This commit introduces support for staging volumes when a plugin
implements the STAGE_UNSTAGE_VOLUME capability.
See the following for further reference material:
4731db0e0b/spec.md (nodestagevolume)
This commit adds helpers that create and validate the staging directory
for a given volume. It is currently missing usage options as the
interfaces are not yet in place for those.
The staging directory is only required when a volume has the
STAGE_UNSTAGE Volume capability and has to live within the plugin root
as the plugin needs to be able to create mounts inside it from within
the container.
This changeset is some pre-requisite boilerplate that is required for
introducing CSI volume management for client nodes.
It extracts out fingerprinting logic from the csi instance manager.
This change is to facilitate reusing the csimanager to also manage the
node-local CSI functionality, as it is the easiest place for us to
guaruntee health checking and to provide additional visibility into the
running operations through the fingerprinter mechanism and goroutine.
It also introduces the VolumeMounter interface that will be used to
manage staging/publishing unstaging/unpublishing of volumes on the host.
