How to Run Batch Workloads with Jobs and CronJobs

Jobs run tasks to completion, while CronJobs schedule recurring jobs. Use them for batch processing, data pipelines, backups, and maintenance tasks.

Basic Job

# simple-job.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: data-import
spec:
  template:
    spec:
      containers:
        - name: import
          image: data-processor:v1
          command: ["python", "import.py"]
          env:
            - name: SOURCE_URL
              value: "https://data.example.com/dataset.csv"
      restartPolicy: Never  # Required for Jobs
  backoffLimit: 4  # Retry up to 4 times on failure

# Create and monitor job
kubectl apply -f simple-job.yaml
kubectl get jobs
kubectl describe job data-import

# View job logs
kubectl logs job/data-import

# Delete completed job
kubectl delete job data-import

Job with Parallelism

# parallel-job.yaml
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 unique index
  template:
    spec:
      containers:
        - name: processor
          image: processor:v1
          command: ["process-chunk"]
          env:
            - name: JOB_INDEX
              valueFrom:
                fieldRef:
                  fieldPath: metadata.annotations['batch.kubernetes.io/job-completion-index']
      restartPolicy: Never

Job with Deadline

# deadline-job.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: time-sensitive-job
spec:
  activeDeadlineSeconds: 600  # Kill after 10 minutes
  backoffLimit: 3
  template:
    spec:
      containers:
        - name: worker
          image: worker:v1
          resources:
            limits:
              cpu: "2"
              memory: "4Gi"
      restartPolicy: Never

Job TTL (Auto-Cleanup)

# ttl-job.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: cleanup-job
spec:
  ttlSecondsAfterFinished: 3600  # Delete 1 hour after completion
  template:
    spec:
      containers:
        - name: cleanup
          image: cleanup:v1
      restartPolicy: Never

Basic CronJob

# cronjob.yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: daily-backup
spec:
  schedule: "0 2 * * *"  # 2 AM daily
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: backup
              image: backup-tool:v1
              command: ["backup.sh"]
              env:
                - name: BACKUP_DESTINATION
                  value: "s3://backups/daily"
          restartPolicy: OnFailure

Cron Schedule Syntax

flowchart LR
    subgraph Cron["Cron Schedule Format: * * * * *"]
        M["minute<br/>(0-59)"] ~~~ H["hour<br/>(0-23)"] ~~~ DOM["day of month<br/>(1-31)"] ~~~ MO["month<br/>(1-12)"] ~~~ DOW["day of week<br/>(0-6)"]
    end

# Cron format: minute hour day-of-month month day-of-week

# Examples:
schedule: "*/15 * * * *"     # Every 15 minutes
schedule: "0 * * * *"        # Every hour
schedule: "0 0 * * *"        # Daily at midnight
schedule: "0 2 * * 0"        # Weekly on Sunday at 2 AM
schedule: "0 0 1 * *"        # Monthly on 1st at midnight
schedule: "30 4 * * 1-5"     # Weekdays at 4:30 AM

CronJob Concurrency Policy

# concurrency-cronjob.yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: report-generator
spec:
  schedule: "0 */6 * * *"  # Every 6 hours
  concurrencyPolicy: Forbid  # Don't start new if previous running
  # Options:
  # - Allow: Default, concurrent jobs allowed
  # - Forbid: Skip if previous job still running
  # - Replace: Cancel running job, start new one
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: report
              image: reporter:v1
          restartPolicy: OnFailure

CronJob History Limits

# history-cronjob.yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: cleanup-task
spec:
  schedule: "0 3 * * *"
  successfulJobsHistoryLimit: 3   # Keep last 3 successful jobs
  failedJobsHistoryLimit: 1       # Keep last 1 failed job
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: cleanup
              image: cleanup:v1
          restartPolicy: OnFailure

Suspend CronJob

# suspended-cronjob.yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: maintenance
spec:
  schedule: "0 4 * * *"
  suspend: true  # Paused - won't create new jobs
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: maintenance
              image: maintenance:v1
          restartPolicy: OnFailure

# Toggle suspend
kubectl patch cronjob maintenance -p '{"spec":{"suspend":true}}'
kubectl patch cronjob maintenance -p '{"spec":{"suspend":false}}'

Starting Deadline

# deadline-cronjob.yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: time-critical
spec:
  schedule: "0 * * * *"
  startingDeadlineSeconds: 300  # Must start within 5 min of schedule
  # If missed by more than 300s, skip this run
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: task
              image: task:v1
          restartPolicy: OnFailure

Job with Init Container

# job-with-init.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: data-pipeline
spec:
  template:
    spec:
      initContainers:
        - name: download-data
          image: curlimages/curl
          command: ["curl", "-o", "/data/input.csv", "https://data.example.com/data.csv"]
          volumeMounts:
            - name: data
              mountPath: /data
      containers:
        - name: process
          image: processor:v1
          command: ["python", "process.py", "/data/input.csv"]
          volumeMounts:
            - name: data
              mountPath: /data
      volumes:
        - name: data
          emptyDir: {}
      restartPolicy: Never

Monitor Jobs

# List jobs
kubectl get jobs
kubectl get jobs -w  # Watch

# List cronjobs
kubectl get cronjobs

# View job pods
kubectl get pods -l job-name=data-import

# Job status
kubectl describe job data-import

# View recent executions
kubectl get jobs --selector=job-name=daily-backup

# Manually trigger cronjob
kubectl create job --from=cronjob/daily-backup manual-backup

Job Patterns

# Work Queue Pattern
apiVersion: batch/v1
kind: Job
metadata:
  name: queue-worker
spec:
  parallelism: 5
  completions: 5
  template:
    spec:
      containers:
        - name: worker
          image: queue-worker:v1
          env:
            - name: QUEUE_URL
              value: "redis://queue:6379"
      restartPolicy: OnFailure
---
# Single Leader Pattern
apiVersion: batch/v1
kind: Job
metadata:
  name: coordinator
spec:
  completions: 1
  parallelism: 1
  template:
    spec:
      containers:
        - name: leader
          image: coordinator:v1
      restartPolicy: Never

Cleanup Old Jobs

# Delete completed jobs older than 1 hour
kubectl delete jobs --field-selector status.successful=1 \
  --all-namespaces

# Delete failed jobs
kubectl delete jobs --field-selector status.failed=1

# Delete all jobs in namespace
kubectl delete jobs --all -n batch-jobs

Summary

Jobs run tasks to completion with configurable parallelism and retry policies. Use completions for total tasks and parallelism for concurrent pods. Set activeDeadlineSeconds for timeouts and ttlSecondsAfterFinished for auto-cleanup. CronJobs schedule recurring jobs using cron syntax. Control concurrency with concurrencyPolicy (Allow/Forbid/Replace). Use startingDeadlineSeconds for time-sensitive jobs. Manually trigger CronJobs with kubectl create job --from=cronjob/name.

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