tracer autodetection for client interceptors

Ability to automatically get tracer from request context if no tracer
were passed to constructor.

Author: funny-falcon

tracing/opentracing/client_interceptors.go

@@ -25,6 +25,9 @@ func UnaryClientInterceptor(opts ...Option) grpc.UnaryClientInterceptor {
 			return invoker(parentCtx, method, req, reply, cc, opts...)
 		}
 		newCtx, clientSpan := newClientSpanFromContext(parentCtx, o.tracer, method)
+		if clientSpan == nil {
+			return invoker(parentCtx, method, req, reply, cc, opts...)
+		}
 		err := invoker(newCtx, method, req, reply, cc, opts...)
 		finishClientSpan(clientSpan, err)
 		return err
@@ -39,6 +42,9 @@ func StreamClientInterceptor(opts ...Option) grpc.StreamClientInterceptor {
 			return streamer(parentCtx, desc, cc, method, opts...)
 		}
 		newCtx, clientSpan := newClientSpanFromContext(parentCtx, o.tracer, method)
+		if clientSpan == nil {
+			return streamer(parentCtx, desc, cc, method, opts...)
+		}
 		clientStream, err := streamer(newCtx, desc, cc, method, opts...)
 		if err != nil {
 			finishClientSpan(clientSpan, err)
@@ -112,6 +118,15 @@ func newClientSpanFromContext(ctx context.Context, tracer opentracing.Tracer, fu
 	var parentSpanCtx opentracing.SpanContext
 	if parent := opentracing.SpanFromContext(ctx); parent != nil {
 		parentSpanCtx = parent.Context()
+		if tracer == nil {
+			tracer = parent.Tracer()
+		}
+	}
+	if tracer == nil {
+		tracer = opentracing.GlobalTracer()
+		if _, ok := tracer.(opentracing.NoopTracer); ok {
+			return ctx, nil
+		}
 	}
 	opts := []opentracing.StartSpanOption{
 		opentracing.ChildOf(parentSpanCtx),

tracing/opentracing/interceptors_test.go

@@ -82,7 +82,19 @@ func TestTaggingSuite(t *testing.T) {
 	}
 	s := &OpentracingSuite{
 		mockTracer:           mockTracer,
-		InterceptorTestSuite: makeInterceptorTestSuite(t, opts),
+		InterceptorTestSuite: makeInterceptorTestSuite(t, opts, opts),
+	}
+	suite.Run(t, s)
+}
+
+func TestTaggingSuite2(t *testing.T) {
+	mockTracer := mocktracer.New()
+	opts := []grpc_opentracing.Option{
+		grpc_opentracing.WithTracer(mockTracer),
+	}
+	s := &OpentracingSuite{
+		mockTracer:           mockTracer,
+		InterceptorTestSuite: makeInterceptorTestSuite(t, nil, opts),
 	}
 	suite.Run(t, s)
 }
@@ -96,26 +108,26 @@ func TestTaggingSuiteJaeger(t *testing.T) {
 	}
 	s := &OpentracingSuite{
 		mockTracer:           mockTracer,
-		InterceptorTestSuite: makeInterceptorTestSuite(t, opts),
+		InterceptorTestSuite: makeInterceptorTestSuite(t, opts, opts),
 	}
 	suite.Run(t, s)
 }
 
-func makeInterceptorTestSuite(t *testing.T, opts []grpc_opentracing.Option) *grpc_testing.InterceptorTestSuite {
+func makeInterceptorTestSuite(t *testing.T, clientOpts, serverOpts []grpc_opentracing.Option) *grpc_testing.InterceptorTestSuite {
 
 	return &grpc_testing.InterceptorTestSuite{
 		TestService: &tracingAssertService{TestServiceServer: &grpc_testing.TestPingService{T: t}, T: t},
 		ClientOpts: []grpc.DialOption{
-			grpc.WithUnaryInterceptor(grpc_opentracing.UnaryClientInterceptor(opts...)),
-			grpc.WithStreamInterceptor(grpc_opentracing.StreamClientInterceptor(opts...)),
+			grpc.WithUnaryInterceptor(grpc_opentracing.UnaryClientInterceptor(clientOpts...)),
+			grpc.WithStreamInterceptor(grpc_opentracing.StreamClientInterceptor(clientOpts...)),
 		},
 		ServerOpts: []grpc.ServerOption{
 			grpc_middleware.WithStreamServerChain(
 				grpc_ctxtags.StreamServerInterceptor(grpc_ctxtags.WithFieldExtractor(grpc_ctxtags.CodeGenRequestFieldExtractor)),
-				grpc_opentracing.StreamServerInterceptor(opts...)),
+				grpc_opentracing.StreamServerInterceptor(serverOpts...)),
 			grpc_middleware.WithUnaryServerChain(
 				grpc_ctxtags.UnaryServerInterceptor(grpc_ctxtags.WithFieldExtractor(grpc_ctxtags.CodeGenRequestFieldExtractor)),
-				grpc_opentracing.UnaryServerInterceptor(opts...)),
+				grpc_opentracing.UnaryServerInterceptor(serverOpts...)),
 		},
 	}
 }

tracing/opentracing/options.go

@@ -32,9 +32,6 @@ func evaluateOptions(opts []Option) *options {
 	for _, o := range opts {
 		o(optCopy)
 	}
-	if optCopy.tracer == nil {
-		optCopy.tracer = opentracing.GlobalTracer()
-	}
 	return optCopy
 }
 
@@ -50,6 +47,10 @@ func WithFilterFunc(f FilterFunc) Option {
 // WithTracer sets a custom tracer to be used for this middleware, otherwise the opentracing.GlobalTracer is used.
 func WithTracer(tracer opentracing.Tracer) Option {
 	return func(o *options) {
-		o.tracer = tracer
+		if tracer == nil {
+			o.tracer = opentracing.GlobalTracer()
+		} else {
+			o.tracer = tracer
+		}
 	}
 }

tracing/opentracing/server_interceptors.go

@@ -56,6 +56,10 @@ func newServerSpanFromInbound(ctx context.Context, tracer opentracing.Tracer, fu
 		grpclog.Printf("grpc_opentracing: failed parsing trace information: %v", err)
 	}
 
+	if tracer == nil {
+		tracer = opentracing.GlobalTracer()
+	}
+
 	serverSpan := tracer.StartSpan(
 		fullMethodName,
 		// this is magical, it attaches the new span to the parent parentSpanContext, and creates an unparented one if empty.