引言
gRPC 是 Google 开发的一个高性能、开源的通用 RPC (Remote Procedure Call, 远程过程调用) 框架，其面向移动和 HTTP/2 设计，并且可以运行在任何环境中。它可以从任何应用程序中调用其他应用程序的方法，无论这些应用程序是在同一个主机上，还是分布在不同的主机上。gRPC 还为开发人员提供了简洁的服务定义框架，使得能够自动化生成客户端和服务器端的代码。
在本篇文章中，我们将探讨如何在 Go 语言环境中使用 gRPC，并解释协议（特别是 Protobuf，也就是 Protocol Buffers）和编码关系。
一、gRPC和Protobuf：定义并传递数据
gRPC 默认使用 Protobuf，这是 Google 的一种轻量级且高效的结构化数据存储格式。Protobuf 在定义服务和消息类型时表现得尤为强大，它能够简单且精确地定义数据结构，并且支持编译成多种语言的代码。
Protobuf 使用 .proto 文件来定义服务接口和消息结构。例如，我们可以定义一个简单的服务 Greeter，它有一个 SayHello 的 RPC 方法，接受一个 HelloRequest 消息，并返回一个 HelloResponse 消息：
syntax = "proto3";
option go_package = "github.com/xiluo/myrpc/pb";
service Greeter {
rpc SayHello (HelloRequest) returns (HelloResponse);
}
message HelloRequest {
string name = 1;
}
message HelloResponse {
string message = 1;
}
在上述代码中，Greeter 是我们定义的服务，SayHello 是服务中的方法，HelloRequest 和 HelloResponse 则是我们定义的消息类型。每个字段都有一个唯一的数字标识，这些数字在 Protobuf 的二进制格式中用来标识字段。
二、从 Protobuf 到 Go：代码生成
安装插件：
代码语言：javascript复制PB_REL="https://github.com/protocolbuffers/protobuf/releases"
curl -LO $PB_REL/download/v3.15.8/protoc-3.15.8-linux-x86_64.zip
unzip protoc-3.15.8-linux-x86_64.zip -d $HOME/.local
export PATH="$PATH:$HOME/.local/bin"
go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.28
go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@v1.2
export PATH="$PATH:$(go env GOPATH)/bin"一旦我们定义了 .proto 文件，我们就可以使用 Protobuf 编译器 protoc 以及 gRPC 的 Go 插件来生成对应的 Go 代码。这会生成我们服务中每个 RPC 方法的接口代码以及每个消息类型的数据结构代码。
cd demomygrpcpb
protoc --go_out=. --go_opt=paths=source_relative
--go-grpc_out=. --go-grpc_opt=paths=source_relative
greeter.proto代码：greeter.pb.go
代码语言：javascript复制// Code generated by protoc-gen-go. DO NOT EDIT.
// versions:
// protoc-gen-go v1.28.1
// protoc v4.23.3
// source: greeter.proto
package pb // 注意这里的包名
import (
protoreflect "google.golang.org/protobuf/reflect/protoreflect"
protoimpl "google.golang.org/protobuf/runtime/protoimpl"
reflect "reflect"
sync "sync"
)
const (
// Verify that this generated code is sufficiently up-to-date.
_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
// Verify that runtime/protoimpl is sufficiently up-to-date.
_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
)
type HelloRequest struct {
state protoimpl.MessageState
sizeCache protoimpl.SizeCache
unknownFields protoimpl.UnknownFields
Name string `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
}
func (x *HelloRequest) Reset() {
*x = HelloRequest{}
if protoimpl.UnsafeEnabled {
mi := &file_greeter_proto_msgTypes[0]
ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
ms.StoreMessageInfo(mi)
}
}
func (x *HelloRequest) String() string {
return protoimpl.X.MessageStringOf(x)
}
func (*HelloRequest) ProtoMessage() {}
func (x *HelloRequest) ProtoReflect() protoreflect.Message {
mi := &file_greeter_proto_msgTypes[0]
if protoimpl.UnsafeEnabled && x != nil {
ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
if ms.LoadMessageInfo() == nil {
ms.StoreMessageInfo(mi)
}
return ms
}
return mi.MessageOf(x)
}
// Deprecated: Use HelloRequest.ProtoReflect.Descriptor instead.
func (*HelloRequest) Descriptor() ([]byte, []int) {
return file_greeter_proto_rawDescGZIP(), []int{0}
}
func (x *HelloRequest) GetName() string {
if x != nil {
return x.Name
}
return ""
}
type HelloResponse struct {
state protoimpl.MessageState
sizeCache protoimpl.SizeCache
unknownFields protoimpl.UnknownFields
Message string `protobuf:"bytes,1,opt,name=message,proto3" json:"message,omitempty"`
}
func (x *HelloResponse) Reset() {
*x = HelloResponse{}
if protoimpl.UnsafeEnabled {
mi := &file_greeter_proto_msgTypes[1]
ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
ms.StoreMessageInfo(mi)
}
}
func (x *HelloResponse) String() string {
return protoimpl.X.MessageStringOf(x)
}
func (*HelloResponse) ProtoMessage() {}
func (x *HelloResponse) ProtoReflect() protoreflect.Message {
mi := &file_greeter_proto_msgTypes[1]
if protoimpl.UnsafeEnabled && x != nil {
ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
if ms.LoadMessageInfo() == nil {
ms.StoreMessageInfo(mi)
}
return ms
}
return mi.MessageOf(x)
}
// Deprecated: Use HelloResponse.ProtoReflect.Descriptor instead.
func (*HelloResponse) Descriptor() ([]byte, []int) {
return file_greeter_proto_rawDescGZIP(), []int{1}
}
func (x *HelloResponse) GetMessage() string {
if x != nil {
return x.Message
}
return ""
}
var File_greeter_proto protoreflect.FileDescriptor
var file_greeter_proto_rawDesc = []byte{
0x0a, 0x0d, 0x67, 0x72, 0x65, 0x65, 0x74, 0x65, 0x72, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x22,
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0x65, 0x72, 0x76, 0x65, 0x72, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
}
var (
file_greeter_proto_rawDescOnce sync.Once
file_greeter_proto_rawDescData = file_greeter_proto_rawDesc
)
func file_greeter_proto_rawDescGZIP() []byte {
file_greeter_proto_rawDescOnce.Do(func() {
file_greeter_proto_rawDescData = protoimpl.X.CompressGZIP(file_greeter_proto_rawDescData)
})
return file_greeter_proto_rawDescData
}
var file_greeter_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
var file_greeter_proto_goTypes = []interface{}{
(*HelloRequest)(nil), // 0: HelloRequest
(*HelloResponse)(nil), // 1: HelloResponse
}
var file_greeter_proto_depIdxs = []int32{
0, // 0: Greeter.SayHello:input_type -> HelloRequest
1, // 1: Greeter.SayHello:output_type -> HelloResponse
1, // [1:2] is the sub-list for method output_type
0, // [0:1] is the sub-list for method input_type
0, // [0:0] is the sub-list for extension type_name
0, // [0:0] is the sub-list for extension extendee
0, // [0:0] is the sub-list for field type_name
}
func init() { file_greeter_proto_init() }
func file_greeter_proto_init() {
if File_greeter_proto != nil {
return
}
if !protoimpl.UnsafeEnabled {
file_greeter_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
switch v := v.(*HelloRequest); i {
case 0:
return &v.state
case 1:
return &v.sizeCache
case 2:
return &v.unknownFields
default:
return nil
}
}
file_greeter_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
switch v := v.(*HelloResponse); i {
case 0:
return &v.state
case 1:
return &v.sizeCache
case 2:
return &v.unknownFields
default:
return nil
}
}
}
type x struct{}
out := protoimpl.TypeBuilder{
File: protoimpl.DescBuilder{
GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
RawDescriptor: file_greeter_proto_rawDesc,
NumEnums: 0,
NumMessages: 2,
NumExtensions: 0,
NumServices: 1,
},
GoTypes: file_greeter_proto_goTypes,
DependencyIndexes: file_greeter_proto_depIdxs,
MessageInfos: file_greeter_proto_msgTypes,
}.Build()
File_greeter_proto = out.File
file_greeter_proto_rawDesc = nil
file_greeter_proto_goTypes = nil
file_greeter_proto_depIdxs = nil
}
代码：greeter_grpc.pb.go
代码语言：javascript复制// Code generated by protoc-gen-go-grpc. DO NOT EDIT.
// versions:
// - protoc-gen-go-grpc v1.2.0
// - protoc v4.23.3
// source: greeter.proto
package pb
import (
context "context"
grpc "google.golang.org/grpc"
codes "google.golang.org/grpc/codes"
status "google.golang.org/grpc/status"
)
// This is a compile-time assertion to ensure that this generated file
// is compatible with the grpc package it is being compiled against.
// Requires gRPC-Go v1.32.0 or later.
const _ = grpc.SupportPackageIsVersion7
// GreeterClient is the client API for Greeter service.
//
// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
type GreeterClient interface {
SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloResponse, error)
}
type greeterClient struct {
cc grpc.ClientConnInterface
}
func NewGreeterClient(cc grpc.ClientConnInterface) GreeterClient {
return &greeterClient{cc}
}
func (c *greeterClient) SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloResponse, error) {
out := new(HelloResponse)
err := c.cc.Invoke(ctx, "/Greeter/SayHello", in, out, opts...)
if err != nil {
return nil, err
}
return out, nil
}
// GreeterServer is the server API for Greeter service.
// All implementations must embed UnimplementedGreeterServer
// for forward compatibility
type GreeterServer interface {
SayHello(context.Context, *HelloRequest) (*HelloResponse, error)
mustEmbedUnimplementedGreeterServer()
}
// UnimplementedGreeterServer must be embedded to have forward compatible implementations.
type UnimplementedGreeterServer struct {
}
func (UnimplementedGreeterServer) SayHello(context.Context, *HelloRequest) (*HelloResponse, error) {
return nil, status.Errorf(codes.Unimplemented, "method SayHello not implemented")
}
func (UnimplementedGreeterServer) mustEmbedUnimplementedGreeterServer() {}
// UnsafeGreeterServer may be embedded to opt out of forward compatibility for this service.
// Use of this interface is not recommended, as added methods to GreeterServer will
// result in compilation errors.
type UnsafeGreeterServer interface {
mustEmbedUnimplementedGreeterServer()
}
func RegisterGreeterServer(s grpc.ServiceRegistrar, srv GreeterServer) {
s.RegisterService(&Greeter_ServiceDesc, srv)
}
func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
in := new(HelloRequest)
if err := dec(in); err != nil {
return nil, err
}
if interceptor == nil {
return srv.(GreeterServer).SayHello(ctx, in)
}
info := &grpc.UnaryServerInfo{
Server: srv,
FullMethod: "/Greeter/SayHello",
}
handler := func(ctx context.Context, req interface{}) (interface{}, error) {
return srv.(GreeterServer).SayHello(ctx, req.(*HelloRequest))
}
return interceptor(ctx, in, info, handler)
}
// Greeter_ServiceDesc is the grpc.ServiceDesc for Greeter service.
// It's only intended for direct use with grpc.RegisterService,
// and not to be introspected or modified (even as a copy)
var Greeter_ServiceDesc = grpc.ServiceDesc{
ServiceName: "Greeter",
HandlerType: (*GreeterServer)(nil),
Methods: []grpc.MethodDesc{
{
MethodName: "SayHello",
Handler: _Greeter_SayHello_Handler,
},
},
Streams: []grpc.StreamDesc{},
Metadata: "greeter.proto",
}三、实现 gRPC 服务
在 Go 中，实现 gRPC 服务涉及创建一个服务对象并注册到 gRPC 服务器，然后在指定端口启动这个服务器。这个服务对象是我们实现的服务接口，它定义了我们的业务逻辑。例如，我们可以这样实现 Greeter 服务：
package main
import (
context "context"
"demo/mygrpc/pb"
"log"
"net"
grpc "google.golang.org/grpc"
)
type server struct {
// 可以在这里添加其他字段
pb.UnimplementedGreeterServer
}
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloResponse, error) {
return &pb.HelloResponse{Message: "Hello " in.Name}, nil
}
func main() {
// 创建并启动 gRPC 服务器
lis, err := net.Listen("tcp", ":50051")
if err != nil {
log.Fatalf("failed to listen: %v", err)
}
grpcServer := grpc.NewServer()
// 注册服务
greeterServer := &server{}
pb.RegisterGreeterServer(grpcServer, greeterServer)
// 开始接收请求
if err := grpcServer.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
}
}四、创建 gRPC 客户端
在 Go 中创建一个 gRPC 客户端涉及连接到 gRPC 服务器，并通过这个连接创建一个客户端对象，这个对象提供我们服务的方法。例如，我们可以这样创建 Greeter 服务的客户端：
package main
import (
"context"
"demo/mygrpc/pb"
"log"
"time"
"google.golang.org/grpc"
)
func main() {
conn, err := grpc.Dial(":50051", grpc.WithInsecure())
if err != nil {
log.Fatalf("did not connect: %v", err)
}
defer conn.Close()
client := pb.NewGreeterClient(conn)
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
r, err := client.SayHello(ctx, &pb.HelloRequest{Name: "world"})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
log.Printf("Greeting: %s", r.GetMessage())
}
运行测试：
项目结构：
demomygrpcserver> go run .
demomygrpcclient> go run .
2023/07/05 22:24:50 Greeting: Hello world结论
以上就是 gRPC 在 Go 中的基本使用方法。我们使用 Protobuf 定义了服务和消息类型，然后生成了 Go 代码，并实现了服务和客户端。需要注意的是，gRPC 有很多高级功能，比如支持多种 API 设计（一对一，一对多，多对一，多对多），拦截器，流量控制，负载均衡等等，这些都是值得深入研究的主题。
