133 lines
4.6 KiB
Markdown
133 lines
4.6 KiB
Markdown
---
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layout: "docs"
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page_title: "reschedule Stanza - Job Specification"
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sidebar_current: "docs-job-specification-reschedule"
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description: |-
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The "reschedule" stanza specifies the group's rescheduling strategy upon
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allocation failures. Nomad will only attempt to reschedule failed allocations on
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to another node only after any local [restarts](docs/job-specification/restart.html)
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have been exceeded.
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---
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# `reschedule` Stanza
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<table class="table table-bordered table-striped">
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<tr>
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<th width="120">Placement</th>
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<td>
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<code>job -> **reschedule**</code>
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<br>
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<code>job -> group -> **reschedule**</code>
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</td>
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</tr>
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</table>
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The `reschedule` stanza specifies the group's rescheduling strategy. If specified at the job
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level, the configuration will apply to all groups within the job. If the
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reschedule stanza is present on both the job and the group, they are merged with
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the group stanza taking the highest precedence and then the job.
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Nomad will attempt to schedule the task on another node if any of its allocation
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statuses become "failed". It prefers to create a replacement allocation on a node
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that hasn't previously been used.
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```hcl
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job "docs" {
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group "example" {
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reschedule {
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attempts = 15
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interval = "1hr"
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delay = "30s"
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delay_function = "exponential"
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max_delay = "120s"
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unlimited = false
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}
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}
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}
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```
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~> The reschedule stanza does not apply to `system` jobs because they run on
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every node.
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## `reschedule` Parameters
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- `attempts` `(int: <varies>)` - Specifies the number of reschedule attempts
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allowed in the configured interval. Defaults vary by job type, see below
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for more information.
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- `interval` `(string: <varies>)` - Specifies the sliding window which begins
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when the first reschedule attempt starts and ensures that only `attempts`
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number of reschedule happen within it. If more than `attempts` number of
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failures happen with this interval, Nomad will not reschedule any more.
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- `delay` `(string: <varies>)` - Specifies the duration to wait before attempting
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to reschedule a failed task. This is specified using a label suffix like "30s" or "1h".
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- `delay_function` `(string: <varies>)` - Specifies the function that is used to
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calculate subsequent reschedule delays. The initial delay is specified by the delay parameter.
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`delay_function` has three possible values which are described below.
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- `constant` - The delay between reschedule attempts stays constant at the `delay` value.
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- `exponential` - The delay between reschedule attempts doubles.
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- `fibonacci` - The delay between reschedule attempts is calculated by adding the two most recent
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delays applied. For example if `delay` is set to 5 seconds, the next five reschedule attempts will be
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delayed by 5 seconds, 5 seconds, 10 seconds, 15 seconds, and 25 seconds respectively.
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- `max_delay` `(string: <varies>)` - is an upper bound on the delay beyond which it will not increase. This parameter
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is used when `delay_function` is `exponential` or `fibonacci`, and is ignored when `constant` delay is used.
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- `unlimited` `(boolean:<varies>)` - `unlimited` enables unlimited reschedule attempts. If this is set to true
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the `attempts` and `interval` fields are not used.
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Information about reschedule attempts are displayed in the CLI and API for
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allocations. Rescheduling is enabled by default for service and batch jobs
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with the options shown below.
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### `reschedule` Parameter Defaults
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The values for the `reschedule` parameters vary by job type. Below are the
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defaults by job type:
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- The Default Batch Reschedule Policy is:
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```hcl
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reschedule {
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attempts = 1
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interval = "24h"
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unlimited = false
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delay = "5s"
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delay_function = "constant"
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}
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```
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- The Default Service Reschedule Policy is:
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```hcl
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reschedule {
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delay = "30s"
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delay_function = "exponential"
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max_delay = "1hr"
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unlimited = true
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}
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```
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### Rescheduling during deployments
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The [update stanza](docs/job-specification/update.html) controls rolling updates and canary deployments. A task
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group's reschedule stanza does not take affect during a deployment. For example, if a new version of the job
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is rolled out and the deployment failed due to a failing allocation, Nomad will not reschedule it.
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### Disabling rescheduling ###
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To disable rescheduling, set the `attempts` parameter to zero and `unlimited` to false.
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```hcl
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job "docs" {
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group "example" {
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reschedule {
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attempts = 0
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unlimited = false
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}
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}
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}
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```
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