Jobs and CronJobs¶

Jobs

A Job creates one or more Pods and ensures that a specified number of them successfully terminate. As pods successfully complete, the Job tracks the successful completions. When a specified number of successful completions is reached, the task (ie, Job) is complete. Deleting a Job will clean up the Pods it created.

CronJobs

One CronJob object is like one line of a crontab (cron table) file. It runs a job periodically on a given schedule, written in Cron format.

CronJob schedules use the time zone of the kube-controller-manager, which is usually UTC. Set spec.timeZone (for example America/Chicago) to schedule in a specific time zone. Use successfulJobsHistoryLimit and failedJobsHistoryLimit to control how many finished Jobs are kept, and concurrencyPolicy to decide whether runs may overlap.

Resources¶

OpenShiftKubernetes

Automated Tasks with Cron

References¶

It computes π to 2000 places and prints it out

apiVersion: batch/v1
kind: Job
metadata:
  name: pi
spec:
  template:
    spec:
      containers:
        - name: pi
          image: perl
          command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never
  backoffLimit: 4

Running in parallel

apiVersion: batch/v1
kind: Job
metadata:
  name: pi
spec:
  parallelism: 2
  completions: 3
  template:
    spec:
      containers:
        - name: pi
          image: perl
          command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never
  backoffLimit: 4

apiVersion: batch/v1
kind: CronJob
metadata:
  name: hello
spec:
  schedule: "*/1 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: hello
              image: busybox
              args:
                - /bin/sh
                - -c
                - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure

OpenShiftKubernetes

Gets Jobs

oc get jobs

Gets Job Description

oc describe job pi

Gets Pods and logs from the Job

oc get pods -l job-name=pi
oc logs job/pi

Deletes Job

oc delete job pi

Gets CronJob

oc get cronjobs

Describes CronJob

oc describe cronjob hello

Runs the CronJob now, without waiting for the schedule

oc create job hello-now --from=cronjob/hello
oc logs job/hello-now

Deletes CronJob

oc delete cronjob hello