如果您最近有学习 gRPC 如何使用的打算，那么您第一步其实应该学习 Protocol Buffers。
废话不多说，我们开始学习：
一、定义消息
1、首先看一个简单的例子：
1 syntax = "proto3"; 2 3 message SearchRequest { 4 string query = 1; 5 int32 page_number = 2; 6 int32 result_per_page = 3; 7 }
第一行 syntax 用于声明版本，如果不声明则默认使用版本2。
第三行 message 用于声明消息结构体。
第四到第六行每个字段后面都有一个数值，用于标识消息在二进制格式中的位置。值从1到15采用1个字节编码。
值从16到2047采用两个字节编码，最小的值是1，最大的值是2的29次方减1，另外19000到19999你也不可以使用，这些是保留值。
1 message SearchRequest { 2 string query = 1; 3 int32 page_number = 2; 4 int32 result_per_page = 3; 5 } 6 7 message SearchResponse { 8 ... 9 }
另外，多个消息类型是可以定义在一个以 .proto 为后缀的文件的，如果你想要添加注释的话，同注释代码一样。
值得注意的是，如果您要修改消息类型，比如删除字段，或者注释字段，那么以后有可能有人在你删除字段的位置添加了一个新字段，并使用原删除字段相同的数值编号。如果此时有别的服务还在使用老版本的话，那么会导致数据被破坏。此时你可以使用 reserved 关键字来预占编号或者预占字段名称，如下所示：
message Foo { reserved 2, 15, 9 to 11, 40 to max; reserved "foo", "bar"; }
另外，在同一个 reserved 语句中不能同时预占编号和字段名称。
2、Protocol Buffers 同样支持枚举与结构嵌套。
enum Corpus { CORPUS_UNSPECIFIED = 0; CORPUS_UNIVERSAL = 1; CORPUS_WEB = 2; CORPUS_IMAGES = 3; CORPUS_LOCAL = 4; CORPUS_NEWS = 5; CORPUS_PRODUCTS = 6; CORPUS_VIDEO = 7; } message SearchRequest { string query = 1; int32 page_number = 2; int32 result_per_page = 3; Corpus corpus = 4; }
枚举的第一个值为0，另外也支持键值对类型 map<key_type, value_type> map_field = N;
3、再来看另外一个语句
message SearchResponse { repeated Result results = 1; } message Result { optional string url = 1; string title = 2; repeated string snippets = 3; }
optional 关键字
字面意思是可选的意思，具体protobuf里面怎么处理这个字段呢，就是protobuf处理的时候另外加了一个bool的变量，用来标记这个optional字段是否有值，发送方在发送的时候，如果这个字段有值，那么就给bool变量标记为true，否则就标记为false，接收方在收到这个字段的同时，也会收到发送方同时发送的bool变量，拿着bool变量就知道这个字段是否有值了，这就是option的意思。
repeated 关键字
字面意思大概是重复的意思，其实protobuf处理这个字段的时候，也是optional字段一样，另外加了一个count计数变量，用于标明这个字段有多少个，这样发送方发送的时候，同时发送了count计数变量和这个字段的起始地址，接收方在接受到数据之后，按照count来解析对应的数据即可。
4、导入
如果你想导入别的 proto 文件里的消息类型，同样也可以使用 import 导入：
import "myproject/other_protos.proto";
默认情况下，只能使用直接导入的 .proto 文件中的定义。然而，有时您可能需要将 .proto 文件移动到新的位置。您可以在旧位置放置一个占位符的.proto文件，使用 import public 将所有导入转发到新位置，而不是直接移动 .proto 文件并在一次更改中更新所有调用站点。
5、包
您可以向.proto文件添加可选的包说明符，以防止协议消息类型之间的名称冲突。
package foo.bar; message Open { ... }
message Foo { ... foo.bar.Open open = 1; ... }
为了生成Go代码，可以为提供编译后的输出路径。
option go_package = "example.com/project/protos/fizz";
二、定义服务
如果您想在RPC(远程过程调用)系统中使用您的消息类型，您可以在 .proto 文件中定义RPC服务接口，protocol buffer compiler将用您选择的语言生成服务接口代码。因此，如果你想用一个方法定义一个RPC服务，它接受你的SearchRequest并返回一个SearchResponse，你可以在你的 .proto 文件中定义它，如下所示:
service SearchService { rpc Search(SearchRequest) returns (SearchResponse); }
三、编译 protocol buffer
现在运行编译器，指定源目录(应用程序源代码所在的目录-如果不提供值，则使用当前目录)和目标目录(您希望生成的代码存放的目录;通常与$SRC_DIR相同)，以及你的 .proto 的路径。在这种情况下，您将调用:
protoc -I=$SRC_DIR --go_out=$DST_DIR $SRC_DIR/addressbook.proto
假如您输入以下命令进行编译，并且 proto 文件使用了 option go_package = "/path2";
protoc --go_out=./path1 ./test.proto
那么输出目录就在当前目录的 /path1/paht2 目录下。
举个例子：
syntax = "proto3"; package test; option go_package = "order/service"; message SearchRequest { string requestParam1 = 1; string requestParam2 = 2; int32 requestParam3 = 3; } message SearchResponse { int32 code = 1; string msg = 2; } service SearchService { rpc SearchOrder(SearchRequest) returns (SearchResponse); }
使用如下命令进行编译：
protoc --go_out=./gen ./test.proto
编译之后的文件在 ./gen/order/service/ 目录下，文件名为 test.pb.go:
// Code generated by protoc-gen-go. DO NOT EDIT. // versions: // protoc-gen-go v1.28.1 // protoc v4.22.0 // source: test.proto package service 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 SearchRequest struct { state protoimpl.MessageState sizeCache protoimpl.SizeCache unknownFields protoimpl.UnknownFields RequestParam1 string `protobuf:"bytes,1,opt,name=requestParam1,proto3" json:"requestParam1,omitempty"` RequestParam2 string `protobuf:"bytes,2,opt,name=requestParam2,proto3" json:"requestParam2,omitempty"` RequestParam3 int32 `protobuf:"varint,3,opt,name=requestParam3,proto3" json:"requestParam3,omitempty"` } func (x *SearchRequest) Reset() { *x = SearchRequest{} if protoimpl.UnsafeEnabled { mi := &file_test_proto_msgTypes[0] ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x)) ms.StoreMessageInfo(mi) } } func (x *SearchRequest) String() string { return protoimpl.X.MessageStringOf(x) } func (*SearchRequest) ProtoMessage() {} func (x *SearchRequest) ProtoReflect() protoreflect.Message { mi := &file_test_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 SearchRequest.ProtoReflect.Descriptor instead. func (*SearchRequest) Descriptor() ([]byte, []int) { return file_test_proto_rawDescGZIP(), []int{0} } func (x *SearchRequest) GetRequestParam1() string { if x != nil { return x.RequestParam1 } return "" } func (x *SearchRequest) GetRequestParam2() string { if x != nil { return x.RequestParam2 } return "" } func (x *SearchRequest) GetRequestParam3() int32 { if x != nil { return x.RequestParam3 } return 0 } type SearchResponse struct { state protoimpl.MessageState sizeCache protoimpl.SizeCache unknownFields protoimpl.UnknownFields Code int32 `protobuf:"varint,1,opt,name=code,proto3" json:"code,omitempty"` Msg string `protobuf:"bytes,2,opt,name=msg,proto3" json:"msg,omitempty"` } func (x *SearchResponse) Reset() { *x = SearchResponse{} if protoimpl.UnsafeEnabled { mi := &file_test_proto_msgTypes[1] ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x)) ms.StoreMessageInfo(mi) } } func (x *SearchResponse) String() string { return protoimpl.X.MessageStringOf(x) } func (*SearchResponse) ProtoMessage() {} func (x *SearchResponse) ProtoReflect() protoreflect.Message { mi := &file_test_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 SearchResponse.ProtoReflect.Descriptor instead. func (*SearchResponse) Descriptor() ([]byte, []int) { return file_test_proto_rawDescGZIP(), []int{1} } func (x *SearchResponse) GetCode() int32 { if x != nil { return x.Code } return 0 } func (x *SearchResponse) GetMsg() string { if x != nil { return x.Msg } return "" } var File_test_proto protoreflect.FileDescriptor var file_test_proto_rawDesc = []byte{ 0x0a, 0x0a, 0x74, 0x65, 0x73, 0x74, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x12, 0x04, 0x74, 0x65, 0x73, 0x74, 0x22, 0x81, 0x01, 0x0a, 0x0d, 0x53, 0x65, 0x61, 0x72, 0x63, 0x68, 0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x12, 0x24, 0x0a, 0x0d, 0x72, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x50, 0x61, 0x72, 0x61, 0x6d, 0x31, 0x18, 0x01, 0x20, 0x01, 0x28, 0x09, 0x52, 0x0d, 0x72, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x50, 0x61, 0x72, 0x61, 0x6d, 0x31, 0x12, 0x24, 0x0a, 0x0d, 0x72, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x50, 0x61, 0x72, 0x61, 0x6d, 0x32, 0x18, 0x02, 0x20, 0x01, 0x28, 0x09, 0x52, 0x0d, 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0x74, 0x2e, 0x53, 0x65, 0x61, 0x72, 0x63, 0x68, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x42, 0x0f, 0x5a, 0x0d, 0x6f, 0x72, 0x64, 0x65, 0x72, 0x2f, 0x73, 0x65, 0x72, 0x76, 0x69, 0x63, 0x65, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33, } var ( file_test_proto_rawDescOnce sync.Once file_test_proto_rawDescData = file_test_proto_rawDesc ) func file_test_proto_rawDescGZIP() []byte { file_test_proto_rawDescOnce.Do(func() { file_test_proto_rawDescData = protoimpl.X.CompressGZIP(file_test_proto_rawDescData) }) return file_test_proto_rawDescData } var file_test_proto_msgTypes = make([]protoimpl.MessageInfo, 2) var file_test_proto_goTypes = []interface{}{ (*SearchRequest)(nil), // 0: test.SearchRequest (*SearchResponse)(nil), // 1: test.SearchResponse } var file_test_proto_depIdxs = []int32{ 0, // 0: test.SearchService.SearchOrder:input_type -> test.SearchRequest 1, // 1: test.SearchService.SearchOrder:output_type -> test.SearchResponse 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_test_proto_init() } func file_test_proto_init() { if File_test_proto != nil { return } if !protoimpl.UnsafeEnabled { file_test_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} { switch v := v.(*SearchRequest); i { case 0: return &v.state case 1: return &v.sizeCache case 2: return &v.unknownFields default: return nil } } file_test_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} { switch v := v.(*SearchResponse); 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_test_proto_rawDesc, NumEnums: 0, NumMessages: 2, NumExtensions: 0, NumServices: 1, }, GoTypes: file_test_proto_goTypes, DependencyIndexes: file_test_proto_depIdxs, MessageInfos: file_test_proto_msgTypes, }.Build() File_test_proto = out.File file_test_proto_rawDesc = nil file_test_proto_goTypes = nil file_test_proto_depIdxs = nil }
如果你要使用的消息结构的话，可以看如下示例：
package main import ( "fmt" "github.com/golang/protobuf/proto" pb "study.com/study-user/api/proto/gen/order/service" ) func main() { request := &pb.SearchRequest{ RequestParam1: "aaa", RequestParam2: "bbb", RequestParam3: 0, } fmt.Printf("编码前: %v n", request) marshal, err := proto.Marshal(request) fmt.Printf("编码后: %v n", marshal) if err == nil { newRequest := &pb.SearchRequest{} proto.Unmarshal(marshal, newRequest) fmt.Printf("解码后: %v n", newRequest) } }
细心的你可能发现，我没有调用函数，毕竟也没有定义函数，你就算用 pb. 后面也找不到函数名，可以先看看gRPC，这里会告诉你答案。
四、gRPC介绍
当你来到gRPC官网Go语言时，他会要求你提前准备如下：
1、安装 Go
3、安装编译插件
$ 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
4、配置 Protocol Buffer 环境变量
$ export PATH="$PATH:$(go env GOPATH)/bin"
5、下载测试用例
git clone -b v1.53.0 --depth 1 https://github.com/grpc/grpc-go
6、运行示例
go run greeter_server/main.go go run greeter_client/main.go
6、生成 gRPC代码
$ protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=. --go-grpc_opt=paths=source_relative helloworld/helloworld.proto
这个我们拿之前的例子来举例，go_opt 选项你可以在源文件中使用 option go_package 来替代。
protoc --go_out=./gen --go-grpc_out=./gen ./test.proto
这时可以看到生成了两个文件：test.pb.go、test_grpc.pb.go，我们来看一下生成的 grpc 代码：
// Code generated by protoc-gen-go-grpc. DO NOT EDIT. // versions: // - protoc-gen-go-grpc v1.2.0 // - protoc v4.22.0 // source: test.proto package service 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 // SearchServiceClient is the client API for SearchService 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 SearchServiceClient interface { SearchOrder(ctx context.Context, in *SearchRequest, opts ...grpc.CallOption) (*SearchResponse, error) } type searchServiceClient struct { cc grpc.ClientConnInterface } func NewSearchServiceClient(cc grpc.ClientConnInterface) SearchServiceClient { return &searchServiceClient{cc} } func (c *searchServiceClient) SearchOrder(ctx context.Context, in *SearchRequest, opts ...grpc.CallOption) (*SearchResponse, error) { out := new(SearchResponse) err := c.cc.Invoke(ctx, "/test.SearchService/SearchOrder", in, out, opts...) if err != nil { return nil, err } return out, nil } // SearchServiceServer is the server API for SearchService service. // All implementations must embed UnimplementedSearchServiceServer // for forward compatibility type SearchServiceServer interface { SearchOrder(context.Context, *SearchRequest) (*SearchResponse, error) mustEmbedUnimplementedSearchServiceServer() } // UnimplementedSearchServiceServer must be embedded to have forward compatible implementations. type UnimplementedSearchServiceServer struct { } func (UnimplementedSearchServiceServer) SearchOrder(context.Context, *SearchRequest) (*SearchResponse, error) { return nil, status.Errorf(codes.Unimplemented, "method SearchOrder not implemented") } func (UnimplementedSearchServiceServer) mustEmbedUnimplementedSearchServiceServer() {} // UnsafeSearchServiceServer may be embedded to opt out of forward compatibility for this service. // Use of this interface is not recommended, as added methods to SearchServiceServer will // result in compilation errors. type UnsafeSearchServiceServer interface { mustEmbedUnimplementedSearchServiceServer() } func RegisterSearchServiceServer(s grpc.ServiceRegistrar, srv SearchServiceServer) { s.RegisterService(&SearchService_ServiceDesc, srv) } func _SearchService_SearchOrder_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) { in := new(SearchRequest) if err := dec(in); err != nil { return nil, err } if interceptor == nil { return srv.(SearchServiceServer).SearchOrder(ctx, in) } info := &grpc.UnaryServerInfo{ Server: srv, FullMethod: "/test.SearchService/SearchOrder", } handler := func(ctx context.Context, req interface{}) (interface{}, error) { return srv.(SearchServiceServer).SearchOrder(ctx, req.(*SearchRequest)) } return interceptor(ctx, in, info, handler) } // SearchService_ServiceDesc is the grpc.ServiceDesc for SearchService service. // It's only intended for direct use with grpc.RegisterService, // and not to be introspected or modified (even as a copy) var SearchService_ServiceDesc = grpc.ServiceDesc{ ServiceName: "test.SearchService", HandlerType: (*SearchServiceServer)(nil), Methods: []grpc.MethodDesc{ { MethodName: "SearchOrder", Handler: _SearchService_SearchOrder_Handler, }, }, Streams: []grpc.StreamDesc{}, Metadata: "test.proto", }
我们重点关注如下：
// SearchServiceServer is the server API for SearchService service. // All implementations must embed UnimplementedSearchServiceServer // for forward compatibility type SearchServiceServer interface { SearchOrder(context.Context, *SearchRequest) (*SearchResponse, error) mustEmbedUnimplementedSearchServiceServer() }
SearchServiceServer 是 SearchService 服务的 api，所有的实现必须组合 mustEmbedUnimplementedSearchServiceServer 为了向前兼容。
7、官方helloworld使用示例
proto 文件：
syntax = "proto3"; option go_package = "google.golang.org/grpc/examples/helloworld/helloworld"; option java_multiple_files = true; option java_package = "io.grpc.examples.helloworld"; option java_outer_classname = "HelloWorldProto"; package helloworld; // The greeting service definition. service Greeter { // Sends a greeting rpc SayHello (HelloRequest) returns (HelloReply) {} } // The request message containing the user's name. message HelloRequest { string name = 1; } // The response message containing the greetings message HelloReply { string message = 1; }
服务端：
package main import ( "context" "flag" "fmt" "log" "net" "google.golang.org/grpc" pb "google.golang.org/grpc/examples/helloworld/helloworld" ) var ( port = flag.Int("port", 50051, "The server port") ) // server is used to implement helloworld.GreeterServer. type server struct { pb.UnimplementedGreeterServer } // SayHello implements helloworld.GreeterServer func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) { log.Printf("Received: %v", in.GetName()) return &pb.HelloReply{Message: "Hello " + in.GetName()}, nil } func main() { flag.Parse() lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port)) if err != nil { log.Fatalf("failed to listen: %v", err) } s := grpc.NewServer() pb.RegisterGreeterServer(s, &server{}) log.Printf("server listening at %v", lis.Addr()) if err := s.Serve(lis); err != nil { log.Fatalf("failed to serve: %v", err) } }
官方使用 server 组合了 pb.UnimplementedGreeterServer，然后 server 实现了 SayHello 的方法。
在 main 方法里对某个端口号进行监听，并注册了 SayHello 服务，因为只有一个 rpc 方法，然后服务端进行服务。
客户端：
package main import ( "context" "flag" "log" "time" "google.golang.org/grpc" "google.golang.org/grpc/credentials/insecure" pb "google.golang.org/grpc/examples/helloworld/helloworld" ) const ( defaultName = "world" ) var ( addr = flag.String("addr", "localhost:50051", "the address to connect to") name = flag.String("name", defaultName, "Name to greet") ) func main() { flag.Parse() // Set up a connection to the server. conn, err := grpc.Dial(*addr, grpc.WithTransportCredentials(insecure.NewCredentials())) if err != nil { log.Fatalf("did not connect: %v", err) } defer conn.Close() c := pb.NewGreeterClient(conn) // Contact the server and print out its response. 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: %s", r.GetMessage()) }
客户端连接服务端gRPC服务地址，调用服务端的 SayHello 方法，拿到结果后返回。
如果想要详细了解的话，可以看看 gRPC 官方文档哈，如果有帮助可以帮忙点个赞哈！
