在使用grpc的時候遇到了一個問題: 如何設置client端的超時時間? 網上搜了一大圈, 沒有太明顯的例子.
這里我們先看下看看grpc的helloworld例子:
client
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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) }
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稍微跟一下SayHello的調用, 最后是調用到invoke函數:
google.golang.org/grpc/call.go
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func invoke(ctx context.Context, method string, args, reply interface{}, cc *ClientConn, opts ...CallOption) (e error) { c := defaultCallInfo mc := cc.GetMethodConfig(method) if mc.WaitForReady != nil { c.failFast = !*mc.WaitForReady } // 值得注意 if mc.Timeout != nil && *mc.Timeout >= 0 { var cancel context.CancelFunc ctx, cancel = context.WithTimeout(ctx, *mc.Timeout) defer cancel() } opts = append(cc.dopts.callOptions, opts...) for _, o := range opts { if err := o.before(&c); err != nil { return toRPCErr(err) } } defer func() { for _, o := range opts { o.after(&c) } }()
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這里值得注意的是context的超時設置. 仔細讀下context的文檔, 會發現context里面有對應的超時設置:
WithTimeout
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package main import ( "context" "fmt" "time" ) func main() { // Pass a context with a timeout to tell a blocking function that it // should abandon its work after the timeout elapses. ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond) defer cancel() select { case <-time.After(1 * time.Second): fmt.Println("overslept") case <-ctx.Done(): fmt.Println(ctx.Err()) // prints "context deadline exceeded" } }
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我們嘗試在client調用之前設置context的超時:
client
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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] } // 改一下 ctx, cancel := context.WithTimeout(context.Background(), 100 * time.Millisecond) 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.Message) }
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為保證超時, 在sever代碼中休息一會兒:
server
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// SayHello implements helloworld.GreeterServer func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) { time.Sleep(1 * time.Second) return &pb.HelloReply{Message: "Hello " + in.Name}, nil }
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分別運行client和server兩個程序, 會看見client端打印:
1
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could not greet: rpc error: code = DeadlineExceeded desc = context deadline exceeded
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