Run scheduled jobs reliably with CronJobs

Approach

Forbid overlapping runs, set a time zone and a starting deadline, keep history for debugging, bound retries and run time, and make the job idempotent.

Solution

apiVersion: batch/v1
kind: CronJob
metadata: {name: nightly-report}
spec:
  schedule: "0 2 * * *"
  timeZone: Europe/Berlin
  concurrencyPolicy: Forbid
  startingDeadlineSeconds: 600
  successfulJobsHistoryLimit: 3
  failedJobsHistoryLimit: 5
  jobTemplate:
    spec:
      backoffLimit: 2
      activeDeadlineSeconds: 3600
      ttlSecondsAfterFinished: 86400
      template:
        spec:
          restartPolicy: Never
          containers:
            - name: report
              image: ghcr.io/acme/report:2.1.0
              args: ["--date", "yesterday"]

Pitfalls

• Jobs that aren't idempotent: retries and rare double runs corrupt data.
• No alert when a CronJob stops succeeding (monitor last successful run time).

Variations

• Use a lock (database advisory lock) if even rare concurrent runs are unacceptable.
• Workflow engines (Argo Workflows) for multi-step pipelines.

Further reading: CronJob