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docs: clean up explanation of volume per_alloc

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Tim Gross 2021-04-09 10:58:25 -04:00 committed by Tim Gross
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commit fd3d443863
1 changed files with 11 additions and 21 deletions
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website/content/docs/job-specification/volume.mdx
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@ -111,22 +111,12 @@ The following fields are only valid for volumes with `type = "csi"`:
## Volume Interpolation
Because volumes represent state, many workloads with multiple allocations will
want to mount specific volumes to specific tasks. You can use the [HCL2]
syntax in Nomad 1.0 for fine-grained control over how volumes are used.
There are two limitations to using HCL2 interpolation for `volume` blocks:
- The `volume` block is used to schedule workloads, so any interpolation needs
to be done before placement. This means that variables like
`NOMAD_ALLOC_INDEX` can't be used for interpolation. Use the `per_alloc`
field described above.
- Nomad does not yet support dynamic volume creation (see [GH-8212]), so volumes
must be created and registered before being used as a `volume.source`.
The following job specification demonstrates how to use multiple volumes with
multiple allocations, using the `per_alloc` field. This job specification also
shows using HCL2 -variables interpolation to expose information to the task's
environment.
want to mount specific volumes to specific tasks. The `volume` block is used
to schedule workloads, so `${NOMAD_ALLOC_INDEX}` can't be used directly in the
`volume.source` field. The following job specification demonstrates how to use
multiple volumes with multiple allocations, using the `per_alloc` field. This
job specification also shows using HCL2 -variables interpolation to expose
information to the task's environment.
```hcl
variables {
@ -141,9 +131,11 @@ job "example" {
count = 2
volume "cache-volume" {
type = "csi"
source = "test-volume"
per_alloc = true
type = "csi"
source = "test-volume"
attachment_mode = "file-system"
access_mode = "single-node-writer"
per_alloc = true
}
network {
@ -212,5 +204,3 @@ ID Node ID Task Group Version Desired Status Created Modified
[csi_volume]: /docs/commands/volume/register
[attachment mode]: /docs/commands/volume/register#attachment_mode
[volume registration]: /docs/commands/volume/register#mount_options
[hcl2]: /docs/job-specification/hcl2
[gh-8212]: https://github.com/hashicorp/nomad/issues/8212