golang-gRPC (Mac)

Hello World Protocol Buffer

Preparing

• Protocol buffer(protobuf) Version 3

> brew update && brew install protobuf

Create a go project(ex: lets-learn-golang-grpc)

> mkdir lets-learn-golang-grpc
> cd lets-learn-golang-grpc
llgg > go mod init lets-learn-golang-grpc
llgg > go get -u google.golang.org/grpc
llgg > go get -u google.golang.org/protobuf/proto
llgg > go get -u google.golang.org/grpc/cmd/protoc-gen-go-grpc

The go modules will be used whole the project.

Create a `chapter-00` for `helloworld` such as,

├── chapter-00
│   └── helloworld
│       ├── README.md
│       ├── client
│       │   └── main.go
│       ├── pb
│       │   ├── helloworld.proto
│       └── server
│           └── main.go
├── go.mod
└── go.sum

Create `pb/helloworld.proto`

syntax = "proto3";

option go_package = "lets-learn-golang-grpc/chapter-00/helloworld/pb";

package pb;

// The service definition
service HelloWorld {
    // Sends the SayHello message
    rpc SayHello (HelloRequest) returns (HelloResponse) {}
}

// The request message containing a name(Client-side)
message HelloRequest {
    string name = 1;
}

// The response message containing a message(Server-side)
message HelloResponse {
    string message = 1;
}

The name will receive from the client (user) and send a message to the client .

Generate go codes with `pb/helloworld.proto`

chapter-00/helloworld > protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=. --go-grpc_opt=paths=source_relative pb/helloworld.proto

This will create two go codes, helloworld.pb.go and helloworld_grpc.pb.go.

├── pb
    ├── helloworld.pb.go
    ├── helloworld.proto
    └── helloworld_grpc.pb.go

Create a server `server/main.go`

package main

import (
	"context"
	"lets-learn-golang-grpc/chapter-00/helloworld/pb"
	"log"
	"net"

	"google.golang.org/grpc"
)

const (
	port = ":50051"
)

type server struct {
	pb.UnimplementedHelloWorldServer
}

// SayHello implements a server
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloResponse, error) {
	log.Printf("Received: %v", in.GetName())
	return &pb.HelloResponse{Message: "Hello " + in.GetName()}, nil
}

func main() {
	lis, err := net.Listen("tcp", port)
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := grpc.NewServer()
	pb.RegisterHelloWorldServer(s, &server{})
	log.Printf("server listening at %v", lis.Addr())
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}

This server will return a message “Hello ” and a name that user send.

Create a client `client/main.go`

package main

import (
	"context"
	"lets-learn-golang-grpc/chapter-00/helloworld/pb"
	"log"
	"os"
	"time"

	"google.golang.org/grpc"
)

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

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

	c := pb.NewHelloWorldClient(conn)

	// get a name otherwise defaultName
	name := defaultName
	if (len(os.Args)) > 1 {
		name = os.Args[1]
	}

	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
	defer cancel()
	r, err := c.SayHello(ctx, &pb.HelloRequest{Name: name})
	if err != nil {
		log.Fatalf("could not say: %v", err)
	}
	log.Printf("Say: %s", r.GetMessage())
}

This server will send a name to server and receive a message from the server. The default name is World .

Directory tree

.
├── chapter-00
│   └── helloworld
│       ├── README.md
│       ├── client
│       │   └── main.go
│       ├── pb
│       │   ├── helloworld.pb.go
│       │   ├── helloworld.proto
│       │   └── helloworld_grpc.pb.go
│       └── server
│           └── main.go
├── go.mod
└── go.sum

Run the server in the root of project or the server directory

> go run ./chapter-00/server/main.go

Run the client in the root of project or the client directory

> go run ./chapter-00/client/main.go

The result is

> Say: Hello World

When you put a name such as

> go run ./chapter-00/server/main.go Alice

you will have

> Say: Hello Alice

This is a very simple golang-gRPC example.

https://github.com/abc101/lets-learn-golang-grpc