periodic block in the job specification

The periodic block allows a job to run at fixed times, dates, or intervals. The easiest way to think about the periodic scheduler is "Nomad cron" or "distributed cron".

job "docs" {
  periodic {
    cron             = "*/15 * * * * *"
    prohibit_overlap = true
  }
}

The periodic expression by default evaluates in the UTC timezone to ensure consistent evaluation when Nomad spans multiple time zones.

Requirements

• The job's scheduler type must be batch or sysbatch.
• A job can not be updated to be periodically. Thus, to transition an existing job to be periodic, you must first run nomad stop -purge «job name». This is expected behavior and is to ensure that this change has been intentionally made by an operator.

Refer to the parameterized documentation for how to use parameters with a periodic job.

Parameters

• cron (deprecated: Replaced by crons in 1.6.2) (string) - Specifies a cron expression configuring the interval to launch the job. In addition to cron-specific formats, this option also includes predefined expressions such as @daily or @weekly. Either cron or crons must be set, but not both.

• crons - A list of cron expressions configuring the intervals the job is launched at. The job runs at the next earliest time that matches any of the expressions. Supports predefined expressions such as @daily and @weekly. Refer to the documentation for full details about the supported cron specs and the predefined expressions. Either cron or crons must be set, but not both.

• prohibit_overlap (bool: false) - Specifies if this job should wait until previous instances of this job have completed. This only applies to this job; it does not prevent other periodic jobs from running at the same time.

• time_zone (string: "UTC") - Specifies the time zone to evaluate the next launch interval against. Daylight Saving Time affects scheduling, so please ensure the behavior below meets your needs. The time zone must be parsable by Golang's LoadLocation.

• enabled (bool: true) - Specifies if this job should run. This not only prevents this job from running on the cron schedule but prevents force launches.

Examples

The following examples only show the periodic blocks. Remember that the periodic block is only valid in the placements listed above.

Run daily

This example shows running a periodic job daily:

periodic {
  cron = "@daily"
}

Set time zone

This example shows setting a time zone for the periodic job to evaluate in:

periodic {
  cron      = "*/15 * * * * *"
  time_zone = "America/New_York"
}

Run multiple crons

periodic {
  crons = [
    "*/5 * * *",
    "*/7 * * *"
  ]
  time_zone = "America/New_York"
}

Daylight saving time

Though Nomad supports configuring time_zone, we strongly recommend that periodic jobs are specified with respect to UTC time_zone. Only customize time_zone when the following daylight saving time behavior is desired:

• When leaping forward, periodic jobs scheduled for the skipped hour (eg 2:30am in America/New_York) will be skipped for that day (eg March 10th).

• When falling back, periodic jobs scheduled for the duplicated hour (eg 1:30am in America/New_York) will be run twice for that day (eg November 3rd).

See the multiregion documentation for additional considerations when configuring time zones for periodic jobs.