请求重试请求重试当一次服务调用失败时，我们可以让框架选择自动重试几次，这样能提高用户侧看到的请求成功率。在 failover cluster 模式下 dubbo-go 支持自动重试。
1.介绍本示例演示如何在 client 端调用失败时配置重试功能，完整示例源码地址
2.如何使用重试功能在使用 client.NewClient() 创建客户端时，可以使用 client.WithClientRetries() 方法设置重试次数。
cli, err := client.NewClient(
client.WithClientURL("tri://127.0.0.1:20000"),
client.WithClientRetries(3),
)
或者，可以使用 client.WithRequestTimeout() 设置服务粒度的超时时间（以下配置对服务 svc 起作用）。
svc, err := greet.NewGreetService(cli, client.WithClientRetries(5))
也可以在调用发起时，使用 client.WithCallRetries() 指定重试次数
resp, err := svc.Greet(context.Background(), &greet.GreetRequest{Name: "hello world"}, client.WithCallRetries(6))
从上往下，以上三种方式的优先级逐步提高，client.WithCallRetries() 指定的重试次数优先级最高。
3.示例解读3.1服务端介绍服务端proto文件源文件路径：dubbo-go-sample/retry/proto/greet.proto
syntax = "proto3";
package greet;
option go_package = "github.com/apache/dubbo-go-samples/retry/proto;greet";
message GreetRequest {
string name = 1;
}
message GreetResponse {
string greeting = 1;
}
service GreetService {
rpc Greet(GreetRequest) returns (GreetResponse) {}
rpc GreetTimeout(GreetRequest) returns (GreetResponse) {}
}
服务端handler文件Greet方法直接响应，GreetRetry方法用于模拟重试。
package main
import (
"context"
"github.com/pkg/errors"
_ "dubbo.apache.org/dubbo-go/v3/imports"
"dubbo.apache.org/dubbo-go/v3/protocol"
"dubbo.apache.org/dubbo-go/v3/server"
greet "github.com/apache/dubbo-go-samples/retry/proto"
"github.com/dubbogo/gost/log/logger"
)
type GreetTripleServer struct {
requestTime int
}
func (srv *GreetTripleServer) Greet(ctx context.Context, req *greet.GreetRequest) (*greet.GreetResponse, error) {
resp := &greet.GreetResponse{Greeting: req.Name}
logger.Info("Not need retry, request success")
return resp, nil
}
func (srv *GreetTripleServer) GreetRetry(ctx context.Context, req *greet.GreetRequest) (*greet.GreetResponse, error) {
if srv.requestTime < 3 {
srv.requestTime++
logger.Infof("retry %d times", srv.requestTime)
return nil, errors.New("retry")
}
resp := &greet.GreetResponse{Greeting: req.Name}
logger.Infof("retry success, current request time is %d", srv.requestTime)
srv.requestTime = 0
return resp, nil
}
func main() {
srv, err := server.NewServer(
server.WithServerProtocol(
protocol.WithPort(20000),
),
)
if err != nil {
panic(err)
}
if err := greet.RegisterGreetServiceHandler(srv, &GreetTripleServer{
requestTime: 0,
}); err != nil {
panic(err)
}
if err := srv.Serve(); err != nil {
logger.Error(err)
}
}
3.2客户端介绍客户端client文件，创建客户端，设置重试次数为3，分别请求Greet和GreetRetry，观察服务端日志输出。
package main
import (
"context"
"dubbo.apache.org/dubbo-go/v3/client"
_ "dubbo.apache.org/dubbo-go/v3/imports"
greet "github.com/apache/dubbo-go-samples/retry/proto"
"github.com/dubbogo/gost/log/logger"
)
func main() {
cli, err := client.NewClient(
client.WithClientURL("tri://127.0.0.1:20000"),
client.WithClientRetries(3),
)
if err != nil {
panic(err)
}
svc, err := greet.NewGreetService(cli)
if err != nil {
panic(err)
}
// request normal
resp, err := svc.Greet(context.Background(), &greet.GreetRequest{Name: "hello world"})
if err != nil {
logger.Error(err)
}
logger.Infof("Greet response: %s", resp.Greeting)
// request need retry
resp, err = svc.GreetRetry(context.Background(), &greet.GreetRequest{Name: "hello world"})
if err != nil {
logger.Error(err)
}
logger.Infof("Greet response: %s", resp.Greeting)
}
3.3案例效果先启动服务端，再启动客户端，访问GreetRetry时观察到服务端日志输出了重试次数。
2024-01-23 22:39:11 INFO logger/logging.go:22 [Not need retry, request success]
2024-01-23 22:39:11 INFO logger/logging.go:42 retry [1] times
2024-01-23 22:39:11 INFO logger/logging.go:42 retry [2] times
2024-01-23 22:39:11 INFO logger/logging.go:42 retry [3] times
2024-01-23 22:39:11 INFO logger/logging.go:42 retry success, current request time is [3]
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