Jobs and CronJobs
- Unlike other Kubernetes controllers, jobs manages a task up to its completion rather than to an open-ended desired state. In a way, the desired state of a job is its completion.
Video transcode task:
A non-parallel Job computing π to 2000 places
apiVersion: batch/v1
kind: Job
metadata:
name: pi
spec:
template:
spec:
container:
- name: pi
image: perl
command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"]
restartPolicy: Never
backoffLimit: 4
kubectl apply -f [JOB_FILE]
kubectl run pi --image perl --restart Never -- perl -Mbigum bpi -wle 'print bpi(2000)'
The role of a non-parallel Jobs
Parallel Jobs
The parallel job type creates multiple pods that work on the same task at the same time. Parallel job types are specified by setting the spec.parallelism value for a job greater than one.
- Fixed task completion count
- Processing a work queue
Parallel Job with fixed completion count
apiVersion: batch/v1
kind: Jobs
metadata:
name: my-app-job
spec:
completions: 3
parallelism: 2
template:
spec:
[...]
Parallel Job with a worker queue
apiVersion: batch/v1
kind: Jobs
metadata:
name: my-app-job
spec:
parallelism: 3
template:
spec:
[...]
Inspecting a Job
kubectl describe job [JOB_NAME]
kubectl get pod -l [job-name=my-app-job]
Scaling a Job
kubectl scale job [JOB_NAME] --replicas [VALUE]
Deleting a Job
kubectl delete -f [JOB_FILE]
kubectl delete job [JOB_NAME]
kubectl delete job [JOB_NAME] --cascade false
CronJob
Setting up a cron schedule under the CronJob spec
apvVersion: batch/v1
kind: CronJob
metadata:
name: my-app-job
spec:
schedule: "*/1 * * * *"
startingDeadlineSeconds: 3600
concurrencyPolicy: Forbid
suspend: True
successfulJobsHistoryLimit: 3
failedJobsHistoryLimit: 1
jobtemplate:
spec:
template:
spec:
[...]
CronJobs can be managed using kubectl
Create a CronJob
kubectl apply -f [FILE]
Inspect a CronJob
kubectl describe cronjob [NAME]
Delete a CronJob
kubectl delete cronjob [NAME]
