Chapter 29. Jobs
29.1. Overview
A job, in contrast to a replication controller, runs any number of pods 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 pods it created. Jobs are part of the extensions Kubernetes API, which can be managed with oc
commands like other object types.
See the Kubernetes documentation for more information about jobs.
29.2. Creating a Job
A job configuration consists of the following key parts:
- A pod template, which describes the application the pod will create.
-
An optional
parallelism
parameter, which specifies how many successful pod completions are needed to finish a job. If not specified, this defaults to the value in thecompletions
parameter. -
An optional
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 job
resource:
apiVersion: extensions/v1beta1 kind: Job metadata: name: pi spec: selector: 1 matchLabels: app: pi parallelism: 1 2 completions: 1 3 template: 4 metadata: name: pi labels: app: pi spec: containers: - name: pi image: perl command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"] restartPolicy: Never
- Label selector of the pod to run. It uses the generalized label selectors.
-
Optional value for how many pods a job should run concurrently, defaults to
completions
. - Optional value for how many successful pod completions is needed to mark a job completed, defaults to one.
- Template for the pod the controller creates.
29.3. Scaling a Job
A job can be scaled up or down by changing the parallelism
parameter accordingly. You can also use the oc scale
command with the --replicas
option, which, in the case of jobs, modifies the parallelism
parameter.
The following command uses the example job above, and sets the parallelism
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.