Kubernetes Job Guide: One-Time and Batch Workloads Made Easy

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# Kubernetes Job Guide: One-Time and Batch Workloads Made Easy

Kubernetes **Job** is a workload resource designed for **one-time or limited-run tasks**. Unlike Deployments, Jobs are not meant for always-on services — they **run until completion** and then exit.

In this guide, we’ll cover:

* What a Job is and why it exists
* Key features and real-world use cases
* How to configure retry policies and parallelism
* YAML examples for different scenarios
* Operational tips and best practices

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## Table of Contents

{% toc %}

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## 1. What Is a Kubernetes Job?

A Kubernetes Job manages **finite-duration tasks** by creating Pods that run to completion.
Once the task finishes successfully, the Job marks it as complete and stops creating new Pods.

**Examples:**

* Data migration scripts
* Database backups
* Generating reports
* Archiving logs
* Machine learning model training (single run)

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## 2. Why Use a Job Instead of a Pod?

Running a task in a Pod alone is possible but comes with limitations:

| Problem with Standalone Pod  | How Job Solves It             |
| ---------------------------- | ----------------------------- |
| Pod fails → manual restart   | Automatic retries             |
| No completion tracking       | Maintains success/fail status |
| Hard to manage multiple Pods | Supports parallel execution   |

Jobs provide **fault tolerance**, **state tracking**, and **parallel processing control** out-of-the-box.

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## 3. Key Features

| Feature          | Description                               |
| ---------------- | ----------------------------------------- |
| Completion-based | Stops once the task finishes successfully |
| Retry support    | Automatically restarts failed Pods        |
| State tracking   | Keeps history of successful/failed Pods   |
| Parallelism      | Run multiple Pods at the same time        |
| Resource control | Allocate CPU/memory per Job run           |

---

## 4. Job vs CronJob vs Deployment

| Resource   | Purpose                  | Execution Mode | End Condition |
| ---------- | ------------------------ | -------------- | ------------- |
| Job        | One-time/limited tasks   | Immediate run  | On completion |
| CronJob    | Scheduled recurring jobs | Based on cron  | On completion |
| Deployment | Always-on applications   | Continuous run | Manual stop   |

---

## 5. Basic YAML Example

```yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: data-processing-job
spec:
  template:
    spec:
      containers:
      - name: data-processor
        image: python:3.10
        command: ["python", "-c", "print('Processing data...')"]
      restartPolicy: OnFailure
  backoffLimit: 3

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kubectl apply -f job.yaml
kubectl get jobs
kubectl describe job data-processing-job
kubectl logs <pod-name>

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spec:
  backoffLimit: 5
  activeDeadlineSeconds: 300

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spec:
  parallelism: 5
  completions: 20