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@ -9,16 +9,22 @@ assignees:
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* TOC
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{:toc}
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## What is a _Scheduled Job_?
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## What is a _Cron Job_?
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A _Scheduled Job_ manages time based [Jobs](/docs/user-guide/jobs/), namely:
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A _Cron Job_ manages time based [Jobs](/docs/user-guide/jobs/), namely:
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* Once at a specified point in time
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* Repeatedly at a specified point in time
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One ScheduledJob object is like one line of a _crontab_ (cron table) file. It runs a job periodically
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One CronJob object is like one line of a _crontab_ (cron table) file. It runs a job periodically
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on a given schedule, written in [Cron](https://en.wikipedia.org/wiki/Cron) format.
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**Note:**: The question mark (`?`) in the schedule has the same meaning as an asterisk `*`,
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that is, it stands for any of available value for a given field.
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**Note:**: ScheduledJob resource was introduced in Kubernetes version 1.4, but starting
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from version 1.5 its current name is CronJob.
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A typical use case is:
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* Schedule a job execution at a given point in time.
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@ -26,38 +32,38 @@ A typical use case is:
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### Prerequisites
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You need a working Kubernetes cluster at version >= 1.4, with batch/v2alpha1 API turned on by passing
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`--runtime-config=batch/v2alpha1` while bringing up the API server (see [Turn on or off an API version
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for your cluster](/docs/admin/cluster-management/#turn-on-or-off-an-api-version-for-your-cluster) for
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more). You cannot use Scheduled Jobs on a hosted Kubernetes provider that has disabled alpha resources.
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You need a working Kubernetes cluster at version >= 1.4 (for ScheduledJob), >= 1.5 (for CronJobs),
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with batch/v2alpha1 API turned on by passing `--runtime-config=batch/v2alpha1` while bringing up
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the API server (see [Turn on or off an API version for your cluster](/docs/admin/cluster-management/#turn-on-or-off-an-api-version-for-your-cluster)
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for more). You cannot use Cron Jobs on a hosted Kubernetes provider that has disabled alpha resources.
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## Creating a Scheduled Job
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## Creating a Cron Job
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Here is an example Scheduled Job. Every minute, it runs a simple job to print current time and then say
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Here is an example Cron Job. Every minute, it runs a simple job to print current time and then say
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hello.
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{% include code.html language="yaml" file="sj.yaml" ghlink="/docs/user-guide/sj.yaml" %}
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{% include code.html language="yaml" file="cronjob.yaml" ghlink="/docs/user-guide/cronjob.yaml" %}
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Run the example scheduled job by downloading the example file and then running this command:
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Run the example cron job by downloading the example file and then running this command:
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```shell
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$ kubectl create -f ./sj.yaml
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scheduledjob "hello" created
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$ kubectl create -f ./cronjob.yaml
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cronjob "hello" created
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```
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Alternatively, use `kubectl run` to create a scheduled job without writing full config:
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Alternatively, use `kubectl run` to create a cron job without writing full config:
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```shell
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$ kubectl run hello --schedule="0/1 * * * ?" --restart=OnFailure --image=busybox -- /bin/sh -c "date; echo Hello from the Kubernetes cluster"
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scheduledjob "hello" created
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$ kubectl run hello --schedule="*/1 * * * *" --restart=OnFailure --image=busybox -- /bin/sh -c "date; echo Hello from the Kubernetes cluster"
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cronjob "hello" created
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```
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After creating the scheduled job, get its status using this command:
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After creating the cron job, get its status using this command:
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```shell
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$ kubectl get scheduledjob hello
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$ kubectl get cronjob hello
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NAME SCHEDULE SUSPEND ACTIVE LAST-SCHEDULE
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hello 0/1 * * * ? False 0 <none>
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hello */1 * * * * False 0 <none>
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```
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As you can see above, there's no active job yet, and no job has been scheduled, either.
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@ -70,12 +76,12 @@ NAME DESIRED SUCCESSFUL AGE
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hello-4111706356 1 1 2s
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```
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Now you've seen one running job scheduled by "hello". We can stop watching it and get the scheduled job again:
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Now you've seen one running job scheduled by "hello". We can stop watching it and get the cron job again:
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```shell
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$ kubectl get scheduledjob hello
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$ kubectl get cronjob hello
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NAME SCHEDULE SUSPEND ACTIVE LAST-SCHEDULE
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hello 0/1 * * * ? False 0 Mon, 29 Aug 2016 14:34:00 -0700
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hello */1 * * * * False 0 Mon, 29 Aug 2016 14:34:00 -0700
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```
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You should see that "hello" successfully scheduled a job at the time specified in `LAST-SCHEDULE`. There are
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@ -96,17 +102,17 @@ Mon Aug 29 21:34:09 UTC 2016
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Hello from the Kubernetes cluster
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```
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## Deleting a Scheduled Job
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## Deleting a Cron Job
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Once you don't need a scheduled job anymore, simply delete it with `kubectl`:
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Once you don't need a cron job anymore, simply delete it with `kubectl`:
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```shell
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$ kubectl delete scheduledjob hello
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scheduledjob "hello" deleted
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$ kubectl delete cronjob hello
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cronjob "hello" deleted
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```
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This stops new jobs from being created. However, running jobs won't be stopped, and no jobs or their pods will
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be deleted. To clean up those jobs and pods, you need to list all jobs created by the scheduled job, and delete them all:
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be deleted. To clean up those jobs and pods, you need to list all jobs created by the cron job, and delete them all:
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```shell
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$ kubectl get jobs
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@ -121,29 +127,29 @@ job "hello-1202039034" deleted
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...
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```
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Once the jobs are deleted, the pods created by them are deleted as well. Note that all jobs created by scheduled
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Once the jobs are deleted, the pods created by them are deleted as well. Note that all jobs created by cron
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job "hello" will be prefixed "hello-". You can delete them at once with `kubectl delete jobs --all`, if you want to
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delete all jobs in the current namespace (not just the ones created by "hello".)
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## Scheduled Job Limitations
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## Cron Job Limitations
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A scheduled job creates a job object _about_ once per execution time of its schedule. We say "about" because there
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A cron job creates a job object _about_ once per execution time of its schedule. We say "about" because there
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are certain circumstances where two jobs might be created, or no job might be created. We attempt to make these rare,
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but do not completely prevent them. Therefore, jobs should be _idempotent_.
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The job is responsible for retrying pods, parallelism among pods it creates, and determining the success or failure
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of the set of pods. A scheduled job does not examine pods at all.
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of the set of pods. A cron job does not examine pods at all.
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## Writing a Scheduled Job Spec
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## Writing a Cron Job Spec
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As with all other Kubernetes configs, a scheduled job needs `apiVersion`, `kind`, and `metadata` fields. For general
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As with all other Kubernetes configs, a cron job needs `apiVersion`, `kind`, and `metadata` fields. For general
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information about working with config files, see [deploying applications](/docs/user-guide/deploying-applications),
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[configuring containers](/docs/user-guide/configuring-containers), and
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[using kubectl to manage resources](/docs/user-guide/working-with-resources) documents.
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A scheduled job also needs a [`.spec` section](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/docs/devel/api-conventions.md#spec-and-status).
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A cron job also needs a [`.spec` section](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/docs/devel/api-conventions.md#spec-and-status).
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**Note:** All modifications to a scheduled job, especially its `.spec`, will be applied only to the next run.
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**Note:** All modifications to a cron job, especially its `.spec`, will be applied only to the next run.
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### Schedule
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@ -165,14 +171,14 @@ there's no deadline.
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### Concurrency Policy
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The `.spec.concurrencyPolicy` field is also optional. It specifies how to treat concurrent executions of a job
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created by this scheduled job. Only one of the following concurrent policies may be specified:
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created by this cron job. Only one of the following concurrent policies may be specified:
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* `Allow` (default): allows concurrently running jobs
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* `Forbid`: forbids concurrent runs, skipping next run if previous hasn't finished yet
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* `Replace`: cancels currently running job and replaces it with a new one
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Note that concurrency policy only applies to the jobs created by the same scheduled job. If there are multiple
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scheduled jobs, their respective jobs are always allowed to run concurrently.
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Note that concurrency policy only applies to the jobs created by the same cron job. If there are multiple
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cron jobs, their respective jobs are always allowed to run concurrently.
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### Suspend
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Jared
GitHub