Go语言版本的Protobuf-RPC基本算完成了. 现在简单说下使用方法.

安装测试环境

先下载代码(不支持go get):

hg clone https://bitbucket.org/chai2010/gopath

然后下载后的目录设置为GOPATH, 并添加$GOPATH/bin到PATH环境变量.

在$GOPATH/bin中已经包含了Windows下的2.4.1版本的protoc.exe. 如果是Linux等系统, 请自行下载并安装protoc程序.

安装protoc.exe的Go语言插件:

go install encoding/protobuf/protoc-gen-go

该插件是基于code.google.com/p/goprotobuf/protoc-gen-go实现, 主要增加了encoding/protobuf/protoc-gen-go/generator/service.go文件, 用于RPC的代码生成. 生成的RPC代码依赖net/rpc/protorpc, 这个包是Protobuf-RPC的底层实现, 可以单独使用.

现在可以运行一下测试程序:

C:\>go test net/rpc/protorpc/service.pb
ok      net/rpc/protorpc/service.pb     2.123s

测试通过, 继续.

---

编译 proto 文件

创建一个名为pbrpc的工作目录, 再创建pbrpc/arith.pb的子目录. 将net/rpc/protorpc/service.pb/service.proto文件复制到pbrpc/arith.pb的子目录.

包名字改为arith, 文件arith.proto的内容如下:

package arith;

option cc_generic_services = true;
option java_generic_services = true;
option py_generic_services = true;

message ArithRequest {
    optional int32 a = 1;
    optional int32 b = 2;
}

message ArithResponse {
    optional int32 c = 1;
}

service ArithService {
    rpc add (ArithRequest) returns (ArithResponse);
    rpc mul (ArithRequest) returns (ArithResponse);
    rpc div (ArithRequest) returns (ArithResponse);
    rpc error (ArithRequest) returns (ArithResponse);
}

主要是定义了一个ArithService接口. 要注意的是cc_generic_services/java_generic_services, py_generic_services几个选项. 我前提提到的protoc-gen-go在生成代码的时候, 这3个选项至少要有一个为true, 才会生成RPC的代码.

当然, 如果不生成RPC代码的话, 也是可以单独使用net/rpc/protorpc包的. 不过protoc-gen-go生成的代码会简便很多.

进入pbrpc/arith.pb的子目录, 编译arith.proto文件:

protoc --go_out=. arith.proto

生成 arith.pb.go 文件, 其中RPC的代码主要是下面这些:

type ArithService interface {
    Add(in *ArithRequest, out *ArithResponse) error
    Mul(in *ArithRequest, out *ArithResponse) error
    Div(in *ArithRequest, out *ArithResponse) error
    Error(in *ArithRequest, out *ArithResponse) error
}

// RegisterArithService publish the given ArithService implementation on the server.
func RegisterArithService(srv *rpc.Server, x ArithService) error {
    if err := srv.RegisterName("ArithService", x); err != nil {
        return err
    }
    return nil
}

// ServeArithService serves the given ArithService implementation on conn.
func ServeArithService(conn io.ReadWriteCloser, x ArithService) error {
    srv := rpc.NewServer()
    if err := srv.RegisterName("ArithService", x); err != nil {
        return err
    }
    srv.ServeCodec(protorpc.NewServerCodec(conn))
    return nil
}

// ListenAndServeArithService listen announces on the local network address laddr
// and serves the given ArithService implementation.
func ListenAndServeArithService(network, addr string, x ArithService) error {
    clients, err := net.Listen(network, addr)
    if err != nil {
        return err
    }
    srv := rpc.NewServer()
    if err := srv.RegisterName("ArithService", x); err != nil {
        return err
    }
    for {
        conn, err := clients.Accept()
        if err != nil {
            return err
        }
        go srv.ServeCodec(protorpc.NewServerCodec(conn))
    }
    panic("unreachable")
}

type rpcArithServiceStub struct {
    *rpc.Client
}

func (c *rpcArithServiceStub) Add(in *ArithRequest, out *ArithResponse) error {
    return c.Call("ArithService.Add", in, out)
}
func (c *rpcArithServiceStub) Mul(in *ArithRequest, out *ArithResponse) error {
    return c.Call("ArithService.Mul", in, out)
}
func (c *rpcArithServiceStub) Div(in *ArithRequest, out *ArithResponse) error {
    return c.Call("ArithService.Div", in, out)
}
func (c *rpcArithServiceStub) Error(in *ArithRequest, out *ArithResponse) error {
    return c.Call("ArithService.Error", in, out)
}

// DialArithService connects to an ArithService at the specified network address.
func DialArithService(network, addr string) (*rpc.Client, ArithService, error) {
    conn, err := net.Dial(network, addr)
    if err != nil {
        return nil, nil, err
    }
    c, srv := NewArithServiceClient(conn)
    return c, srv, nil
}

// NewArithServiceClient returns a ArithService rpc.Client and stub to handle
// requests to the set of ArithService at the other end of the connection.
func NewArithServiceClient(conn io.ReadWriteCloser) (*rpc.Client, ArithService) {
    c := rpc.NewClientWithCodec(protorpc.NewClientCodec(conn))
    return c, &rpcArithServiceStub{c}
}

// NewArithServiceStub returns a ArithService stub to handle rpc.Client.
func NewArithServiceStub(c *rpc.Client) ArithService {
    return &rpcArithServiceStub{c}
}

其中生成的服务器端的代码有: ListenAndServeArithService, ServeArithService, RegisterArithService. 生成的客户端的接口有: DialArithService, NewArithServiceClient, NewArithServiceStub. 其中RPC接口对应ArithService接口.

---

编写测试代码

在pbrpc目录创建rpc_server.go文件, 代码如下:

package main

import (
    "encoding/protobuf/proto"
    "errors"

    "./arith.pb"
)

type Arith int

func (t *Arith) Add(args *arith.ArithRequest, reply *arith.ArithResponse) error {
    reply.C = proto.Int32(args.GetA() + args.GetB())
    return nil
}

func (t *Arith) Mul(args *arith.ArithRequest, reply *arith.ArithResponse) error {
    reply.C = proto.Int32(args.GetA() * args.GetB())
    return nil
}

func (t *Arith) Div(args *arith.ArithRequest, reply *arith.ArithResponse) error {
    if args.GetB() == 0 {
        return errors.New("divide by zero")
    }
    reply.C = proto.Int32(args.GetA() / args.GetB())
    return nil
}

func (t *Arith) Error(args *arith.ArithRequest, reply *arith.ArithResponse) error {
    return errors.New("ArithError")
}

func main() {
    arith.ListenAndServeArithService("tcp", ":1234", new(Arith))
}

最关键的是arith.ListenAndServeArithService("tcp", ":1234", new(Arith)). 当然, 也可以使用RegisterArithService或ServeArithService等接口进行定制.

然后在pbrpc创建rpc_client.go对应客户端, 代码如下:

package main

import (
    "encoding/protobuf/proto"
    "log"

    "./arith.pb"
)

func main() {
    // client
    client, stub, err := arith.DialArithService("tcp", "127.0.0.1:1234")
    if err != nil {
        log.Fatalf(`arith.DialArithService("tcp", "127.0.0.1:1234"): %v`, err)
    }
    defer client.Close()

    var args arith.ArithRequest
    var reply arith.ArithResponse

    // Add
    args.A = proto.Int32(1)
    args.B = proto.Int32(2)
    if err = stub.Add(&args, &reply); err != nil {
        log.Fatalf(`arith.Add: %v`, err)
    }
    if reply.GetC() != 3 {
        log.Fatalf(`arith.Add: expected = %d, got = %d`, 3, reply.GetC())
    }

    // Mul
    args.A = proto.Int32(2)
    args.B = proto.Int32(3)
    if err = stub.Mul(&args, &reply); err != nil {
        log.Fatalf(`arith.Mul: %v`, err)
    }
    if reply.GetC() != 6 {
        log.Fatalf(`arith.Mul: expected = %d, got = %d`, 6, reply.GetC())
    }

    // Div
    args.A = proto.Int32(13)
    args.B = proto.Int32(5)
    if err = stub.Div(&args, &reply); err != nil {
        log.Fatalf(`arith.Div: %v`, err)
    }
    if reply.GetC() != 2 {
        log.Fatalf(`arith.Div: expected = %d, got = %d`, 2, reply.GetC())
    }

    // Div zero
    args.A = proto.Int32(1)
    args.B = proto.Int32(0)
    if err = stub.Div(&args, &reply); err.Error() != "divide by zero" {
        log.Fatalf(`arith.Error: expected = %s, got = %s`, "divide by zero", err.Error())
    }

    // Error
    args.A = proto.Int32(1)
    args.B = proto.Int32(2)
    if err = stub.Error(&args, &reply); err.Error() != "ArithError" {
        log.Fatalf(`arith.Error: expected = %s, got = %s`, "ArithError", err.Error())
    }

    log.Printf("Done")
}

然后就可以启动服务, 并测试客户端了.