【go网络编程】-RPC编程

RPC介绍

Remote Procedure Call，远程过程调用

解决问题

而一旦踏入公司尤其是大型互联网公司就会发现，公司的系统都由成千上万大大小小的服务组成，各服务部署在不同的机器上，由不同的团队负责。这时就会遇到两个问题：
1）要搭建一个新服务，免不了需要依赖他人的服务，而现在他人的服务都在远端，怎么调用？
2）其它团队要使用我们的服务，我们的服务该怎么发布以便他人调用？

过程

1. 服务消费方（client）调用以本地调用方式调用服务；
2. client stub接收到调用后负责将方法、参数等组装成能够进行网络传输的消息体；
3. client stub找到服务地址，并将消息发送到服务端；
4. server stub收到消息后进行解码；
5. server stub根据解码结果调用本地的服务；
6. 本地服务执行并将结果返回给server stub；
7. server stub将返回结果打包成消息并发送至消费方；
8. client stub接收到消息，并进行解码；
9. 服务消费方得到最终结果。

RPC的目标就是要2~8这些步骤都封装起来，让用户对这些细节透明。

实现方式

RPC可以通过HTTP来实现（grpc基于http2.0）,也可以通过Socket自己实现一套协议来实现.

grpc框架

4种通信方式

• 简单rpc：一个请求对象对应一个返回对象

rpc simpleHello(Person) returns (Result) {}

• 服务端流式rpc ：一个请求对象，服务端可以传回多个结果对象

rpc serverStreamHello(Person) returns (stream Result) {}

• 客户端流式rpc：客户端传入多个请求对象，服务端返回一个响应结果

rpc clientStreamHello(stream Person) returns (Result) {}

• 双向流式rpc：可以传入多个对象，返回多个响应对象

rpc biStreamHello(stream Person) returns (stream Result) {}

案例

simple.proto

syntax = "proto3";
package testRPC;

service testRPC {

    rpc simple (emit) returns (on) {
    }
    rpc serverStream (emit) returns (stream on){}
    rpc clientStream (stream emit) returns (on){}
    rpc bothStream (stream emit) returns (stream on){}
}

message emit{
    string type = 1;
    string name = 2;
}

message on{
    string type = 1;
    int32 age = 2;
}

service

package main

import (
    "net"
    "google.golang.org/grpc"
    pb "google.golang.org/grpc/examples/test/proto"
    "google.golang.org/grpc/reflection"
    "fmt"
    "golang.org/x/net/context"
    "io"
)

const (
    port = ":50051"
)

type server struct {
}

func (s *server) Simple(ctx context.Context, in *pb.Emit) (*pb.On, error) {
    return &pb.On{Type: "Hello " + in.Type, Age: 10}, nil
}
func (s *server) ServerStream(in *pb.Emit, stream pb.TestRPC_ServerStreamServer) (error) {
    for i := 1; i < 10; i++ {
        if err := stream.Send(&pb.On{Type: "Hello " + in.Type, Age: int32(i)}); err != nil {
            return err
        }
    }
    return nil
}
func (s *server) ClientStream(stream pb.TestRPC_ClientStreamServer) (error) {
    var pointCount int32
    for {
        _, err := stream.Recv()
        if err == io.EOF {
            return stream.SendAndClose(&pb.On{
                Type: "end",
                Age:  pointCount,
            })
        }
        pointCount++
    }
}

func (s *server) BothStream(stream pb.TestRPC_BothStreamServer) (error) {
    for {
        emit, err := stream.Recv()
        if err == io.EOF {
            return nil
        }
        fmt.Println(string(emit.Type))
        for i := 1; i < 3; i++ {
            if err := stream.Send(&pb.On{Type: emit.Type, Age: int32(i)}); err != nil {
                return err
            }
        }

    }
    return nil
}

func main() {
    lis, _ := net.Listen("tcp", port)
    s := grpc.NewServer()
    pb.RegisterTestRPCServer(s, &server{})
    reflection.Register(s)
    if err := s.Serve(lis); err != nil {
        fmt.Println("error")
    }
}

client

package main

import (
    "google.golang.org/grpc"
    pb "google.golang.org/grpc/examples/test/proto"
    "golang.org/x/net/context"
    "time"
    "log"
    "io"
)

const (
    address = "localhost:50051"
)

func main() {
    conn, _ := grpc.Dial(address, grpc.WithInsecure())
    defer conn.Close()

    rpcClient := pb.NewTestRPCClient(conn)

    testSimple(rpcClient)

    testServerStream(rpcClient)

    testClientStream(rpcClient)

    testBothStream(rpcClient)

}

func testSimple(client pb.TestRPCClient) {
    ctx, cancel := context.WithTimeout(context.Background(), time.Second)
    defer cancel()
    // simple
    r, _ := client.Simple(ctx, &pb.Emit{Type: "11"})
    log.Printf("Greeting: %s", r)
}

func testServerStream(client pb.TestRPCClient) {
    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()
    stream, err := client.ServerStream(ctx, &pb.Emit{Type: "Hello "})
    if err != nil {
        log.Fatalf("%v.ListFeatures(_) = _, %v", client, err)
    }
    for {
        feature, err := stream.Recv()
        if err == io.EOF {
            break
        }
        if err != nil {
            log.Fatalf("%v.ListFeatures(_) = _, %v", client, err)
        }
        log.Println(feature)
    }
}

func testClientStream(client pb.TestRPCClient) {
    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()
    stream, err := client.ClientStream(ctx)
    if err != nil {
        log.Fatalf("%v.RecordRoute(_) = _, %v", client, err)
    }
    var points []pb.Emit
    for i := 0; i < 10; i++ {
        points = append(points, pb.Emit{Type: "t", Name: string(i)})
    }
    for _, point := range points {
        if err := stream.Send(&point); err != nil {
            log.Fatalf("%v.Send(%v) = %v", stream, point, err)
        }
    }
    reply, err := stream.CloseAndRecv()
    if err != nil {
        log.Fatalf("%v.CloseAndRecv() got error %v, want %v", stream, err, nil)
    }
    log.Printf("Route summary: %v", reply)
}

func testBothStream(client pb.TestRPCClient) {
    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()
    stream, err := client.BothStream(ctx)
    if err != nil {
        log.Fatalf("%v.RecordRoute(_) = _, %v", client, err)
    }
    var points []pb.Emit
    for i := 0; i < 10; i++ {
        points = append(points, pb.Emit{Type: "xiaoming"+string(i), Name: "xiaohong"})
    }
    waitc := make(chan struct{})
    go func() {
        for {
            on, err := stream.Recv()
            if err == io.EOF {
                // read done.
                close(waitc)
                return
            }
            if err != nil {
                log.Fatalf("Failed to receive a note : %v", err)
            }
            log.Printf("Got message %s = %d)", on.Type, on.Age)
        }
    }()
    for _, point := range points {
        if err := stream.Send(&point); err != nil {
            log.Fatalf("Failed to send a note: %v", err)
        }
    }
    stream.CloseSend()
    <-waitc
}