CSI volumes are namespaced. But the client does not include the namespace in the
staging mount path. This causes CSI volumes with the same volume ID but
different namespace to collide if they happen to be placed on the same host. The
per-allocation paths don't need to be namespaced, because an allocation can only
mount volumes from its job's own namespace.
Rework the CSI hook tests to have more fine-grained control over the mock
on-disk state. Add tests covering upgrades from staging paths missing
namespaces.
Fixes: https://github.com/hashicorp/nomad/issues/18741
If a volume-claiming alloc stops and the CSI Node plugin that serves
that alloc's volumes is missing, there's no way for the allocrunner
hook to send the `NodeUnpublish` and `NodeUnstage` RPCs.
This changeset addresses this issue with a redesign of the client-side
for CSI. Rather than unmounting in the alloc runner hook, the alloc
runner hook will simply exit. When the server gets the
`Node.UpdateAlloc` for the terminal allocation that had a volume claim,
it creates a volume claim GC job. This job will made client RPCs to a
new node plugin RPC endpoint, and only once that succeeds, move on to
making the client RPCs to the controller plugin. If the node plugin is
unavailable, the GC job will fail and be requeued.
