Micro: Add TraceProvider injector. (#4040)

* Micro: Add TraceProvider injector.

This allows to inject a TraceProvider into the service constructor,
instead of letting the service constructor create one.

* Add changelog.

changelog/unreleased/external-traceprovider-micro.md

@@ -0,0 +1,5 @@
+Enhancement: Allow to use external trace provider in micro service
+
+Allow injecting of external trace provider in the micro service instead of forcing the initialisation of an internal one.
+
+https://github.com/cs3org/reva/pull/4040

pkg/micro/ocdav/option.go

@@ -28,6 +28,7 @@ import (
 	"github.com/cs3org/reva/v2/pkg/storage/favorite"
 	"github.com/rs/zerolog"
 	"go-micro.dev/v4/broker"
+	"go.opentelemetry.io/otel/trace"
 )
 
 // Option defines a single option function.
@@ -54,6 +55,8 @@ type Options struct {
 	TracingCollector string
 	TracingEndpoint  string
 
+	TraceProvider trace.TracerProvider
+
 	MetricsEnabled   bool
 	MetricsNamespace string
 	MetricsSubsystem string
@@ -234,6 +237,13 @@ func WithTracingExporter(exporter string) Option {
 	}
 }
 
+// WithTraceProvider option
+func WithTraceProvider(provider trace.TracerProvider) Option {
+	return func(o *Options) {
+		o.TraceProvider = provider
+	}
+}
+
 // Version provides a function to set the Version config option.
 func Version(val string) Option {
 	return func(o *Options) {

pkg/micro/ocdav/service.go

@@ -51,7 +51,6 @@ const (
 
 // Service initializes the ocdav service and underlying http server.
 func Service(opts ...Option) (micro.Service, error) {
-
 	sopts := newOptions(opts...)
 
 	// set defaults
@@ -86,19 +85,23 @@ func Service(opts ...Option) (micro.Service, error) {
 	// chi.RegisterMethod(ocdav.MethodMkcol)
 	// chi.RegisterMethod(ocdav.MethodReport)
 	r := chi.NewRouter()
-	topts := []rtrace.Option{
-		rtrace.WithExporter(sopts.TracingExporter),
-		rtrace.WithEndpoint(sopts.TracingEndpoint),
-		rtrace.WithCollector(sopts.TracingCollector),
-		rtrace.WithServiceName(sopts.Name),
-	}
-	if sopts.TracingEnabled {
-		topts = append(topts, rtrace.WithEnabled())
-	}
-	if sopts.TracingInsecure {
-		topts = append(topts, rtrace.WithInsecure())
+	tp := sopts.TraceProvider
+
+	if tp == nil {
+		topts := []rtrace.Option{
+			rtrace.WithExporter(sopts.TracingExporter),
+			rtrace.WithEndpoint(sopts.TracingEndpoint),
+			rtrace.WithCollector(sopts.TracingCollector),
+			rtrace.WithServiceName(sopts.Name),
+		}
+		if sopts.TracingEnabled {
+			topts = append(topts, rtrace.WithEnabled())
+		}
+		if sopts.TracingInsecure {
+			topts = append(topts, rtrace.WithInsecure())
+		}
+		tp = rtrace.NewTracerProvider(topts...)
 	}
-	tp := rtrace.NewTracerProvider(topts...)
 	if err := useMiddlewares(r, &sopts, revaService, tp); err != nil {
 		return nil, err
 	}
@@ -132,7 +135,6 @@ func Service(opts ...Option) (micro.Service, error) {
 }
 
 func setDefaults(sopts *Options) error {
-
 	// set defaults
 	if sopts.Name == "" {
 		sopts.Name = ServerName