CronJob

CronJob is a Kubernetes resource that runs Jobs on a repeating schedule. It uses a cron-like schedule to trigger the creation of Job objects at specified times.

The CronJob consists of a schedule and a jobTemplate that defines the Job to be created. When the schedule time arrives, the CronJob controller creates a Kubernetes Job resource from the template and starts the pods. The controller enforces the concurrencyPolicy, which can be Allow, Forbid, or Replace.

Other important fields include startingDeadlineSeconds, which allows skipping late schedules, and suspend, which can pause scheduling. In newer versions, CronJob supports timeZone to specify the time zone for the schedule. The CronJob controller can retain a limited number of completed or failed Jobs via successfulJobHistoryLimit and failedJobHistoryLimit.

Scheduling details: The schedule uses Cron syntax with five fields (minute, hour, day of month, month, day of week). Jobs created by a CronJob run to completion, launching pods that perform the work. Each Job follows the standard Job lifecycle and is independent of other Jobs unless constrained by concurrencyPolicy.

Use cases and considerations: common tasks include periodic data processing, backups, report generation, and cleanup. To ensure reliability, write idempotent containers, set resource requests and limits, monitor Job status, and configure history limits to control resource use.