In use grpc time encountered a problem: how to set the timeout client-side Internet search a large circle, not too obvious example?.
Here we look at look at the helloworld example grpc:
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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With a little bit SayHelloof calls, and finally the call to invokethe function:
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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It is worth noting that context timeout setting carefully read the document under the context of, you will find there are corresponding context timeout setting:
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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We try to set the context of a timeout before the client calls:
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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In order to ensure a timeout, a break in the sever code:
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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Two were running client and server programs, you will see client-side printing:
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could not greet: rpc error: code = DeadlineExceeded desc = context deadline exceeded
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