当库伯奈特准备就绪-探针返回假时会发生什么？要等多久？

Question

当Kubernetes readiness-probe返回false时会发生什么？在超时后库伯内特斯会重启那个吊舱吗？库伯奈特等了多久？

Answer 1

就绪探测不重新启动吊舱/容器，就绪探测确定容器已准备好为通信服务。如果容器被探测，并被认为没有“就绪”，容器将被从端点移除，并且在它再次准备就绪之前，流量不会发送到它。

1

2

3个kubectl explain pod.spec.containers.readinessProbe

KIND:     Pod
VERSION:  v1

RESOURCE: readinessProbe <Object>

DESCRIPTION:
     Periodic probe of container service readiness. Container will be removed
     from service endpoints if the probe fails. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

     Probe describes a health check to be performed against a container to
     determine whether it is alive or ready to receive traffic.

FIELDS:
   exec <Object>
     One and only one of the following should be specified. Exec specifies the
     action to take.

   failureThreshold <integer>
     Minimum consecutive failures for the probe to be considered failed after
     having succeeded. Defaults to 3. Minimum value is 1.

   httpGet  <Object>
     HTTPGet specifies the http request to perform.

   initialDelaySeconds  <integer>
     Number of seconds after the container has started before liveness probes
     are initiated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

   periodSeconds    <integer>
     How often (in seconds) to perform the probe. Default to 10 seconds. Minimum
     value is 1.

   successThreshold <integer>
     Minimum consecutive successes for the probe to be considered successful
     after having failed. Defaults to 1. Must be 1 for liveness and startup.
     Minimum value is 1.

   tcpSocket    <Object>
     TCPSocket specifies an action involving a TCP port. TCP hooks not yet
     supported

   timeoutSeconds   <integer>
     Number of seconds after which the probe times out. Defaults to 1 second.
     Minimum value is 1. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

让我们使用文档中的默认准备状态探针：

cat pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.2
    ports:
    - containerPort: 80
    readinessProbe:
      exec:
        command:
        - cat
        - /tmp/healthy
      initialDelaySeconds: 5
      periodSeconds: 5

要执行探测，kubelet在目标容器中执行cat /tmp/healthy命令。如果命令成功，则返回0，容器就就绪，可以“服务”。如果命令只返回0以外的任何内容，容器就不健康。

由于这个文件从一开始就不存在于容器中，所以当容器启动时，它将非常不健康。

date && k get pods nginx
Thu  2 Dec 2021 19:08:43 AST
NAME    READY   STATUS    RESTARTS   AGE
nginx   0/1     Running   0          66s

现在，让exec进入它并创建文件，这样命令就成功了。

k exec -it nginx -- bash
root@nginx:/# touch /tmp/healthy
root@nginx:/# exit
exit

再次检查：

date && k get pods nginx
Thu  2 Dec 2021 19:09:26 AST
NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          110s

再次移除：

k exec -it nginx -- bash
root@nginx:/# rm /tmp/healthy
root@nginx:/# exit
exit

检查：

date && k get pods nginx
Thu  2 Dec 2021 19:09:53 AST
NAME    READY   STATUS    RESTARTS   AGE
nginx   0/1     Running   0          2m17s