Configure request retries-Alibaba Cloud Service Mesh-阿里云帮助中心

ASM lets you define a retry policy for failed HTTP requests. You can specify the timeout for each retry, the number of retries, and the retry conditions. This topic describes how to configure request retries.

Preparations

Complete the required preparations and deploy the httpbin and sleep services. For more information, see Preparations.

Procedure

Verify that the service configuration is effective.

In the KubeConfig environment of your ACK cluster, run the following command to enter the sleep pod and start a bash session.
```
kubectl exec -it deploy/sleep -- sh
```

Run the following command to send a request to the httpbin service.

curl -I httpbin:8000/status/500

Expected output:

HTTP/1.1 500 Internal Server Error
server: envoy
date: Fri, 11 Aug 2023 10:03:06 GMT
content-type: text/html; charset=utf-8
access-control-allow-origin: *
access-control-allow-credentials: true
content-length: 0
x-envoy-upstream-service-time: 2

Use the following content to create a test scenario and configure a traffic rule for the httpbin application. Set the retry policy to five retries when a 5xx response is received. For more information, see Manage virtual services.

apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: httpbin-vs
  namespace: default
spec:
  hosts:
    - httpbin
  http:
    - retries:
        attempts: 5
        retryOn: 5xx
      route:
        - destination:
            host: httpbin

Verify that the configuration is effective.

In the KubeConfig environment of your ACK cluster, run the following command to enter the sleep pod and start a bash session.
```
kubectl exec -it deploy/sleep -- sh
```

Run the following command to send a request to the httpbin service and set the response status to 500.

curl -I httpbin:8000/status/500

Expected output:

HTTP/1.1 500 Internal Server Error
server: envoy
date: Fri, 11 Aug 2023 10:03:35 GMT
content-type: text/html; charset=utf-8
access-control-allow-origin: *
access-control-allow-credentials: true
content-length: 0
x-envoy-upstream-service-time: 382

Change the log level for the sleep service to view the logs of the retry process.
1. Run the following command to enter the sleep pod.
```
kubectl exec -it {sleep-pod-name} -- sh 
```
2. Run the following command to change the log level.
```
curl -XPOST http://localhost:15000/logging\?level\=debug
```

Run the following command to view the sleep logs.

kubectl logs {sleep-pod-name} -c istio-proxy |grep -i retry

Expected output:

2023-08-14T02:11:01.896684Z	debug	envoy router external/envoy/source/common/router/router.cc:1862	[C159776][S1686768772862290****] performing retry	thread=36
2023-08-14T02:11:01.932148Z	debug	envoy router external/envoy/source/common/router/router.cc:1862	[C159776][S1686768772862290****] performing retry	thread=36
2023-08-14T02:11:02.020689Z	debug	envoy router external/envoy/source/common/router/router.cc:1862	[C159776][S1686768772862290****] performing retry	thread=36
2023-08-14T02:11:02.170440Z	debug	envoy router external/envoy/source/common/router/router.cc:1862	[C159776][S1686768772862290****] performing retry	thread=36
2023-08-14T02:11:02.275478Z	debug	envoy router external/envoy/source/common/router/router.cc:1862	[C159776][S1686768772862290****] performing retry	thread=36