Azure Red Hat OpenShift 3.11 will be retired 30 June 2022. Support for creation of new Azure Red Hat OpenShift 3.11 clusters continues through 30 November 2020. Following retirement, remaining Azure Red Hat OpenShift 3.11 clusters will be shut down to prevent security vulnerabilities.
Follow this guide to create an Azure Red Hat OpenShift 4 cluster. If you have specific questions, please contact us
A job, in contrast to
replication controller, runs a pod with any number of replicas to completion. A
job tracks the overall progress of a task and updates its status with information
about active, succeeded, and failed pods. Deleting a job will clean up any pod
replicas it created. Jobs are part of the Kubernetes API, which can be managed
oc commands like other
Creating a Job
A job configuration consists of the following key parts:
A pod template, which describes the application the pod will create.
parallelism parameter, which specifies how many pod replicas running in parallel should execute a job. If not specified, this defaults to
the value in the
completions parameter, specifying how many concurrently running pods should execute a job. If not specified, this value defaults to one.
The following is an example of a
parallelism: 1 (1)
completions: 1 (2)
- name: pi
command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"]
restartPolicy: OnFailure (4)
Optional value for how many pod replicas a job should run in parallel; defaults to
Optional value for how many successful pod completions are needed to mark a job completed; defaults to one.
Template for the pod the controller creates.
The restart policy of the pod. This does not apply to the job controller. See Known Limitations for details.
You can also create and launch a job from a single command using
oc run. The following command creates and launches the same job as specified in the previous example:
$ oc run pi --image=perl --replicas=1 --restart=OnFailure \
--command -- perl -Mbignum=bpi -wle 'print bpi(2000)'
The job specification restart policy only applies to the pods, and not the job controller. However, the job controller is hard-coded to keep retrying jobs to completion.
restartPolicy: Never or
--restart=Never results in the same behavior as
restartPolicy: OnFailure or
--restart=OnFailure. That is, when a job fails it is restarted automatically until it succeeds (or is manually discarded). The policy only sets which subsystem performs the restart.
Never policy, the job controller performs the restart. With each attempt, the job controller increments the number of failures in the job status and create new pods. This means that with each failed attempt, the number of pods increases.
OnFailure policy, kubelet performs the restart. Each attempt does not increment the number of failures in the job status. In addition, kubelet will retry failed jobs starting pods on the same nodes.
Scaling a Job
A job can be scaled up or down by using the
oc scale command with the
--replicas option, which, in the case of jobs, modifies the
spec.parallelism parameter. This will result in modifying the number of pod
replicas running in parallel, executing a job.
The following command uses the example job above, and sets the
parameter to three:
$ oc scale job pi --replicas=3
Scaling replication controllers also uses the
oc scale command with the
--replicas option, but instead changes the
replicas parameter of a
replication controller configuration.
Setting Maximum Duration
When defining a
Job, you can define its maximum duration by setting
activeDeadlineSeconds field. It is specified in seconds and is not
set by default. When not set, there is no maximum duration enforced.
The maximum duration is counted from the time when a first pod gets scheduled in
the system, and defines how long a job can be active. It tracks overall time of
an execution and is irrelevant to the number of completions (number of pod replicas
needed to execute a task). After reaching the specified timeout, the job is
terminated by Azure Red Hat OpenShift.
The following example shows the part of a
activeDeadlineSeconds field for 30 minutes:
Job Backoff Failure Policy
A Job can be considered failed, after a set amount of retries due to a
logical error in configuration or other similar reasons. To specify the number
of retries for a job set the
.spec.backoffLimit property. This field defaults
to six. Failed Pods associated with the Job are recreated by the controller with an exponential backoff delay (
40s …) capped at six minutes. The limit is reset if no new failed pods appear between controller checks.