Allow for faster updates to plugin status when allocations become
terminal by listening for register/deregister events from the dynamic
plugin registry (which in turn are triggered by the plugin supervisor
hook).
The deregistration function closures that we pass up to the CSI plugin
manager don't properly close over the name and type of the
registration, causing monolith-type plugins to deregister only one of
their two plugins on alloc shutdown. Rebind plugin supervisor
deregistration targets to fix that.
Includes log message and comment improvements
In order to correctly fingerprint dynamic plugins on client restarts,
we need to persist a handle to the plugin (that is, connection info)
to the client state store.
The dynamic registry will sync automatically to the client state
whenever it receives a register/deregister call.
This changeset implements the initial registration and fingerprinting
of CSI Plugins as part of #5378. At a high level, it introduces the
following:
* A `csi_plugin` stanza as part of a Nomad task configuration, to
allow a task to expose that it is a plugin.
* A new task runner hook: `csi_plugin_supervisor`. This hook does two
things. When the `csi_plugin` stanza is detected, it will
automatically configure the plugin task to receive bidirectional
mounts to the CSI intermediary directory. At runtime, it will then
perform an initial heartbeat of the plugin and handle submitting it to
the new `dynamicplugins.Registry` for further use by the client, and
then run a lightweight heartbeat loop that will emit task events
when health changes.
* The `dynamicplugins.Registry` for handling plugins that run
as Nomad tasks, in contrast to the existing catalog that requires
`go-plugin` type plugins and to know the plugin configuration in
advance.
* The `csimanager` which fingerprints CSI plugins, in a similar way to
`drivermanager` and `devicemanager`. It currently only fingerprints
the NodeID from the plugin, and assumes that all plugins are
monolithic.
Missing features
* We do not use the live updates of the `dynamicplugin` registry in
the `csimanager` yet.
* We do not deregister the plugins from the client when they shutdown
yet, they just become indefinitely marked as unhealthy. This is
deliberate until we figure out how we should manage deploying new
versions of plugins/transitioning them.
Tim Gross