rpc 声明
- helloworld.proto
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;
}
protoc会根据.proto文件生成rpc的客户端和服务端，在*_grpc.pb.go文件中。
- helloworld_grpc.pb.go
其中根据service Greeter定义:
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
}
生成两个接口：
// 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 {
// Sends a greeting
SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error)
}
// GreeterServer is the server API for Greeter service.
// All implementations must embed UnimplementedGreeterServer
// for forward compatibility
type GreeterServer interface {
// Sends a greeting
SayHello(context.Context, *HelloRequest) (*HelloReply, error)
mustEmbedUnimplementedGreeterServer()
}
客户端实现
客户端需要使用使用GreeterClient接口:
- client/main.go
// Package main implements a client for Greeter service.
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()
// 调用_rpc.pb.go中生成代码, 初始化client
c := pb.NewGreeterClient(conn)
// Contact the server and print out its response.
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
// 调用_rpc.pb.go中生成代码, 调用client方法
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())
}
- helloworld.proto
type greeterClient struct {
cc grpc.ClientConnInterface
}
func NewGreeterClient(cc grpc.ClientConnInterface) GreeterClient {
return &greeterClient{cc}
}
r, err := c.SayHello(ctx, &pb.HelloRequest{Name: *name})调用下面的方法
func (c *greeterClient) SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error) {
out := new(HelloReply)
// 委托给cc grpc.ClientConnInterface去进行远程rpc调用
// in: 输入参数，HelloRequest会进行protobuf 序列化， 传送给服务端
// out: 服务端响应会被反序列化为HelloReply
err := c.cc.Invoke(ctx, "/helloworld.Greeter/SayHello", in, out, opts...)
if err != nil {
return nil, err
}
return out, nil
}
服务端实现
rpc SayHello的当然是开发者需要实现的， rpc的其他具体细节则由代码生成。
- server/main.go
// Package main implements a server for Greeter service.
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()
// 注册SayHello服务
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)
}
}
-
helloworld_grpc.pb.go
pb.RegisterGreeterServer(s, &server{})
func RegisterGreeterServer(s grpc.ServiceRegistrar, srv GreeterServer) {
// + 进入rpc实现层
s.RegisterService(&Greeter_ServiceDesc, srv)
}
// SayHello对应的Handler实现
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 {
// 调用服务端的sayHello实现
return srv.(GreeterServer).SayHello(ctx, in)
}
// ...
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: "helloworld.Greeter",
HandlerType: (*GreeterServer)(nil),
// 当Client调用SayHello时，使用_Greeter_SayHello_Handler处理
Methods: []grpc.MethodDesc{
{
MethodName: "SayHello",
Handler: _Greeter_SayHello_Handler,
},
},
Streams: []grpc.StreamDesc{},
Metadata: "examples/helloworld/helloworld/helloworld.proto",
}
s.RegisterService(&Greeter_ServiceDesc, srv)
// ServiceRegistrar wraps a single method that supports service registration. It
// enables users to pass concrete types other than grpc.Server to the service
// registration methods exported by the IDL generated code.
type ServiceRegistrar interface {
// RegisterService registers a service and its implementation to the
// concrete type implementing this interface. It may not be called
// once the server has started serving.
// desc describes the service and its methods and handlers. impl is the
// service implementation which is passed to the method handlers.
RegisterService(desc *ServiceDesc, impl interface{})
}
// RegisterService registers a service and its implementation to the gRPC
// server. It is called from the IDL generated code. This must be called before
// invoking Serve. If ss is non-nil (for legacy code), its type is checked to
// ensure it implements sd.HandlerType.
func (s *Server) RegisterService(sd *ServiceDesc, ss interface{}) {
if ss != nil {
ht := reflect.TypeOf(sd.HandlerType).Elem() // => GreeterServer
st := reflect.TypeOf(ss) // => server
// 检查server是否实现了GreeterServer接口
if !st.Implements(ht) {
logger.Fatalf("grpc: Server.RegisterService found the handler of type %v that does not satisfy %v", st, ht)
}
}
s.register(sd, ss)
}
s.register(sd, ss)
func (s *Server) register(sd *ServiceDesc, ss interface{}) {
s.mu.Lock()
defer s.mu.Unlock()
s.printf("RegisterService(%q)", sd.ServiceName)
// 服务注册必须在服务启动前
if s.serve {
logger.Fatalf("grpc: Server.RegisterService after Server.Serve for %q", sd.ServiceName)
}
// 查重
if _, ok := s.services[sd.ServiceName]; ok {
logger.Fatalf("grpc: Server.RegisterService found duplicate service registration for %q", sd.ServiceName)
}
// 注册到Map methods中
info := &serviceInfo{
serviceImpl: ss,
methods: make(map[string]*MethodDesc),
streams: make(map[string]*StreamDesc),
mdata: sd.Metadata,
}
for i := range sd.Methods {
d := &sd.Methods[i]
info.methods[d.MethodName] = d
}
for i := range sd.Streams {
d := &sd.Streams[i]
info.streams[d.StreamName] = d
}
s.services[sd.ServiceName] = info
}
