Kubernetes: Is it possible to mount volumes to a container running as a CronJob?

Question

I'm attempting to create a Kubernetes CronJob to run an application every minute.

A prerequisite is that I need to get my application code onto the container that runs within the CronJob. I figure that the best way to do so is to use a persistent volume, a pvclaim, and then defining the volume and mounting it to the container. I've done this successfully with containers running within a Pod, but it appears to be impossible within a CronJob? Here's my attempted configuration:

apiVersion: batch/v2alpha1 kind: CronJob metadata:   name: update_db spec:   volumes:   - name: application-code     persistentVolumeClaim:       claimName: application-code-pv-claim   schedule: "*/1 * * * *"   jobTemplate:     spec:       template:         spec:           containers:           - name: update-fingerprints             image: python:3.6.2-slim             command: ["/bin/bash"]             args: ["-c", "python /client/test.py"]           restartPolicy: OnFailure 

The corresponding error:

error: error validating "cron-applications.yaml": error validating data: found invalid field volumes for v2alpha1.CronJobSpec; if you choose to ignore these errors, turn validation off with --validate=false

I can't find any resources that show that this is possible. So, if not possible, how does one solve the problem of getting application code into a running CronJob?

Answer 1

A CronJob uses a PodTemplate as everything else based on Pods and can use Volumes. You placed your Volume specification directly in the CronJobSpec instead of the PodSpec, use it like this:

apiVersion: batch/v1beta1 kind: CronJob metadata:   name: update-db spec:   schedule: "*/1 * * * *"   jobTemplate:     spec:       template:         spec:           containers:           - name: update-fingerprints             image: python:3.6.2-slim             command: ["/bin/bash"]             args: ["-c", "python /client/test.py"]             volumeMounts:             - name: application-code               mountPath: /where/ever           restartPolicy: OnFailure           volumes:           - name: application-code             persistentVolumeClaim:               claimName: application-code-pv-claim 

Answer 2

For the other question in there: "how does one solve the problem of getting application code into a running CronJob?"

You build your own image that contains the code. This is how it is normally done.

FROM python:3.6.2-slim ADD test.py /client/test.py  CMD ['python','-c','/client/test.py'] 

Build and push to the docker registry.

docker build -t myorg/updatefingerprints docker push myorg/updatefingerprints 

Use this image in the descriptor.

apiVersion: batch/v2alpha1 kind: CronJob metadata:   name: update_db spec:   volumes:   - name: application-code     persistentVolumeClaim:       claimName: application-code-pv-claim   schedule: "*/1 * * * *"   jobTemplate:     spec:       template:         spec:           containers:           - name: update-fingerprints             image: myorg/update-fingerprints             imagePullPolicy: Always           restartPolicy: OnFailure 

This requires thinking quite differently about configuration management and version control.