Cron jobs is one of my favorite feature in Kubernetes. I use them for backups, data retention, clean ups and some monitoring as well.

Cron Jobs feature is still in alpha. It is not enabled by default in Kubernetes 1.6 (and possible in 1.7 as well).

If you have Kubernetes setup by kubeadm, just find the file

/etc/kubernetes/manifests/kube-apiserver.yaml

Add a command argument to this Pod definition

--runtime-config=batch/v2alpha1=true

After that restart kubelet.service (if on ubuntu)

sudo systemctl restart kubelet.service

Few caveats about Cron Jobs:

• Cron Jobs create Jobs. Jobs are running till successful completion. If your container constantly fails you will end up with a lot of failed containers. This is a proposal for this issue: Backoff policy and failed pod limit. While I was working on my cron jobs I ended up few times in this situation. To deal with that - delete the job and after that clean all pods created by that job

kubectl delete pod -l job-name=<job_name>

• Dashboard does not support Cron Jobs, so you will not see them. But you will see the Jobs created by Cron Jobs.

• Think about concurrencyPolicy which you want to apply. Default is Allow. Most of Cron Jobs I created have Forbid.

• Set successfulJobsHistoryLimit and failedJobsHistoryLimit. These values are unset by default. I usually use successfulJobsHistoryLimit: 1 and failedJobsHistoryLimit: 3.

See Also

• Kubernetes network
• Using kubeadm to Create a Kubernetes on Ubuntu server