store/tikv: tiny optimize when opentracing is not enabled (pingcap#6494)

store/tikv/client.go

@@ -99,15 +99,21 @@ func (a *connArray) Init(addr string, security config.Security) error {
 		opt = grpc.WithTransportCredentials(credentials.NewTLS(tlsConfig))
 	}
 
-	for i := range a.v {
-		unaryInterceptor := grpc_middleware.ChainUnaryClient(
-			grpc_prometheus.UnaryClientInterceptor,
+	unaryInterceptor := grpc_prometheus.UnaryClientInterceptor
+	streamInterceptor := grpc_prometheus.StreamClientInterceptor
+	cfg := config.GetGlobalConfig()
+	if cfg.OpenTracing.Enable {
+		unaryInterceptor = grpc_middleware.ChainUnaryClient(
+			unaryInterceptor,
 			grpc_opentracing.UnaryClientInterceptor(),
 		)
-		streamInterceptor := grpc_middleware.ChainStreamClient(
-			grpc_prometheus.StreamClientInterceptor,
+		streamInterceptor = grpc_middleware.ChainStreamClient(
+			streamInterceptor,
 			grpc_opentracing.StreamClientInterceptor(),
 		)
+	}
+
+	for i := range a.v {
 
 		ctx, cancel := context.WithTimeout(context.Background(), dialTimeout)
 		conn, err := grpc.DialContext(

store/tikv/coprocessor.go

@@ -394,8 +394,10 @@ const minLogCopTaskTime = 300 * time.Millisecond
 // run is a worker function that get a copTask from channel, handle it and
 // send the result back.
 func (worker *copIteratorWorker) run(ctx context.Context) {
-	span, ctx1 := opentracing.StartSpanFromContext(ctx, "copIteratorWorker.run")
-	defer span.Finish()
+	if span := opentracing.SpanFromContext(ctx); span != nil {
+		span, ctx = opentracing.StartSpanFromContext(ctx, "copIteratorWorker.run")
+		defer span.Finish()
+	}
 
 	defer worker.wg.Done()
 	for task := range worker.taskCh {
@@ -404,7 +406,7 @@ func (worker *copIteratorWorker) run(ctx context.Context) {
 			respCh = task.respChan
 		}
 
-		bo := NewBackoffer(ctx1, copNextMaxBackoff).WithVars(worker.vars)
+		bo := NewBackoffer(ctx, copNextMaxBackoff).WithVars(worker.vars)
 		worker.handleTask(bo, task, respCh)
 		if bo.totalSleep > 0 {
 			metrics.TiKVBackoffHistogram.Observe(float64(bo.totalSleep) / 1000)