What is a Job?

Learn that a Job runs tasks to completion.

What is a Job?

A Job produces pods that run a task to the end and finish successfully: database migration, batch data processing, generating reports. Unlike a Deployment, a pod isn't restarted when it finishes and the Job is marked "complete". If a pod fails, the Job retries it.

$ kubectl create job pi --image=perl:5.40 -- perl -Mbignum=bpi -wle "print bpi(50)"
$ kubectl get jobs
NAME   STATUS     COMPLETIONS   DURATION   AGE
pi     Complete   1/1           8s         20s
$ kubectl logs job/pi
3.1415926535897932384626433832795028841971693993751

Watching a Job

To wait for a Job to finish, kubectl wait is used; in CI pipelines it prevents deploying the application before the migration is done. Finished Jobs and their pods stay; ttlSecondsAfterFinished deletes them automatically after a given time:

kubectl wait --for=condition=complete job/goc --timeout=120s
kubectl logs job/goc
kubectl delete job goc

Exercise A one-off task

Write three commands: create a Job named selam with the busybox:1.36 image running the echo merhaba command; wait for the Job to complete with a 60-second timeout; show the Job's logs.

Show example solution

kubectl create job selam --image=busybox:1.36 -- echo merhaba
kubectl wait --for=condition=complete job/selam --timeout=60s
kubectl logs job/selam

Test yourself

Why run a database migration as a Job instead of a Deployment?
- A Job is faster
- A Deployment can't connect to a database
- A Job is free
- The migration must run once and finish; a Deployment restarts a finished pod
Show answer

The migration must run once and finish; a Deployment restarts a finished pod — A Deployment is for continuously running processes.

Wait until the Job completes.

kubectl wait --for=condition=____ job/goc --timeout=120s

Show answer

kubectl wait --for=condition=complete job/goc --timeout=120s

Match.

Job

Run to completion
Deployment

Run continuously
COMPLETIONS 1/1

Finished successfully
kubectl wait

Wait for a condition

Next lesson: Job YAML

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