wonderwall/pkg/otel/otel.go

package otel

import (
	"context"
	"errors"
	"time"

	"github.com/nais/wonderwall/pkg/config"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/resource"
	"go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/semconv/v1.21.0"
)

func Setup(ctx context.Context, cfg *config.Config) (shutdown func(context.Context) error, err error) {
	var shutdownFuncs []func(context.Context) error

	shutdown = func(ctx context.Context) error {
		var err error
		for _, fn := range shutdownFuncs {
			err = errors.Join(err, fn(ctx))
		}
		shutdownFuncs = nil
		return err
	}

	handleErr := func(inErr error) {
		err = errors.Join(inErr, shutdown(ctx))
	}

	res, err := newResource(cfg.OpenTelemetry.ServiceName, cfg.Version)
	if err != nil {
		handleErr(err)
		return
	}

	otel.SetTextMapPropagator(newPropagator())

	tracerProvider, err := newTraceProvider(ctx, res)
	if err != nil {
		handleErr(err)
		return
	}
	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
	otel.SetTracerProvider(tracerProvider)

	return
}

func newResource(serviceName, serviceVersion string) (*resource.Resource, error) {
	return resource.Merge(resource.Default(),
		resource.NewWithAttributes(semconv.SchemaURL,
			semconv.ServiceName(serviceName),
			semconv.ServiceVersion(serviceVersion),
		))
}

func newPropagator() propagation.TextMapPropagator {
	return propagation.NewCompositeTextMapPropagator(
		propagation.TraceContext{},
		propagation.Baggage{},
	)
}

func newTraceProvider(ctx context.Context, res *resource.Resource) (*trace.TracerProvider, error) {
	traceExporter, err := otlptracegrpc.New(ctx)
	if err != nil {
		return nil, err
	}

	traceProvider := trace.NewTracerProvider(
		trace.WithBatcher(traceExporter,
			trace.WithBatchTimeout(5*time.Second)),
		trace.WithResource(res),
	)
	return traceProvider, nil
}