k8s CronJob loop on list of pods - bash

Question

I want to run a loop on the pods in specific namespace, however the trick is to do it in a cronJob,is it possible inline?
kubectl get pods -n foo
The trick here is after you get the list of the pods, I need to loop on then and delete each one by one with timeout of 15 seconde, is it possible to do it in cronJob?
apiVersion: batch/v1
kind: CronJob
metadata:
name: restart
namespace: foo
spec:
concurrencyPolicy: Forbid
schedule: "*/1 * * * *"
jobTemplate:
spec:
backoffLimit: 2
activeDeadlineSeconds: 600
template:
spec:
serviceAccountName: pod-exterminator
restartPolicy: Never
containers:
- name: kubectl
image: bitnami/kubectl:1.22.3
command:
- 'kubectl'
- 'get'
- 'pods'
- '--namespace=foo'
When running the above script it works, but when you want to run loop its get complicated, how can I do it inline?

Answer 1

In your case you can use something like this:
apiVersion: batch/v1
kind: CronJob
metadata:
name: restart
namespace: foo
spec:
concurrencyPolicy: Forbid
schedule: "*/1 * * * *"
jobTemplate:
spec:
backoffLimit: 2
activeDeadlineSeconds: 600
template:
spec:
serviceAccountName: pod-exterminator
restartPolicy: Never
containers:
- name: kubectl
image: bitnami/kubectl:1.22.3
command:
- /bin/sh
- -c
- kubectl get pods -o name | while read -r POD; do kubectl delete "$POD"; sleep 15; done
However, do you really need to wait 15 seconds? If you want to be sure that pod is gone before deleting next one, you can use --wait=true, so the command will become:
kubectl get pods -o name | while read -r POD; do kubectl delete "$POD" --wait; done

Answer 2

Here is something similar I did to cleanup rabbitmq instances once our helm chart was deleted (hyperkube image can run kubectl commands):
apiVersion: batch/v1
kind: Job
metadata:
name: {{ template "rabbitmq-cluster-operator.fullname" . }}-delete-instances
namespace: {{ .Release.Namespace }}
annotations:
"helm.sh/hook": pre-delete
"helm.sh/hook-weight": "1"
"helm.sh/hook-delete-policy": before-hook-creation,hook-succeeded,hook-failed
labels:
app: {{ template "rabbitmq-cluster-operator.name" . }}
release: {{ .Release.Name }}
spec:
template:
metadata:
name: {{ template "rabbitmq-cluster-operator.fullname" . }}-delete- instances
labels:
app: {{ template "rabbitmq-cluster-operator.name" . }}
annotations:
sidecar.istio.io/inject: "false"
spec:
restartPolicy: Never
serviceAccountName: {{ template "rabbitmq-cluster-operator.serviceAccountName" . }}
containers:
- name: kubectl
image: "{{ .Values.global.hyperkube.image.repository }}/{{
.Values.global.hyperkube.image.name }}:{{ .Values.global.hyperkube.image.tag }}"
imagePullPolicy: "{{ .Values.global.hyperkube.image.pullPolicy }}"
command:
- /bin/sh
- -c
- >
kubectl get rabbitmqclusters | while read -r entry; do
name=$(echo $entry | awk '{print $1}');
kubectl delete rabbitmqcluster $name -n {{ .Release.Namespace }};
done
Note this is a job but something similar can be done in a cronjob.