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* action page * change all page_title fields * update title * constraint through migrate pages * update page title and heading to use sentence case * fix front matter description * Apply suggestions from code review Co-authored-by: Jeff Boruszak <104028618+boruszak@users.noreply.github.com> --------- Co-authored-by: Jeff Boruszak <104028618+boruszak@users.noreply.github.com>
115 lines
2.7 KiB
Plaintext
115 lines
2.7 KiB
Plaintext
---
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layout: docs
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page_title: meta block in the job specification
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description: |-
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Define arbitrary metadata in the `meta` block of the Nomad job specification. Configure runtime environment variables for tasks to consume. Review examples that use Nomad interpolation and templates.
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---
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# `meta` block in the job specification
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<Placement
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groups={[
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['job', 'meta'],
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['job', 'group', 'meta'],
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['job', 'group', 'task', 'meta'],
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]}
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/>
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The `meta` block allows for user-defined arbitrary key-value pairs. It is
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possible to use the `meta` block at the [job][], [group][], or [task][] level.
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```hcl
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job "docs" {
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meta {
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my-key = "my-value"
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}
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group "example" {
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meta {
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my-key = "my-value"
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}
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task "server" {
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meta {
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my-key = "my-value"
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}
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}
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}
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}
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```
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Metadata is merged up the job specification, so metadata defined at the job
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level applies to all groups and tasks within that job. Metadata defined at the
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group layer applies to all tasks within that group.
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Meta values are made available inside tasks as [runtime environment variables][env_meta].
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## Parameters
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The "parameters" for the `meta` block can be any key-value. The keys and values
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are both of type `string`, but they can be specified as other types. They will
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automatically be converted to strings. Any character in a key other than
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`[A-Za-z0-9_.]` will be converted to `_`.
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## Examples
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The following examples only show the `meta` blocks. Remember that the
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`meta` block is only valid in the placements listed above.
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### Coercion
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This example shows the different ways to specify key-value pairs. Internally,
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these values will be stored as their string representation. No type information
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is preserved.
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```hcl
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meta {
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key = "true"
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key = true
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key = 1.4
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key = "1.4"
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}
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```
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### Interpolation
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This example shows using [Nomad interpolation][interpolation] to populate
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environment variables.
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```hcl
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meta {
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class = "${node.class}"
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}
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```
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### Meta keys with dots
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Meta keys that aren't valid HCLv2 identifiers, like ones containing `.`, require an alternative map assignment syntax.
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```hcl
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meta = {
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"project.team" = "sre"
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}
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```
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## Template usage example
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To make use of a `meta` value in a template, refer to its environment variable
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form.
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```hcl
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template {
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destination = "local/out.txt"
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data = <<EOH
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{{ env "NOMAD_META_mykey" }}
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EOH
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}
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```
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[job]: /nomad/docs/job-specification/job 'Nomad job Job Specification'
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[group]: /nomad/docs/job-specification/group 'Nomad group Job Specification'
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[task]: /nomad/docs/job-specification/task 'Nomad task Job Specification'
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[interpolation]: /nomad/docs/runtime/interpolation 'Nomad interpolation'
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[env_meta]: /nomad/docs/runtime/environment#meta-block-for-arbitrary-configuration
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