CronJob for Scheduled Batch Processing

Kubernetes CronJobs

CronJobs create Jobs on a schedule, similar to cron on Linux. They are ideal for periodic tasks like database maintenance, report generation, cache warming, and data synchronization.

Key Configuration

apiVersion: batch/v1
kind: CronJob
metadata:
  name: db-cleanup
  labels:
    app: "db-cleanup"
spec:
  schedule: "0 2 * * *"
  concurrencyPolicy: Forbid
  successfulJobsHistoryLimit: 3
  failedJobsHistoryLimit: 1
  jobTemplate:
    spec:
      template:
        spec:
          restartPolicy: OnFailure
          containers:
            - name: cleanup
              image: my-cleanup-script:latest
              env:
                - name: DATABASE_URL
                  value: "postgres://admin:changeme@postgres:5432/mydb"
              resources:
                requests:
                  cpu: "100m"
                  memory: "128Mi"
                limits:
                  cpu: "500m"
                  memory: "256Mi"

Schedule Syntax

The schedule field uses standard cron syntax with 5 fields:

Field	Values	Example
Minute	0-59	0 (at minute 0)
Hour	0-23	2 (at 2 AM)
Day of month	1-31	* (every day)
Month	1-12	* (every month)
Day of week	0-6	* (every day)

Common schedules:

• 0 2 * * * — Daily at 2 AM
• */15 * * * * — Every 15 minutes
• 0 0 * * 0 — Weekly on Sunday at midnight
• 0 0 1 * * — Monthly on the 1st at midnight

Concurrency Policy

• Allow (default): Multiple jobs can run simultaneously
• Forbid: Skip the new job if the previous one is still running
• Replace: Cancel the running job and start a new one

For database cleanup, Forbid prevents overlapping cleanup operations that could cause locks or conflicts.

Restart Policy

CronJob pods must use restartPolicy: OnFailure or restartPolicy: Never. The default Always policy is not allowed because completed jobs should not restart indefinitely.