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pkg/telemetry/otel.go

@@ -0,0 +1,97 @@
+package telemetry
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/log/global"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+// SetupOTelSDK bootstraps the OpenTelemetry pipeline (propagator + traces +
+// metrics, and an opt-in logger — see NewLoggerProvider). It is shared by every
+// service main package; the service name comes from OTEL_RESOURCE_ATTRIBUTES, so
+// the same setup works everywhere. If it returns no error, call the returned
+// shutdown for proper cleanup.
+func SetupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
+	var shutdownFuncs []func(context.Context) error
+	var err error
+
+	// shutdown calls the registered cleanup functions, joining their errors.
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFuncs {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFuncs = nil
+		return err
+	}
+
+	// handleErr runs shutdown and surfaces all errors.
+	handleErr := func(inErr error) {
+		err = errors.Join(inErr, shutdown(ctx))
+	}
+
+	otel.SetTextMapPropagator(newPropagator())
+
+	tracerProvider, err := newTracerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
+	otel.SetTracerProvider(tracerProvider)
+
+	meterProvider, err := newMeterProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
+	otel.SetMeterProvider(meterProvider)
+
+	// Logger provider is opt-in via OTEL_LOGS_ENABLED; nil means logs are off.
+	// Traces + metrics above are always on.
+	loggerProvider, err := NewLoggerProvider(ctx)
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	if loggerProvider != nil {
+		shutdownFuncs = append(shutdownFuncs, loggerProvider.Shutdown)
+		global.SetLoggerProvider(loggerProvider)
+	}
+
+	return shutdown, err
+}
+
+func newPropagator() propagation.TextMapPropagator {
+	return propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+}
+
+func newTracerProvider() (*trace.TracerProvider, error) {
+	traceExporter, err := otlptracegrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+	return trace.NewTracerProvider(
+		trace.WithBatcher(traceExporter, trace.WithBatchTimeout(time.Second)),
+	), nil
+}
+
+func newMeterProvider() (*metric.MeterProvider, error) {
+	exporter, err := otlpmetricgrpc.New(context.Background())
+	if err != nil {
+		return nil, err
+	}
+	return metric.NewMeterProvider(metric.WithReader(metric.NewPeriodicReader(exporter))), nil
+}