12_Job.md

What is JOB?

A Job is a Kubernetes workload object used to run tasks that must complete successfully. Unlike Deployments or StatefulSets (which run continuously), a Job runs once , or a fixed number of times, until the task is completed.

Examples:

• Data processing task
• Backup operation
• Database migration
• File conversion
• Sending batch emails

A Job ensures that the task runs to completion even if Pod(s) fail.

Key Characteristics

1. Ensures task completion

A Job keeps creating Pods until the task succeeds:

• If a Pod fails → Job retries
• If a Pod completes → Job marks it done

It guarantees “at least once” execution.

2. Creates one or multiple Pods

Depending on configuration, a Job can run:

• 1 Pod once (default)
• Multiple pods in parallel (parallel processing)
• Pods sequentially (completions setting)

3. Retries on failure

If a Pod crashes:

• Job creates another Pod
• Job respects the backoffLimit (max retries)

4. Supports parallelism

Jobs allow parallel execution using:

• parallelism (how many Pods run at the same time)
• completions (how many total successful Pods needed)

parallelism: 5
completions: 20

• Run 5 Pods at a time until 20 finish.

5. Can run to completion and exit Once complete:

• The Job is marked Completed
• Pods remain for logs (unless TTL is set)

Use cases

• Batch processing
• ETL jobs