Kubernetes: manually restart a Cron Job

By | 07/27/2020
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We have a Kubernetes Cron Job which failed on its last run.

Let’s look for the root cause and then will see how to restart such a failed job.

List current jobs:

kk -n eks-prod-1-bttrm-apps-ns get cronjobs
NAME                                        SCHEDULE     SUSPEND   ACTIVE   LAST SCHEDULE   AGE
bttrm-apps-backend-reccuring-payment-cron   0 10 * * *   False     1        22m             45d

Check pods of the bttrm-apps-backend-reccuring-payment-cron Cron Job:

kk -n eks-prod-1-bttrm-apps-ns get pod | grep cron
bttrm-apps-backend-reccuring-payment-cron-1595757600-7n8rh   0/1     Completed          0          24h
bttrm-apps-backend-reccuring-payment-cron-1595844000-jzhrl   0/1     ImagePullBackOff   0          22m

The 1595844000-jzhrl pod was failed, check its logs:

kk -n eks-prod-1-bttrm-apps-ns describe pod bttrm-apps-backend-reccuring-payment-cron-1595844000-jzhrl
...
Normal   Pulling    21m (x4 over 23m)     kubelet, ip-10-4-55-187.us-east-2.compute.internal  Pulling image "projectname/projectname-apps:45.aa2416fb"
Warning  Failed     21m (x4 over 23m)     kubelet, ip-10-4-55-187.us-east-2.compute.internal  Failed to pull image "projectname/projectname-apps:45.aa2416fb": rpc error: code = Unknown desc = Error response from daemon: pull access denied for projectname/projectname-apps, repository does not exist or may require 'docker login'
Warning  Failed     21m (x4 over 23m)     kubelet, ip-10-4-55-187.us-east-2.compute.internal  Error: ErrImagePull
Warning  Failed     7m58s (x65 over 23m)  kubelet, ip-10-4-55-187.us-east-2.compute.internal  Error: ImagePullBackOff
...

Actually, here is the issue cause:

Failed to pull image … Error response from daemon: pull access denied

It wasn’t able to pull the image from a private repository because it has no  imagePullSecrets set:

kubectl explain CronJob.spec.jobTemplate.spec.template.spec.imagePullSecrets
KIND:     CronJob
VERSION:  batch/v1beta1
RESOURCE: imagePullSecrets <[]Object>
DESCRIPTION:
ImagePullSecrets is an optional list of references to secrets in the same
namespace to use for pulling any of the images used by this PodSpec. If
specified, these secrets will be passed to individual puller
implementations for them to use. For example, in the case of docker, only
DockerConfig type secrets are honored. More info:
https://kubernetes.io/docs/concepts/containers/images#specifying-imagepullsecrets-on-a-pod
LocalObjectReference contains enough information to let you locate the
referenced object inside the same namespace.

Edit the Cron Job:

kk -n eks-prod-1-bttrm-apps-ns edit cronjobs bttrm-apps-backend-reccuring-payment-cron

Add the Docker Hub authentification setting:

...
 imagePullSecrets: 
   - name: bttrm-docker-secret
...

And restart the Cron Job using the --from following by the Cron Job to be restarted, and then by a name for the new Cron Job – Kubernetes will create a new pod copied from your original Cron Job:

kk -n eks-prod-1-bttrm-apps-ns create job --from=cronjob/bttrm-apps-backend-reccuring-payment-cron reccuring-payment-cron-manual
job.batch/reccuring-payment-cron-manual created

Check pods:

kk -n eks-prod-1-bttrm-apps-ns create get pod
NAME                                                         READY   STATUS             RESTARTS   AGE
...
bttrm-apps-backend-reccuring-payment-cron-1595757600-7n8rh   0/1     Completed          0          24h
bttrm-apps-backend-reccuring-payment-cron-1595844000-jzhrl   0/1     ImagePullBackOff   0          32m
reccuring-payment-cron-manual-6lm62                          0/1     Completed          0          13s

cron-manual now is in the Completed status – we are done.


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