feat(otel): add OpenTelemetry support

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