Kubernetes Jobs and CronJobs Guide

💡 Quick Answer: deployments

The Problem

This is one of the most searched Kubernetes topics with thousands of monthly searches. A comprehensive, production-ready guide prevents hours of trial and error.

The Solution

Create a Job

apiVersion: batch/v1
kind: Job
metadata:
  name: data-migration
spec:
  backoffLimit: 3            # Retry 3 times on failure
  activeDeadlineSeconds: 600 # Timeout after 10 minutes
  ttlSecondsAfterFinished: 3600  # Auto-cleanup after 1 hour
  template:
    spec:
      restartPolicy: Never   # Required: Never or OnFailure
      containers:
        - name: migrate
          image: my-app:v1
          command: ["python", "migrate.py"]
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: db-creds
                  key: url

Parallel Jobs

apiVersion: batch/v1
kind: Job
metadata:
  name: batch-processor
spec:
  completions: 10          # Total tasks to complete
  parallelism: 3           # Run 3 pods at a time
  completionMode: Indexed  # Each pod gets JOB_COMPLETION_INDEX (0-9)
  template:
    spec:
      restartPolicy: Never
      containers:
        - name: worker
          image: batch-worker:v1
          command: ["process", "--partition=$(JOB_COMPLETION_INDEX)"]

CronJob

apiVersion: batch/v1
kind: CronJob
metadata:
  name: nightly-backup
spec:
  schedule: "0 2 * * *"           # 2 AM daily
  timeZone: "Europe/Rome"         # K8s 1.27+
  concurrencyPolicy: Forbid       # Don't overlap runs
  successfulJobsHistoryLimit: 3   # Keep last 3 successful
  failedJobsHistoryLimit: 3       # Keep last 3 failed
  startingDeadlineSeconds: 300    # Skip if >5min late
  jobTemplate:
    spec:
      backoffLimit: 2
      template:
        spec:
          restartPolicy: OnFailure
          containers:
            - name: backup
              image: backup-tool:v1
              command: ["backup.sh"]

Cron Schedule Reference

# Manual trigger
kubectl create job manual-backup --from=cronjob/nightly-backup

# Check status
kubectl get jobs
kubectl get cronjobs
kubectl describe job data-migration

graph TD
    A[CronJob: nightly-backup] -->|2 AM daily| B[Creates Job]
    B --> C[Pod runs backup.sh]
    C -->|Success| D[Job completed]
    C -->|Failure| E{Retry?}
    E -->|backoffLimit not reached| F[New pod]
    E -->|backoffLimit reached| G[Job failed]

Frequently Asked Questions

Job restartPolicy: Never vs OnFailure?

Never: failed pods stay (for log inspection), new pods created for retries. OnFailure: same pod restarts in-place. Use Never for debugging, OnFailure for production.

What if a CronJob takes longer than the interval?

concurrencyPolicy: Forbid skips the new run. Replace kills the running job and starts new. Allow (default) runs both concurrently — usually not what you want.

Best Practices

• Start with the simplest configuration that solves your problem
• Test in staging before production
• Use kubectl describe and events for troubleshooting
• Document team conventions for consistency

Key Takeaways

• This is fundamental Kubernetes operational knowledge
• Follow established conventions and recommended labels
• Monitor and iterate based on real production behavior
• Automate repetitive tasks to reduce human error