在使用grpc的时候遇到了一个问题: 如何设置client端的超时时间? 网上搜了一大圈, 没有太明显的例子.
这里我们先看下看看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的调用, 最后是调用到invoke函数:
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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这里值得注意的是context的超时设置. 仔细读下context的文档, 会发现context里面有对应的超时设置:
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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我们尝试在client调用之前设置context的超时:
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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为保证超时, 在sever代码中休息一会儿:
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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分别运行client和server两个程序, 会看见client端打印:
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could not greet: rpc error: code = DeadlineExceeded desc = context deadline exceeded
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