers map[string]string, errored bool) er
 
 		bodySize, err := strconv.ParseInt(contentLength, 10, 64)
 		if err != nil {
+			span.RecordError(err)
+			span.SetStatus(codes.Error, err.Error())
 			return fmt.Errorf("parse content length entry: %w", err)
 		}
 
@@ -75,17 +98,22 @@ func (c client) send(body io.Reader, headers map[string]string, errored bool) er
 
 	resp, err := c.client.Do(req)
 	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
 		return fmt.Errorf("send '%s' request to '%s': %w", method, url, err)
 	}
 
 	if resp.StatusCode >= http.StatusBadRequest {
-		return fmt.Errorf("send '%s' request to '%s': got status: '%s'", method, url, resp.Status)
+		err := fmt.Errorf("send '%s' request to '%s': got status: '%s'", method, url, resp.Status)
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
 	}
 
 	defer func() {
 		err := resp.Body.Close()
 		if err != nil {
-			c.logger.Error(fmt.Sprintf("close response body from '%s': %s", url, err))
+			c.logger.ErrorContext(ctx, fmt.Sprintf("close response body from '%s': %s", url, err))
 		}
 	}()
 
@@ -93,20 +121,22 @@ func (c client) send(body io.Reader, headers map[string]string, errored bool) er
 	finishTime := time.Now()
 
 	// Now let's log!
-	fields := make([]zap.Field, 5)
-	fields[0] = zap.String("webhook_url", url)
-	fields[1] = zap.String("method", method)
-	fields[2] = zap.Int64("latency", int64(finishTime.Sub(c.startTime)))
-	fields[3] = zap.String("latency_human", finishTime.Sub(c.startTime).String())
-	fields[4] = zap.Int64("bytes_out", req.ContentLength)
+	attrs := []any{
+		slog.String("webhook_url", url),
+		slog.String("method", method),
+		slog.Int64("latency", int64(finishTime.Sub(c.startTime))),
+		slog.String("latency_human", finishTime.Sub(c.startTime).String()),
+		slog.Int64("bytes_out", req.ContentLength),
+	}
 
 	if errored {
-		c.logger.Warn("request to webhook with error details handled", fields...)
-
+		c.logger.WarnContext(ctx, "request to webhook with error details handled", attrs...)
+		span.SetStatus(codes.Ok, "")
 		return nil
 	}
 
-	c.logger.Info("request to webhook handled", fields...)
+	c.logger.InfoContext(ctx, "request to webhook handled", attrs...)
+	span.SetStatus(codes.Ok, "")
 
 	return nil
 }

pkg/modules/webhook/middleware.go

@@ -21,13 +21,13 @@ import (
 )
 
 type sendOutputFileParams struct {
-	ctx              *api.Context
-	outputPath       string
-	extraHttpHeaders map[string]string
-	traceHeader      string
-	trace            string
-	client           *client
-	handleError      func(error)
+	ctx                 *api.Context
+	outputPath          string
+	extraHttpHeaders    map[string]string
+	correlationIdHeader string
+	correlationId       string
+	client              *client
+	handleError         func(error)
 }
 
 func webhookMiddleware(w *Webhook) api.Middleware {
@@ -72,16 +72,16 @@ func webhookMiddleware(w *Webhook) api.Middleware {
 					}
 
 					headers := map[string]string{
-						echo.HeaderContentType:   http.DetectContentType(fileHeader),
-						echo.HeaderContentLength: strconv.FormatInt(fileStat.Size(), 10),
-						params.traceHeader:       params.trace,
+						echo.HeaderContentType:     http.DetectContentType(fileHeader),
+						echo.HeaderContentLength:   strconv.FormatInt(fileStat.Size(), 10),
+						params.correlationIdHeader: params.correlationId,
 					}
 					_, ok := params.extraHttpHeaders[echo.HeaderContentDisposition]
 					if !ok {
 						headers[echo.HeaderContentDisposition] = fmt.Sprintf("attachment; filename=%q", params.ctx.OutputFilename(params.outputPath))
 					}
 
-					err = params.client.send(bufio.NewReader(outputFile), headers, false)
+					err = params.client.send(params.ctx, bufio.NewReader(outputFile), headers, false)
 					if err != nil {
 						params.ctx.Log().Error(fmt.Sprintf("send output file to webhook: %s", err))
 						params.handleError(err)
@@ -179,8 +179,8 @@ func webhookMiddleware(w *Webhook) api.Middleware {
 					// Retrieve values from echo.Context before it gets recycled.
 					// See https://github.com/gotenberg/gotenberg/issues/1000.
 					startTime := c.Get("startTime").(time.Time)
-					traceHeader := c.Get("traceHeader").(string)
-					trace := c.Get("trace").(string)
+					correlationIdHeader := c.Get("correlationIdHeader").(string)
+					correlationId := c.Get("correlationId").(string)
 
 					client := &client{
 						url:              webhookUrl,
@@ -226,10 +226,10 @@ func webhookMiddleware(w *Webhook) api.Middleware {
 
 						headers := map[string]string{
 							echo.HeaderContentType: echo.MIMEApplicationJSON,
-							traceHeader:            trace,
+							correlationIdHeader:    correlationId,
 						}
 
-						err = client.send(bytes.NewReader(b), headers, true)
+						err = client.send(ctx, bytes.NewReader(b), headers, true)
 						if err != nil {
 							ctx.Log().Error(fmt.Sprintf("send error response to webhook: %s", err.Error()))
 						}
@@ -262,13 +262,13 @@ func webhookMiddleware(w *Webhook) api.Middleware {
 						}
 						// No error, let's send the output file to the webhook URL.
 						sendOutputFile(sendOutputFileParams{
-							ctx:              ctx,
-							outputPath:       outputPath,
-							extraHttpHeaders: extraHttpHeaders,
-							traceHeader:      traceHeader,
-							trace:            trace,
-							client:           client,
-							handleError:      handleError,
+							ctx:                 ctx,
+							outputPath:          outputPath,
+							extraHttpHeaders:    extraHttpHeaders,
+							correlationIdHeader: correlationIdHeader,
+							correlationId:       correlationId,
+							client:              client,
+							handleError:         handleError,
 						})
 						return c.NoContent(http.StatusNoContent)
 					}
@@ -332,13 +332,13 @@ func webhookMiddleware(w *Webhook) api.Middleware {
 						}
 
 						sendOutputFile(sendOutputFileParams{
-							ctx:              ctx,
-							outputPath:       outputPath,
-							extraHttpHeaders: extraHttpHeaders,
-							traceHeader:      traceHeader,
-							trace:            trace,
-							client:           client,
-							handleError:      handleError,
+							ctx:                 ctx,
+							outputPath:          outputPath,
+							extraHttpHeaders:    extraHttpHeaders,
+							correlationIdHeader: correlationIdHeader,
+							correlationId:       correlationId,
+							client:              client,
+							handleError:         handleError,
 						})
 					}()
 

pkg/standard/imports.go

@@ -8,7 +8,6 @@ import (
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice/api"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice/pdfengine"
-	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/logging"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/pdfcpu"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/pdfengines"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/pdftk"