What is a Job?
- Docker & Kubernetes course
- Advanced
- Lesson 25/70
- 4 min
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
3.1415926535897932384626433832795028841971693993751Watching 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 gocPractice 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.
Starter code
# buraya yazSample solution
kubectl create job selam --image=busybox:1.36 -- echo merhaba
kubectl wait --for=condition=complete job/selam --timeout=60s
kubectl logs job/selamExpected output
job.batch/selam created job.batch/selam condition met merhaba
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 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 Correct answer
Explanation: A Deployment is for continuously running processes.
2 Wait until the Job completes.
kubectl wait --for=condition=____ job/goc --timeout=120skubectl wait --for=condition=complete job/goc --timeout=120sExplanation: A Job's success condition is Complete.
3 Match.
| Term | Meaning |
|---|---|
Job |
Run to completion |
Deployment |
Run continuously |
COMPLETIONS 1/1 |
Finished successfully |
kubectl wait |
Wait for a condition |