從零開始搭建 gRPC 服務 - Golang 篇(二)
在從零開始搭建 gRPC 服務 - Golang 篇(一)中介紹瞭如何搭建 gRPC
環境並構建一個簡單的 gRPC
服務,本文將介紹 gRPC
的 streaming
。
流式 RPC
gRPC
基於標準的 HTTP/2 進行傳輸,可以方便的實現 streaming
功能。要在 gRPC
中使用 streaming
,只需要在 proto
中在請求或響應前加上 stream
即可。
服務端流式 RPC:Server-side streaming RPC
客戶端向伺服器傳送請求並獲取流以讀取訊息序列;客戶端從返回的流中讀取,直到沒有更多訊息; gRPC 保證單個 RPC 呼叫中的訊息排序。
在從零開始搭建 gRPC 服務 - Golang 篇(一)中的 helloworld.proto
中增加介面 LotsOfReplies
:
syntax = "proto3"; option go_package = "github.com/grpc/example/helloworld"; package helloworld; // The greeting service definition. service Greeter { rpc LotsOfReplies (HelloRequest) returns (stream 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; }
編譯 .proto
檔案
$ protoc helloworld.proto --go_out=output
$ tree .
.
├── helloworld.proto
└── output
└── github.com
└── grpc
└── example
└── helloworld
└── helloworld.pb.go
5 directories, 2 files
此時生成的程式碼就已經包含了流的處理,在使用上需要注意:伺服器端程式碼的實現要通過流的方式傳送響應。
編寫 server.go
package main
import (
"context"
"fmt"
"log"
"net"
"google.golang.org/grpc"
pb "./output/github.com/grpc/example/helloworld"
"google.golang.org/grpc/reflection"
)
const (
port = ":50051"
)
// server is used to implement helloworld.GreeterServer.
type server struct{}
func (s *server) LotsOfReplies(in *pb.HelloRequest, stream pb.Greeter_LotsOfRepliesServer) error {
for idx := 0; idx < 10; idx ++ {
stream.Send(&pb.HelloReply{Message: fmt.Sprintf("Hello %s %d", in.Name, idx)})
}
return 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{})
// Register reflection service on gRPC server.
reflection.Register(s)
if err := s.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
}
}
如上程式碼所示,服務端在接收到請求後通過 stream 返回了 10 個響應。
編寫 client.go
package main
import (
"context"
"io"
"log"
"os"
"time"
"google.golang.org/grpc"
pb "./output/github.com/grpc/example/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]
}
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
stream, err := c.LotsOfReplies(ctx, &pb.HelloRequest{Name: name})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
for {
reply, err := stream.Recv()
if err == io.EOF {
break
}
if err != nil {
log.Fatalf("%v.LotsOfReplies() = _, %v", c, err)
}
log.Printf("Greeting: %s\n", reply.Message)
}
}
客戶端從 stream 中讀取到若干響應,直到讀到 EOF 結束。
執行 gRPC
服務
開啟兩個會話視窗,在其中之一執行:
$ go run server.go
在另一個會話視窗執行:
$ go run client.go gRPC_stream
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 0
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 1
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 2
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 3
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 4
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 5
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 6
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 7
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 8
2018/12/23 21:31:38 Greeting: Hello gRPC_stream 9
客戶端流式 RPC:Client-side streaming RPC
客戶端再次使用提供的流寫入一系列訊息並將其傳送到伺服器;一旦客戶端寫完訊息,它就等待伺服器讀取它們並返回它的響應; gRPC 保證在單個 RPC 呼叫中的訊息排序。
改寫 helloworld.proto
,增加 LotsOfGreetings
:
syntax = "proto3";
option go_package = "github.com/grpc/example/helloworld";
package helloworld;
// The greeting service definition.
service Greeter {
rpc LotsOfGreetings (stream HelloRequest) returns (HelloReply) {}
}
// The request message containing the user's name.
message HelloRequest {
string name = 1;
int32 index = 2;
}
// The response message containing the greetings
message HelloReply {
string message = 1;
}
編寫 server.go
package main
import (
"context"
"fmt"
"io"
"log"
"net"
"google.golang.org/grpc"
pb "./output/github.com/grpc/example/helloworld"
"google.golang.org/grpc/reflection"
)
const (
port = ":50051"
)
// server is used to implement helloworld.GreeterServer.
type server struct{}
func (s *server) LotsOfGreetings(stream pb.Greeter_LotsOfGreetingsServer) error {
var total int32
var name string
for {
greeting, err := stream.Recv()
if err == io.EOF {
return stream.SendAndClose(&pb.HelloReply{
Message: fmt.Sprintf("Hello %s, total %d", name, total),
})
}
if err != nil {
return err
}
name = greeting.Name
total += greeting.Index
}
return 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{})
// Register reflection service on gRPC server.
reflection.Register(s)
if err := s.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
}
}
服務端通過 stream 接收到若干請求,直到讀到 EOF 後再返回響應。
編寫 client.go
package main
import (
"context"
"log"
"os"
"time"
"google.golang.org/grpc"
pb "./output/github.com/grpc/example/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]
}
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
stream, err := c.LotsOfGreetings(ctx)
if err != nil {
log.Fatalf("could not greet: %v", err)
}
for idx := 0; idx < 10; idx ++ {
if err := stream.Send(&pb.HelloRequest{
Name: name,
Index: int32(idx),
}); err != nil {
log.Fatalf("send err: %v", err)
}
}
reply, err := stream.CloseAndRecv()
if err != nil {
log.Fatalf("%v.CloseAndRecv() got error %v, want %v", stream, err, nil)
}
log.Printf("Greeting: %s\n", reply.Message)
}
客戶端通過 stream 發起 10 個請求,然後關閉 stream 並接收響應。
執行 gRPC
服務
開啟兩個會話視窗,在其中之一執行:
$ go run server.go
在另一個會話視窗執行:
$ go run client.go gRPC_stream
2018/12/23 22:06:43 Greeting: Hello gRPC_stream, total 45
雙向流式 RPC:Bidirectional streaming RPC
雙方使用讀寫流傳送一系列訊息,這兩個流獨立執行,因此客戶端和伺服器可以按照他們喜歡的順序進行讀寫:例如伺服器可以在寫入響應之前等待接收所有客戶端訊息,或者它可以交替讀取訊息然後寫入訊息,或其他一些讀寫組合;gRPC 保證在單個 RPC 呼叫中的訊息排序。
改寫 helloworld.proto
,增加 BidiHello
:
syntax = "proto3";
option go_package = "github.com/grpc/example/helloworld";
package helloworld;
// The greeting service definition.
service Greeter {
rpc BidiHello(stream HelloRequest) returns (stream HelloReply) {}
}
// The request message containing the user's name.
message HelloRequest {
string name = 1;
int32 index = 2;
}
// The response message containing the greetings
message HelloReply {
string message = 1;
}
編寫 server.go
package main
import (
"context"
"fmt"
"io"
"log"
"net"
"strings"
"google.golang.org/grpc"
pb "./output/github.com/grpc/example/helloworld"
"google.golang.org/grpc/reflection"
)
const (
port = ":50051"
)
// server is used to implement helloworld.GreeterServer.
type server struct{}
func (s *server) BidiHello(stream pb.Greeter_BidiHelloServer) error {
for {
in, err := stream.Recv()
if err == io.EOF {
return nil
}
if err != nil {
return err
}
message := strings.Replace(in.Name, "嗎", "", -1)
message = strings.Replace(message, "?", "!", -1)
err = stream.Send(&pb.HelloReply{Message: message})
if err != nil {
return err
}
}
return 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{})
// Register reflection service on gRPC server.
reflection.Register(s)
if err := s.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
}
}
服務端從 stream 中讀取到請求後立即返回。
編寫 client.go
package main
import (
"context"
"fmt"
"log"
"io"
"time"
"google.golang.org/grpc"
pb "./output/github.com/grpc/example/helloworld"
)
const (
address = "localhost:50051"
)
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)
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
stream, err := c.BidiHello(ctx)
if err != nil {
log.Fatalf("%v.BidiHello(_) = _, %v", c, err)
}
waitc := make(chan struct{})
go func() {
for {
in, err := stream.Recv()
if err == io.EOF {
// read done.
close(waitc)
return
}
if err != nil {
log.Fatalf("Failed to receive a note : %v", err)
}
fmt.Printf("AI: %s\n", in.Message)
}
}()
for {
request := &pb.HelloRequest{}
fmt.Scanln(&request.Name)
if request.Name == "quit" {
break
}
if err := stream.Send(request); err != nil {
log.Fatalf("Failed to send a req: %v", err)
}
}
stream.CloseSend()
<-waitc
}
客戶端從標準輸出接收輸入,然後通過 stream 傳送請求,另一個 goroutine
則不斷從 stream 中接收響應。
執行 gRPC
服務
開啟兩個會話視窗,在其中之一執行:
$ go run server.go
在另一個會話視窗執行:
$ go run client.go
在嗎?
AI: 在!
你好
AI: 你好
能聽懂漢語嗎?
AI: 能聽懂漢語!
真的嗎?
AI: 真的!
quit