snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

examples/features/flow_control/server/main.go

@@ -0,0 +1,111 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Binary server demonstrates how gRPC flow control block sending when the
+// receiver is not ready.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"time"
+
+	"google.golang.org/grpc"
+
+	pb "google.golang.org/grpc/examples/features/proto/echo"
+	"google.golang.org/grpc/internal/grpcsync"
+)
+
+var port = flag.Int("port", 50052, "port number")
+
+var payload = string(make([]byte, 8*1024)) // 8KB
+
+// server is used to implement EchoServer.
+type server struct {
+	pb.UnimplementedEchoServer
+}
+
+func (s *server) BidirectionalStreamingEcho(stream pb.Echo_BidirectionalStreamingEchoServer) error {
+	log.Printf("New stream began.")
+	// First, we wait 2 seconds before reading from the stream, to give the
+	// client an opportunity to block while sending its requests.
+	time.Sleep(2 * time.Second)
+
+	// Next, read all the data sent by the client to allow it to unblock.
+	for i := 0; true; i++ {
+		if _, err := stream.Recv(); err != nil {
+			log.Printf("Read %v messages.", i)
+			if err == io.EOF {
+				break
+			}
+			log.Printf("Error receiving data: %v", err)
+			return err
+		}
+	}
+
+	// Finally, send data until we block, then end the stream after we unblock.
+	stopSending := grpcsync.NewEvent()
+	sentOne := make(chan struct{})
+	go func() {
+		for !stopSending.HasFired() {
+			after := time.NewTimer(time.Second)
+			select {
+			case <-sentOne:
+				after.Stop()
+			case <-after.C:
+				log.Printf("Sending is blocked.")
+				stopSending.Fire()
+				<-sentOne
+			}
+		}
+	}()
+
+	i := 0
+	for !stopSending.HasFired() {
+		i++
+		if err := stream.Send(&pb.EchoResponse{Message: payload}); err != nil {
+			log.Printf("Error sending data: %v", err)
+			return err
+		}
+		sentOne <- struct{}{}
+	}
+	log.Printf("Sent %v messages.", i)
+
+	log.Printf("Stream ended successfully.")
+	return nil
+}
+
+func main() {
+	flag.Parse()
+
+	address := fmt.Sprintf(":%v", *port)
+	lis, err := net.Listen("tcp", address)
+	if err != nil {
+		log.Fatalf("failed to listen: %v", err)
+	}
+
+	grpcServer := grpc.NewServer()
+	pb.RegisterEchoServer(grpcServer, &server{})
+
+	if err := grpcServer.Serve(lis); err != nil {
+		log.Fatalf("failed to serve: %v", err)
+	}
+}