cron-operator/README.md

Cron operator for Kubernetes

Manages multiple CronJobs with same image, but different commands and workdirs. Supports mounting of persistent volume to save results somewhere, ENV variables configmaps, concurrency and restart policy.

Build sources

• You definitly need a Golang installed (easy install for Ubuntu)
• Clone repository https://git.blindage.org/21h/cron-operator.git to your computer
• Open Makefile and change images registry to yours, then run make && make push
  Or run docker build -t cron-operator . to make image and push to your repo later
• Upload image to your registry

Prebuilt images

You can find images here https://hub.docker.com/r/iam21h/cron-operator. Pin version number in operator.yaml if you do not want automaticaly get new features and bugs.

Deploy operator

Cluster scoped installation:

kubectl -f deploy/crds/blindage_v1alpha1_cronop_crd.yaml
kubectl -f deploy/clusterrole.yaml
kubectl -f deploy/clusterrole_binding.yaml # service account namespace here
kubectl -n default -f deploy/service_account.yaml
kubectl -n default -f deploy/operator.yaml

Change operator.yaml if you want operator watch only specified namespace. Check deploy directory, may be you want to use Role instead of ClusterRole.

Settings

In your CronOp resource you can set image, parameters and tasks. CronJobs is a result of reconciling tasks section, some parameters can be global and overrided in each task. Remember, CronJob, Pod and Job is a different things.

This parameters can be set in global section or each task:

• Set Configmap with ENV variables
  envConfigmap: default empty

• How to restart Pod
  restartPolicy: OnFailure | Never | Always

• Limit Job restarts
  backoffLimit: 0 | integer

• Allow Cronjob to run concurrent Jobs
  concurrencyPolicy: Allow | Forbid | Replace

• Set standard kubernetes Pod security context podSecurityContext: default empty

Global history limits:

• successfulJobsHistoryLimit: 3 | integer
• failedJobsHistoryLimit: 3 | integer

Also you can save intermediate results in mounted persistent volume. You can set PVC name with PersistentVolumeName, mount point with PersistentVolumePath and PersistentVolumeSubPath. It’s easy.

Global affinity, node selection and tolerations, have standard kubernetes specs:

• nodeSelector: default empty
• affinity: default empty
• tolerations: default empty

Global resource limiting also kubernetes standard, but separated:

• podRequests: default empty
• podLimits: default empty

Look into pkg/apis/blindage/v1alpha1/cronop_types.go for your CustomResource syntax.

Your first CronOp deployment

Good sample you can find in deploy/test-cron.yaml, see it in case of questions.

This resource can help you run your first tasks:

---
apiVersion: blindage.org/v1alpha1
kind: CronOp
metadata:
  name: mycron
spec:
  image: "python:3"
  tasks:
  - name: print-test
    commands: ['python','-c', 'print("doing nothing")']
    schedule: "* * * * *"

If you delete this resource operator will delete CronJobs and Jobs.

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Copyright by Vladimir Smagin (21h) 2019
http://blindage.org email: 21h@blindage.org
Project page: https://git.blindage.org/21h/cron-operator