前言#
上一篇介绍了客户端流式RPC，客户端不断的向服务端发送数据流，在发送结束或流关闭后，由服务端返回一个响应。本篇将介绍双向流式RPC。
双向流式RPC：客户端和服务端双方使用读写流去发送一个消息序列，两个流独立操作，双方可以同时发送和同时接收。
情景模拟：双方对话（可以一问一答、一问多答、多问一答，形式灵活）。
新建proto文件#
新建both_stream.proto文件
1.定义发送信息
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// 定义流式请求信息 message StreamRequest{ //流请求参数 string question = 1; }
2.定义接收信息
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// 定义流式响应信息 message StreamResponse{ //流响应数据 string answer = 1; }
3.定义服务方法Conversations
双向流式rpc，只要在请求的参数前和响应参数前都添加stream即可
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service Stream{ // 双向流式rpc，同时在请求参数前和响应参数前加上stream rpc Conversations(stream StreamRequest) returns(stream StreamResponse){}; }
4.编译proto文件
进入both_stream.proto所在目录，运行指令:
protoc --go_out=plugins=grpc:./ ./both_stream.proto
创建Server端#
1.定义我们的服务，并实现RouteList方法
这里简单实现对话中一问一答的形式
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`type StreamService struct{}
func (s *StreamService) Conversations(srv pb.Stream_ConversationsServer) error {
n := 1
for {
req, err := srv.Recv()
if err == io.EOF {
return nil
}
if err != nil {
return err
}
err = srv.Send(&pb.StreamResponse{
Answer: “from stream server answer: the “ + strconv.Itoa(n) + “ question is “ + req.Question,
})
if err != nil {
return err
}
n++
log.Printf(“from stream client question: %s”, req.Question)
}
}`
2.启动gRPC服务器
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`const (
Address string = ":8000"
Network string = "tcp"
)
func main() {
listener, err := net.Listen(Network, Address)
if err != nil {
log.Fatalf("net.Listen err: %v", err)
}
log.Println(Address + " net.Listing...")
grpcServer := grpc.NewServer()
pb.RegisterStreamServer(grpcServer, &StreamService{})
err = grpcServer.Serve(listener)
if err != nil {
log.Fatalf("grpcServer.Serve err: %v", err)
}
}`
运行服务端
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go run server.go :8000 net.Listing...
创建Client端#
1.创建调用服务端Conversations方法
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`func conversations() {
stream, err := streamClient.Conversations(context.Background())
if err != nil {
log.Fatalf("get conversations stream err: %v", err)
}
for n := 0; n < 5; n++ {
err := stream.Send(&pb.StreamRequest{Question: "stream client rpc " + strconv.Itoa(n)})
if err != nil {
log.Fatalf("stream request err: %v", err)
}
res, err := stream.Recv()
if err == io.EOF {
break
}
if err != nil {
log.Fatalf("Conversations get stream err: %v", err)
}
log.Println(res.Answer)
}
err = stream.CloseSend()
if err != nil {
log.Fatalf("Conversations close stream err: %v", err)
}
}`
2.启动gRPC客户端
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`const Address string = “:8000”
var streamClient pb.StreamClient
func main() {
conn, err := grpc.Dial(Address, grpc.WithInsecure())
if err != nil {
log.Fatalf("net.Connect err: %v", err)
}
defer conn.Close()
streamClient = pb.NewStreamClient(conn)
conversations()
}`
运行客户端，获取到服务端的应答
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go run client.go from stream server answer: the 1 question is stream client rpc 0 from stream server answer: the 2 question is stream client rpc 1 from stream server answer: the 3 question is stream client rpc 2 from stream server answer: the 4 question is stream client rpc 3 from stream server answer: the 5 question is stream client rpc 4
服务端获取到来自客户端的提问
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from stream client question: stream client rpc 0 from stream client question: stream client rpc 1 from stream client question: stream client rpc 2 from stream client question: stream client rpc 3 from stream client question: stream client rpc 4
总结#
本篇介绍了双向流式RPC的简单使用。
教程源码地址：https://github.com/Bingjian-Zhu/go-grpc-example
参考：gRPC官方文档中文版
