Ok, 先来安装 gRPC 的开发环境，并且实践一下 Hello World 程序吧！

1. 开发环境

ENV: go version go1.11 windows/amd64
IDE: goland

使用 gRPC 需要安装以下开发环境

  • Install gRPC (RPC框架)
  • Install Protocol Buffers v3 (Google推出的一种数据描述语言)
  • Install the protoc plugin for Go (编译器插件)

有关 gRPC、Protocol Buffers 的详细介绍会在后面章节补充, 这里先了解一下即可，主要目的先快速熟悉一下 gRPC.

2. 安装 gRPC

具体过程参考官方的 Quick Start 即可，下面给出一些遇到的一些问题和解决方法

如果通过官方推荐的方式，即(go get -u google.golang.org/grpc)需要满足以下两个条件：

  • 科学上网
  • Proxifier: 用于配置全局代理，具体使用可参考 Here, 或自行 Google

否则，是无法完成下载的, 错误可能为：

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package google.golang.org/grpc: unrecognized import path "google.golang.org/grpc"(https fetch: Get https://google.golang.org/grpc?go-get=1: dial tcp 216.239.37.1:443: i/o timeout)

解决方法参考：Golang安装gRPC报错问题的解决方法

3. Hello World Demo

Reference from Here and Here

3.1. Setup a repo

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$ mkdir -p go-grpc/helloworld
$ cd go-grpc
$ go mod init go-grpc

Note: goland 使用 Go Modules 时需要启用：Go Module(vgo) (Ctrl+Alt+S -> Go -> Go Module(vgo) -> Enable ✔)

3.2. Make a file helloworld/helloworld.proto for protocol buffers

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// gRPC: helloworld demo

syntax = "proto3";

package helloworld;

// The greeting service definition.
service Greeter {
    // Send a greeting
    rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The resquest message containing the user's name.
message HelloRequest {
    string name = 1;
}

// The response message containing the greetings.
message HelloReply {
    string message = 1;
}

3.3. Generate a go file from protocol buffers

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$ protoc --go_out=plugins=grpc:. helloworld/helloworld.proto
$ ls helloworld
helloworld.pb.go  helloworld.proto

执行完成后会生成一个：helloworld.pb.go 文件

3.4. Make a gRPC server file server/main.go

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/*
 * 说明：gRPC: helloworld demo
 * 作者：zhe
 * 时间：2018-09-05 1:40 PM
 * 更新：
 */

package main

import (
	"context"
	"log"
	"net"

	"google.golang.org/grpc"
	"google.golang.org/grpc/reflection"

	pb "go-grpc/helloworld"
)

const port = ":50051"

type server struct{}

func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	return &pb.HelloReply{Message: "Hello " + in.Name}, nil
}

func main() {
	lis, err := net.Listen("tcp", port)
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}

	s := grpc.NewServer()
	pb.RegisterGreeterServer(s, &server{})
	reflection.Register(s)
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to server: %v", err)
	}
}

3.5. Make a gRPC client file client/main.go

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/*
 * 说明：gRPC: helloworld demo
 * 作者：zhe
 * 时间：2018-09-05 1:46 PM
 * 更新：
 */

package main

import (
	"context"
	"log"
	"os"
	"time"

	"google.golang.org/grpc"

	pb "go-grpc/helloworld"
)

const (
	address     = "localhost:50051"
	defaultName = "world"
)

func main() {
	conn, err := grpc.Dial(address, grpc.WithInsecure())
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()
	c := pb.NewGreeterClient(conn)

	name := defaultName
	if len(os.Args) > 1 {
		name = os.Args[1]
	}
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	r, err := c.SayHello(ctx, &pb.HelloRequest{Name: name})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	log.Printf("Greeting: %v", r.Message)
}

3.6. Try it out!

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$ go run server/main.go

Open a new termial

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$ go run client/main.go
2018/09/05 16:16:15 Greeting: Hello world

Maybe, you can try more. Continue…

4. Update a gRPC service

4.1. Update .proto

给 helloworld/helloworld.proto 再添加一个方法：SayHelloAgain, request and response 类型同 SayHello 函数

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// gRPC: helloworld demo

syntax = "proto3";

package helloworld;

// The greeting service definition.
service Greeter {
    // Send a greeting
    rpc SayHello (HelloRequest) returns (HelloReply) {}
    // Sends another greeting
    rpc SayHelloAgain (HelloRequest) returns (HelloReply) {}
}

// The resquest message containing the user's name.
message HelloRequest {
    string name = 1;
}

// The response message containing the greetings.
message HelloReply {
    string message = 1;
}

4.2. Generate gRPC code

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$ protoc -I helloworld/ helloworld/helloworld.proto --go_out=plugins=grpc:helloworld

4.3. Update and run the application

4.3.1. Update Server

给 type server struct{} 添加方法：SayHelloAgain, 即：

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func (s *server) SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	return &pb.HelloReply{Message: "Hello again " + in.Name}, nil
}

4.3.2. Update Client

在客户端程序中调用 SayHelloAgain：

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r, err = c.SayHelloAgain(ctx, &pb.HelloRequest{Name: name})
if err != nil {
        log.Fatalf("could not greet: %v", err)
}
log.Printf("Greeting: %s", r.Message)

4.4. Run

run the server:

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[zhe@zhe go-grpc]$ go run server/main.go

run the client:

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[zhe@zhe go-grpc]$ go run client/main.go
2018/09/05 16:35:03 Greeting: Hello world
2018/09/05 16:35:03 Greeting: Hello again world

Now, the end.

5. See Also

Thanks to the authors 🙂