open-nomad/website/source/docs/job-specification/reschedule.html.md

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docs	reschedule Stanza - Job Specification	docs-job-specification-reschedule	The "reschedule" stanza specifies the group's rescheduling strategy upon allocation failures. Nomad will only attempt to reschedule failed allocations on to another node only after any local [restarts](docs/job-specification/restart.html) have been exceeded.

reschedule Stanza

Placement	job -> **reschedule** job -> group -> **reschedule**

The reschedule stanza specifies the group's rescheduling strategy. If specified at the job level, the configuration will apply to all groups within the job. If the reschedule stanza is present on both the job and the group, they are merged with the group stanza taking the highest precedence and then the job.

Nomad will attempt to schedule the task on another node if any of its allocation statuses become "failed". It prefers to create a replacement allocation on a node that hasn't previously been used.

job "docs" {
  group "example" {
    reschedule {
      attempts       = 15
      interval       = "1h"
      delay          = "30s"
      delay_function = "exponential"
      max_delay      = "120s"
      unlimited      = false
    }
  }
}

~> The reschedule stanza does not apply to system jobs because they run on every node.

reschedule Parameters

• attempts (int: <varies>) - Specifies the number of reschedule attempts allowed in the configured interval. Defaults vary by job type, see below for more information.

• interval (string: <varies>) - Specifies the sliding window which begins when the first reschedule attempt starts and ensures that only attempts number of reschedule happen within it. If more than attempts number of failures happen with this interval, Nomad will not reschedule any more.

• delay (string: <varies>) - Specifies the duration to wait before attempting to reschedule a failed task. This is specified using a label suffix like "30s" or "1h".

• delay_function (string: <varies>) - Specifies the function that is used to calculate subsequent reschedule delays. The initial delay is specified by the delay parameter. delay_function has three possible values which are described below.

  • constant - The delay between reschedule attempts stays constant at the delay value.
  • exponential - The delay between reschedule attempts doubles.
  • fibonacci - The delay between reschedule attempts is calculated by adding the two most recent delays applied. For example if delay is set to 5 seconds, the next five reschedule attempts will be delayed by 5 seconds, 5 seconds, 10 seconds, 15 seconds, and 25 seconds respectively.

• max_delay (string: <varies>) - is an upper bound on the delay beyond which it will not increase. This parameter is used when delay_function is exponential or fibonacci, and is ignored when constant delay is used.

• unlimited (boolean:<varies>) - unlimited enables unlimited reschedule attempts. If this is set to true the attempts and interval fields are not used.

Information about reschedule attempts are displayed in the CLI and API for allocations. Rescheduling is enabled by default for service and batch jobs with the options shown below.

reschedule Parameter Defaults

The values for the reschedule parameters vary by job type. Below are the defaults by job type:

• The Default Batch Reschedule Policy is:

  reschedule {
    attempts       = 1
    interval       = "24h"
    unlimited      = false
    delay          = "5s"
    delay_function = "constant"
  }
  

• The Default Service Reschedule Policy is:

  reschedule {
   delay          = "30s"
   delay_function = "exponential"
   max_delay      = "1h"
   unlimited      = true
  }
  

Rescheduling during deployments

The update stanza controls rolling updates and canary deployments. A task group's reschedule stanza does not take affect during a deployment. For example, if a new version of the job is rolled out and the deployment failed due to a failing allocation, Nomad will not reschedule it.

Disabling rescheduling

To disable rescheduling, set the attempts parameter to zero and unlimited to false.

job "docs" {
  group "example" {
    reschedule {
      attempts  = 0
      unlimited = false
    }
  }
}