Init container not restarting on pod restart-CodePudding

I have an init container that do some stuff that needs for the main container to run correctly, like creating some directories and a liveness probe that may fail if one of these directories were deleted. When the pod is restarted due to fail of liveness probe I expect that init container is also being restarted, but it won't.

This is what kubernetes documentation says about this:

If the Pod restarts, or is restarted, all init containers must execute again. https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

Easiest way to prove this behavior was to use the example of the pod from k8s documentation, add a liveness probe that always fails and expect that init container to be restarted, but again, it is not behaving as expected.

This is the example I'm working with:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  restartPolicy: Always
  containers:
  - name: myapp-container
    image: busybox:1.28
    command: ['sh', '-c', 'echo "App started at $(date)" && tail -f /dev/null']
    livenessProbe:
      exec:
        command:
        - sh
        - -c
        - exit 1
      initialDelaySeconds: 1
      periodSeconds: 1
  initContainers:
  - name: myapp-init
    image: busybox:1.28
    command: ['/bin/sh', '-c', 'sleep 5 && echo "Init container started at $(date)"']

Sleep and date command are there to confirm that init container was restarted.

The pod is being restarted:

NAME            READY   STATUS    RESTARTS   AGE
pod/myapp-pod   1/1     Running   4          2m57s

But from logs it's clear that init container don't:

$ k logs pod/myapp-pod myapp-init
Init container started at Thu Jun 16 12:12:03 UTC 2022

$ k logs pod/myapp-pod  myapp-container
App started at Thu Jun 16 12:14:20 UTC 2022

I checked it on both v1.19.5 and v1.24.0 kubernetes servers.

The question is how to force the init container to restart on pod restart.

CodePudding user response：

The restart number refers to container restarts, not pod restarts.

init container need to run only once in a pos lifetime, and you need to design your containers like that, you can read this PR, and especially this comment