Cronjob of existing Pod - openshift

Question

I have a django app running on Openshift 3. I need to run certain manage.py commands on a regular basis. In Openshift 2 I used the Cron gear and now in Openshift 3 I want to use the CronJob pod type.
I want to create a pod for the cronjob, use the same source as the django app is using, but not expose it.
For example:
W1 - Django app
D1 - Postgres DB
M1 - django app for manage.py jobs, run as a cronjob pod.
Any help is appreciated.

Answer 1

You want to use a scheduled job.
https://docs.openshift.com/container-platform/3.5/dev_guide/cron_jobs.html
https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/
https://blog.openshift.com/openshift-jobs/
Note that at this time (OpenShift 3.5), you have to use batch/v2alpha1 as the API version. Be careful of out of date documentation showing older version labels.
What I am not sure of is how you can easily reference the image associated with an existing imagestream produced when you used the S2I builder to build you application and you want to use the same image. The base Kubernetes object for this expects you to refer to the image from the image registry. You would thus need to work that out by looking at the imagestream and copying the image registry IP and image details over by hand.
UPDATE 1
See:
https://stackoverflow.com/a/45227960/128141
for details of how from OpenShift 3.6 you can have it resolve the imagestream name automatically. That mechanism is still alpha status in 3.6, but does work.

Answer 2

I've gotten it to work with specifying the image name in the YAML, but then tried to get it to work as part of the template, but ran into an error when trying to use the batch/v1 version on this server
Cannot create cron job "djangomanage". The API version batch/v1 for kind CronJob is not supported by this server.
My template code is
- apiVersion: batch/v1
kind: CronJob
metadata:
name: djangomanage
spec:
schedule: "*/5 * * * *"
jobTemplate:
spec:
template:
spec:
containers:
- name: djangomanage
image: '${NAME}:latest'
env:
- name: APP_SCRIPT
value: "/opt/app-root/src/cron.sh"
restartPolicy: Never
CRON.SH
python /opt/app-root/src/manage.py

Answer 3

you need to update line 1 with this:
- apiVersion: batch/v1beta1
see link below:
https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.18/#cronjob-v1beta1-batch