深入理解Istio流量管理的超时时间设置

环境准备

部署 httpbin 服务:

kubectl apply -f samples/httpbin/httpbin.yaml

部署 sleep 服务:

kubectl apply -f samples/sleep/sleep.yaml 

httpbin 服务作为接收请求的服务端, sleep 服务作为发送请求的客户端。

设置超时时间

sleep 服务中向 httpbin 服务的发出请求:

export SLEEP_POD=$(kubectl get pods -l app=sleep -o 'jsonpath={.items[0].metadata.name}')
kubectl exec "$SLEEP_POD" -c sleep -- time curl -o /dev/null -sS -w "%{http_code}\n" http://httpbin.org/delay/5

返回结果如下:

200
real    0m 5.69s
user    0m 0.00s
sys     0m 0.00s

可以看到,请求大约在 5 秒返回 200 (OK)。

创建虚拟服务,访问httpbin 服务时,请求超时设置为 3 秒:

kubectl apply -f - <apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: httpbin
spec:
  hosts:
  - httpbin
  http:
  - route:
    - destination:
        host: httpbin
    timeout: 3s
EOF

再此次访问,返回结果如下:

504
real    0m 3.01s
user    0m 0.00s
sys     0m 0.00s

可以看到,在 3 秒后出现了 504 (Gateway Timeout)。 Istio 在 3 秒后切断了响应时间为 5 秒的httpbin 服务的请求。接下来,我们深入地看一下,Istio是怎么切断请求的?

查看Envoy日志

执行一下命令,查看sleep 服务的Envoy日志:

kubectl logs -l app=sleep -c istio-proxy

可以看到sleep服务对httpbin服务的调用的日志:

{
     "authority": "httpbin:8000",
     "bytes_received": 0,
     "bytes_sent": 24,
     "connection_termination_details": null,
     "downstream_local_address": "172.24.146.239:8000",
     "downstream_remote_address": "172.24.158.25:40384",
     "duration": 3001,
     "method": "GET",
     "path": "/delay/5",
     "protocol": "HTTP/1.1",
     "request_id": "5ef38816-7f49-48c8-9627-2416e1716293",
     "requested_server_name": null,
     "response_code": 504,
     "response_code_details": "upstream_response_timeout",
     "response_flags": "UT",
     "route_name": null,
     "start_time": "2022-07-01T09:40:13.882Z",
     "upstream_cluster": "outbound|8000||httpbin.onemore.svc.cluster.local",
     "upstream_host": "172.24.158.96:80",
     "upstream_local_address": "172.24.158.25:32846",
     "upstream_service_time": null,
     "upstream_transport_failure_reason": null,
     "user_agent": "curl/7.81.0-DEV",
     "x_forwarded_for": null
}

其中,response_flagsUT,表示上游(upstream)请求超时,也就是sleep服务检测到了httpbin服务的请求超时。

执行一下命令,查看httpbin 服务的Envoy日志:

kubectl logs -l app=httpbin -c istio-proxy

可以看到httpbin服务被sleep服务调用的Envoy日志:

{
     "authority": "httpbin:8000",
     "bytes_received": 0,
     "bytes_sent": 0,
     "connection_termination_details": null,
     "downstream_local_address": "172.24.158.96:80",
     "downstream_remote_address": "172.24.158.25:32846",
     "duration": 2997,
     "method": "GET",
     "path": "/delay/5",
     "protocol": "HTTP/1.1",
     "request_id": "5ef38816-7f49-48c8-9627-2416e1716293",
     "requested_server_name": "outbound_.8000_._.httpbin.onemore.svc.cluster.local",
     "response_code": 0,
     "response_code_details": "downstream_remote_disconnect",
     "response_flags": "DC",
     "route_name": "default",
     "start_time": "2022-07-01T09:40:13.885Z",
     "upstream_cluster": "inbound|80||",
     "upstream_host": "172.24.158.96:80",
     "upstream_local_address": "127.0.0.6:35701",
     "upstream_service_time": null,
     "upstream_transport_failure_reason": null,
     "user_agent": "curl/7.81.0-DEV",
     "x_forwarded_for": null
}

其中,response_flagsDC,表示下游(downstream)连接中断,也就是sleep服务的调用请求被中断了。

深入分析

通过Envoy日志,我们可以做出一些分析和判断:

httpbin服务的请求正常的时候,调用过程如下图:

深入理解Istio流量管理的超时时间设置_第1张图片

httpbin服务的请求超时的时候,调用过程如下图:

深入理解Istio流量管理的超时时间设置_第2张图片

虽然,我们在httpbin服务上设置的请求超时时间,但实际上主动断开请求的却是sleep服务的Envoy。

清理

kubectl delete virtualservice httpbin
kubectl delete -f samples/httpbin/httpbin.yaml
kubectl delete -f samples/sleep/sleep.yaml 

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