feat: initial version

otel.go

@@ -0,0 +1,100 @@
+package otelsetup
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutlog"
+	"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/trace"
+)
+
+// SetupOTelSDK bootstraps the OpenTelemetry pipeline.
+func SetupOTelSDK(ctx context.Context, enabled bool, serviceName string, buildVersion string) (func(context.Context) error, error) {
+	if os.Getenv("OTEL_RESOURCE_ATTRIBUTES") == "" {
+		if err := os.Setenv("OTEL_RESOURCE_ATTRIBUTES", fmt.Sprintf("service.name=%s,service.version=%s", serviceName, buildVersion)); err != nil {
+			return func(context.Context) error {
+				return nil
+			}, err
+		}
+	}
+	var shutdownFuncs []func(context.Context) error
+	if !enabled {
+		return func(context.Context) error {
+			return nil
+		}, nil
+	}
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFuncs {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFuncs = nil
+		return err
+	}
+
+	// handleErr calls shutdown for cleanup and makes sure that all errors are returned.
+	handleErr := func(inErr error) (func(context.Context) error, error) {
+		return nil, errors.Join(inErr, shutdown(ctx))
+	}
+
+	// Set up the propagator.
+	prop := propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+	otel.SetTextMapPropagator(prop)
+
+	traceExporter, err := otlptracehttp.New(ctx)
+	if err != nil {
+		return handleErr(err)
+	}
+	shutdownFuncs = append(shutdownFuncs, traceExporter.Shutdown)
+
+	tracerProvider := trace.NewTracerProvider(
+		trace.WithBatcher(traceExporter,
+			trace.WithBatchTimeout(5*time.Second)),
+	)
+	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
+	otel.SetTracerProvider(tracerProvider)
+
+	logExporter, err := stdoutlog.New()
+	if err != nil {
+		return handleErr(err)
+	}
+	processor := log.NewSimpleProcessor(logExporter)
+	logProvider := log.NewLoggerProvider(log.WithProcessor(processor))
+
+	global.SetLoggerProvider(logProvider)
+	shutdownFuncs = append(shutdownFuncs, logProvider.Shutdown)
+
+	exp, err := otlpmetrichttp.New(ctx)
+	if err != nil {
+		return handleErr(err)
+	}
+	meterProvider := metric.NewMeterProvider(metric.WithReader(metric.NewPeriodicReader(exp)))
+	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
+
+	otel.SetMeterProvider(meterProvider)
+	return shutdown, err
+}
+
+func Handler(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ctx := otel.GetTextMapPropagator().Extract(r.Context(), propagation.HeaderCarrier(r.Header))
+		spanCtx, s := StartSpan(ctx, "http")
+		defer s.Finish()
+
+		h.ServeHTTP(w, r.WithContext(spanCtx))
+	})
+}