fix: outputs.opentelemetry use headers config in grpc requests (#9587)

plugins/outputs/opentelemetry/opentelemetry.go

@@ -13,6 +13,7 @@ import (
 	"go.opentelemetry.io/collector/model/otlpgrpc"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/metadata"
 )
 
 type OpenTelemetry struct {
@@ -160,6 +161,10 @@ func (o *OpenTelemetry) Write(metrics []telegraf.Metric) error {
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(o.Timeout))
+
+	if len(o.Headers) > 0 {
+		ctx = metadata.NewOutgoingContext(ctx, metadata.New(o.Headers))
+	}
 	defer cancel()
 	_, err := o.metricsServiceClient.Export(ctx, md, o.callOptions...)
 	return err

plugins/outputs/opentelemetry/opentelemetry_test.go

@@ -18,6 +18,7 @@ import (
 	"go.opentelemetry.io/collector/model/otlpgrpc"
 	"go.opentelemetry.io/collector/model/pdata"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
 )
 
 func TestOpenTelemetry(t *testing.T) {
@@ -43,6 +44,7 @@ func TestOpenTelemetry(t *testing.T) {
 	plugin := &OpenTelemetry{
 		ServiceAddress:       m.Address(),
 		Timeout:              config.Duration(time.Second),
+		Headers:              map[string]string{"test": "header1"},
 		metricsConverter:     metricsConverter,
 		grpcClientConn:       m.GrpcClient(),
 		metricsServiceClient: otlpgrpc.NewMetricsClient(m.GrpcClient()),
@@ -131,5 +133,8 @@ func (m *mockOtelService) Address() string {
 
 func (m *mockOtelService) Export(ctx context.Context, request pdata.Metrics) (otlpgrpc.MetricsResponse, error) {
 	m.metrics = request.Clone()
+	ctxMetadata, ok := metadata.FromIncomingContext(ctx)
+	assert.Equal(m.t, []string{"header1"}, ctxMetadata.Get("test"))
+	assert.True(m.t, ok)
 	return otlpgrpc.MetricsResponse{}, nil
 }