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

@@ -0,0 +1,40 @@
+package log
+
+import (
+	"fmt"
+	"log/slog"
+)
+
+// Foreground colors.
+// Copy pasted from go.uber.org/zap/internal/color/color.go
+const (
+	black color = iota + 30
+	red
+	green
+	yellow
+	blue
+	magenta
+	cyan
+	white
+)
+
+type color uint8
+
+func (c color) Add(s string) string {
+	return fmt.Sprintf("\x1b[%dm%s\x1b[0m", uint8(c), s)
+}
+
+func levelToColor(l slog.Level) color {
+	switch l {
+	case slog.LevelDebug:
+		return cyan
+	case slog.LevelInfo:
+		return blue
+	case slog.LevelWarn:
+		return yellow
+	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)
+)