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Jobs & CronJobs

Key Takeaways for AI & Readers
  • Batch Processing: Kubernetes Jobs are designed for tasks that run to completion, rather than long-running services.
  • Job Configuration: Jobs ensure a specified number of Pods succeed, offering controls for completions, parallelism, and retry limits.
  • Scheduled Tasks: CronJobs automate the creation of Jobs on a recurring schedule, mimicking traditional cron functionality within the cluster.
  • Use Cases: Jobs are ideal for one-off tasks like migrations, while CronJobs suit routine operations like backups or reports.

While Deployments and StatefulSets are designed for long-running processes (services), Kubernetes also has first-class support for batch tasks.

1. Jobs​

A Job creates one or more Pods and ensures that a specified number of them successfully terminate. As pods successfully complete, the Job tracks the successful completions.

Use Cases​

  • One-off database migrations.
  • Batch processing (e.g., rendering a video frame).
  • System maintenance tasks.

Key Fields​

  • .spec.completions: How many pods need to succeed.
  • .spec.parallelism: How many pods can run at the same time.
  • .spec.backoffLimit: How many times to retry before marking the Job as failed.

2. CronJobs​

Schedule: */5 * * * *
Time: 0
Jobs are ephemeral. They run, complete, and then the Pod stops.

A CronJob creates a Job on a repeating schedule. It is essentially a crontab for your cluster.

Use Cases​

  • Daily database backups.
  • Sending digest emails.
  • Cleaning up old temporary files.

Schedule Syntax​

It uses standard Cron syntax: "*/1 * * * *" (Run every minute)