不知道从什么时候开始，使用gRPC成为编写C-S程序的新潮流，就连etcd v3也使用gRPC。
一方面，使用gRPC可以大大简化Client与Server的消息封装以及API的实现，这两者是非常琐碎的事情；另一方面，gRPC使用protobuf及HTTP2，性能相对于传统的JSON，性能有一些优势。
Install gRPC
Use the following command to install gRPC.
$ go version
go version go1.5.1 darwin/amd64
$ go get google.golang.org/grpc
Install Protocol Buffers v3 compiler, which is used to generate gRPC service code.
$ wget https://github.com/google/protobuf/releases/download/v3.1.0/protoc-3.1.0-osx-x86_64.zip
$ unzip protoc-3.1.0-osx-x86_64.zip
$ bin/protoc --version
libprotoc 3.1.0
Install the protoc plugin for Go.
$ go get -u github.com/golang/protobuf/{proto,protoc-gen-go}
$ ls $GOPATH/bin
protoc-gen-go
Try helloworld
$ cd $GOPATH/src/google.golang.org/grpc/examples/helloworld
helloworld/helloworld.proto
syntax = "proto3";
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;
}
Run server and client:
$ go run greeter_server/main.go
$ go run greeter_client/main.go
2016/10/31 20:12:27 Greeting: Hello world
Update gRPC service
helloworld/helloworld.proto增加SayHelloAgain方法:
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
// Sends another greeting
rpc SayHelloAgain (HelloRequest) returns (HelloReply) {}
}
...
生成新的helloworld/helloworld.pb.go:
$ protoc -I helloworld/ helloworld/helloworld.proto --go_out=plugins=grpc:helloworld
Update the server:
greeter_server/main.go增加新的SayHelloAgain的实现:
package main
import (
"log"
"net"
"golang.org/x/net/context"
"google.golang.org/grpc"
pb "google.golang.org/grpc/examples/helloworld/helloworld"
)
const (
port = ":50051"
)
// server is used to implement helloworld.GreeterServer.
type server struct{}
// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
return &pb.HelloReply{Message: "Hello " + in.Name}, nil
}
func (s *server) SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
return &pb.HelloReply{Message: "Hello again " + in.Name}, nil
}
func main() {
lis, err := net.Listen("tcp", port)
if err != nil {
log.Fatalf("failed to listen: %v", err)
}
s := grpc.NewServer()
pb.RegisterGreeterServer(s, &server{})
if err := s.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
}
}
Update the client:
greeter_client/main.go增加对SayHelloAgain的调用:
import (
"log"
"os"
"golang.org/x/net/context"
"google.golang.org/grpc"
pb "google.golang.org/grpc/examples/helloworld/helloworld"
)
const (
address = "localhost:50051"
defaultName = "world"
)
func main() {
// Set up a connection to the server.
conn, err := grpc.Dial(address, grpc.WithInsecure())
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.
name := defaultName
if len(os.Args) > 1 {
name = os.Args[1]
}
r, err := c.SayHello(context.Background(), &pb.HelloRequest{Name: name})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
log.Printf("Greeting: %s", r.Message)
r, err = c.SayHelloAgain(context.Background(), &pb.HelloRequest{Name: name})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
log.Printf("Greeting: %s", r.Message)
}
Run it:
$ go run greeter_client/main.go
2016/11/01 09:45:46 Greeting: Hello world
2016/11/01 09:45:46 Greeting: Hello again world