CronJob

    A CronJob creates Jobs on a repeating schedule.

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

    Caution:

    All CronJob schedule: times are based on the timezone of the kube-controller-manager.

    If your control plane runs the kube-controller-manager in Pods or bare containers, the timezone set for the kube-controller-manager container determines the timezone that the cron job controller uses.

    Caution:

    The does not officially support setting timezone as explained above.

    Setting variables such as CRON_TZ or TZ is not officially supported by the Kubernetes project. CRON_TZ or TZ is an implementation detail of the internal library being used for parsing and calculating the next Job creation time. Any usage of it is not recommended in a production cluster.

    When creating the manifest for a CronJob resource, make sure the name you provide is a valid DNS subdomain name. The name must be no longer than 52 characters. This is because the CronJob controller will automatically append 11 characters to the job name provided and there is a constraint that the maximum length of a Job name is no more than 63 characters.

    This example CronJob manifest prints the current time and a hello message every minute:

    (Running Automated Tasks with a CronJob takes you through this example in more detail).

    Cron schedule syntax

    For example, the line below states that the task must be started every Friday at midnight, as well as on the 13th of each month at midnight:

    0 0 13 * 5

    To generate CronJob schedule expressions, you can also use web tools like crontab.guru.

    For CronJobs with no time zone specified, the kube-controller-manager interprets schedules relative to its local time zone.

    FEATURE STATE: Kubernetes v1.25 [beta]

    If you enable the CronJobTimeZone feature gate, you can specify a time zone for a CronJob (if you don’t enable that feature gate, or if you are using a version of Kubernetes that does not have experimental time zone support, all CronJobs in your cluster have an unspecified timezone).

    A time zone database from the Go standard library is included in the binaries and used as a fallback in case an external database is not available on the system.

    A cron job creates a job object about once per execution time of its schedule. We say “about” because there are certain circumstances where two jobs might be created, or no job might be created. We attempt to make these rare, but do not completely prevent them. Therefore, jobs should be idempotent.

    If is set to a large value or left unset (the default) and if concurrencyPolicy is set to Allow, the jobs will always run at least once.

    Caution: If startingDeadlineSeconds is set to a value less than 10 seconds, the CronJob may not be scheduled. This is because the CronJob controller checks things every 10 seconds.

    For every CronJob, the CronJob Controller checks how many schedules it missed in the duration from its last scheduled time until now. If there are more than 100 missed schedules, then it does not start the job and logs the error.

    It is important to note that if the startingDeadlineSeconds field is set (not nil), the controller counts how many missed jobs occurred from the value of startingDeadlineSeconds until now rather than from the last scheduled time until now. For example, if startingDeadlineSeconds is 200, the controller counts how many missed jobs occurred in the last 200 seconds.

    A CronJob is counted as missed if it has failed to be created at its scheduled time. For example, if concurrencyPolicy is set to Forbid and a CronJob was attempted to be scheduled when there was a previous schedule still running, then it would count as missed.

    For example, suppose a CronJob is set to schedule a new Job every one minute beginning at , and its startingDeadlineSeconds field is not set. If the CronJob controller happens to be down from 08:29:00 to 10:21:00, the job will not start as the number of missed jobs which missed their schedule is greater than 100.

    To illustrate this concept further, suppose a CronJob is set to schedule a new Job every one minute beginning at 08:30:00, and its startingDeadlineSeconds is set to 200 seconds. If the CronJob controller happens to be down for the same period as the previous example (08:29:00 to 10:21:00,) the Job will still start at 10:22:00. This happens as the controller now checks how many missed schedules happened in the last 200 seconds (i.e., 3 missed schedules), rather than from the last scheduled time until now.

    Starting with Kubernetes v1.21 the second version of the CronJob controller is the default implementation. To disable the default CronJob controller and use the original CronJob controller instead, pass the CronJobControllerV2 feature gate flag to the , and set this flag to false. For example:

    • Read about the of CronJob .spec.schedule fields.
    • For instructions on creating and working with CronJobs, and for an example of a CronJob manifest, see Running automated tasks with CronJobs.
    • For instructions to clean up failed or completed jobs automatically, see