If a GC claim is written and then volume is deleted before the `volumewatcher`
enters its run loop, we panic on the nil-pointer access. Simply doing a
nil-check at the top of the loop reveals a race condition around shutting down
the loop just as a new update is coming in.
Have the parent `volumeswatcher` send an initial update on the channel before
returning, so that we're still holding the lock. Update the watcher's `Stop`
method to set the running state, which lets us avoid having a second context and
makes stopping synchronous. This reduces the cases we have to handle in the run
loop.
Updated the tests now that we'll safely return from the goroutine and stop the
runner in a larger set of cases. Ran the tests with the `-race` detection flag
and fixed up any problems found here as well.
The volume watcher design was based on deploymentwatcher and drainer,
but has an important difference: we don't want to maintain a goroutine
for the lifetime of the volume. So we stop the volumewatcher goroutine
for a volume when that volume has no more claims to free. But the
shutdown races with updates on the parent goroutine, and it's possible
to drop updates. Fortunately these updates are picked up on the next
core GC job, but we're most likely to hit this race when we're
replacing an allocation and that's the time we least want to wait.
Wait until the volume has "settled" before stopping this goroutine so
that the race between shutdown and the parent goroutine sending on
`<-updateCh` is pushed to after the window we most care about quick
freeing of claims.
* Fixes a resource leak when volumewatchers are no longer needed. The
volume is nil and can't ever be started again, so the volume's
`watcher` should be removed from the top-level `Watcher`.
* De-flakes the GC job test: the test throws an error because the
claimed node doesn't exist and is unreachable. This flaked instead of
failed because we didn't correctly wait for the first pass through the
volumewatcher.
Make the GC job wait for the volumewatcher to reach the quiescent
timeout window state before running the GC eval under test, so that
we're sure the GC job's work isn't being picked up by processing one
of the earlier claims. Update the claims used so that we're sure the
GC pass won't hit a node unpublish error.
* Adds trace logging to unpublish operations
* lint: require should not be aliased in core_sched_test
* lint: require should not be aliased in volumes_watcher_test
* testing: don't alias state package in core_sched_test
CSI `CreateVolume` RPC is idempotent given that the topology,
capabilities, and parameters are unchanged. CSI volumes have many
user-defined fields that are immutable once set, and many fields that
are not user-settable.
Update the `Register` RPC so that updating a volume via the API merges
onto any existing volume without touching Nomad-controlled fields,
while validating it with the same strict requirements expected for
idempotent `CreateVolume` RPCs.
Also, clarify that this state store method is used for everything, not just
for the `Register` RPC.
The volumewatcher test incorrectly represents the change in attachment
and access modes introduced in Nomad 1.1.0 to support volume
creation. This leads to a test that happens to pass but only
accidentally.
Update the test to correctly represent the volume modes set by the
existing claims on the test volumes.
* The volume claim GC method and volumewatcher both have logic
collecting terminal allocations that duplicates most of the logic
that's now in the state store's `CSIVolumeDenormalize` method. Copy
this logic into the state store so that all code paths have the same
view of the past claims.
* Remove logic in the volume claim GC that now lives in the state
store's `CSIVolumeDenormalize` method.
* Remove logic in the volumewatcher that now lives in the state
store's `CSIVolumeDenormalize` method.
* Remove logic in the node unpublish RPC that now lives in the state
store's `CSIVolumeDenormalize` method.
* csi: resolve invalid claim states on read
It's currently possible for CSI volumes to be claimed by allocations
that no longer exist. This changeset asserts a reasonable state at
the state store level by registering these nil allocations as "past
claims" on any read. This will cause any pass through the periodic GC
or volumewatcher to trigger the unpublishing workflow for those claims.
* csi: make feasibility check errors more understandable
When the feasibility checker finds we have no free write claims, it
checks to see if any of those claims are for the job we're currently
scheduling (so that earlier versions of a job can't block claims for
new versions) and reports a conflict if the volume can't be scheduled
so that the user can fix their claims. But when the checker hits a
claim that has a GCd allocation, the state is recoverable by the
server once claim reaping completes and no user intervention is
required; the blocked eval should complete. Differentiate the
scheduler error produced by these two conditions.
The volumewatcher that runs on the leader needs to make RPC calls
rather than writing to raft (as we do in the deploymentwatcher)
because the unpublish workflow needs to make RPC calls to the
clients. This requires that the volumewatcher has access to the
leader's ACL token.
But when leadership transitions, the new leader creates a new leader
ACL token. This ACL token needs to be passed into the volumewatcher
when we enable it, otherwise the volumewatcher can find itself with a
stale token.
When `volumewatcher.Watcher` starts on the leader, it starts a watch
on every volume and triggers a reap of unused claims on any change to
that volume. But if a reaping is in-flight during leadership
transitions, it will fail and the event that triggered the reap will
be dropped. Perform one reap of unused claims at the start of the
watcher so that leadership transitions don't drop this event.
The unpublish workflow requires that we know the mode (RW vs RO) if we want to
unpublish the node. Update the hook and the Unpublish RPC so that we mark the
claim for release in a new state but leave the mode alone. This fixes a bug
where RO claims were failing node unpublish.
The core job GC doesn't know the mode, but we don't need it for that workflow,
so add a mode specifically for GC; the volumewatcher uses this as a sentinel
to check whether claims (with their specific RW vs RO modes) need to be claimed.
* use msgtype in upsert node
adds message type to signature for upsert node, update tests, remove placeholder method
* UpsertAllocs msg type test setup
* use upsertallocs with msg type in signature
update test usage of delete node
delete placeholder msgtype method
* add msgtype to upsert evals signature, update test call sites with test setup msg type
handle snapshot upsert eval outside of FSM and ignore eval event
remove placeholder upsertevalsmsgtype
handle job plan rpc and prevent event creation for plan
msgtype cleanup upsertnodeevents
updatenodedrain msgtype
msg type 0 is a node registration event, so set the default to the ignore type
* fix named import
* fix signature ordering on upsertnode to match
If a volume GC and a `nomad volume detach` command land concurrently, we can
end up with multiple claims without an allocation, which results in extra
no-op work when finding claims to collect as past claims.
Add a Postrun hook to send the `CSIVolume.Unpublish` RPC to the server. This
may forward client RPCs to the node plugins or to the controller plugins,
depending on whether other allocations on this node have claims on this
volume.
By making clients responsible for running the `CSIVolume.Unpublish` RPC (and
making the RPC available to a `nomad volume detach` command), the
volumewatcher becomes only used by the core GC job and we no longer need
async volume GC from job deregister and node update.
This changeset updates `nomad/volumewatcher` to take advantage of the
`CSIVolume.Unpublish` RPC. This lets us eliminate a bunch of code and
associated tests. The raft batching code can be safely dropped, as the
characteristic times of the CSI RPCs are on the order of seconds or even
minutes, so batching up raft RPCs added complexity without any real world
performance wins.
Includes refactor w/ test cleanup and dead code elimination in volumewatcher
The `nomad volume deregister` command currently returns an error if the volume
has any claims, but in cases where the claims can't be dropped because of
plugin errors, providing a `-force` flag gives the operator an escape hatch.
If the volume has no allocations or if they are all terminal, this flag
deletes the volume from the state store, immediately and implicitly dropping
all claims without further CSI RPCs. Note that this will not also
unmount/detach the volume, which we'll make the responsibility of a separate
`nomad volume detach` command.
The volumewatcher restores itself on notification, but detecting this is racy
because it may reap any claim (or find there are no claims to reap) and
shutdown before we can test whether it's running. This appears to have become
flaky with a new version of golang. The other cases in this test case
sufficiently exercise the start/stop behavior of the volumewatcher, so remove
the flaky section.
CSI plugins can require credentials for some publishing and
unpublishing workflow RPCs. Secrets are configured at the time of
volume registration, stored in the volume struct, and then passed
around as an opaque map by Nomad to the plugins.
The watcher goroutines will be automatically started if a volume has
updates, but when idle we shouldn't keep a goroutine running and
taking up memory.
The `volumewatcher` has a 250ms batch window so claim updates will not
typically be large enough to risk exceeding the maximum raft message
size. But large jobs might have enough volume claims that this could
be a danger. Set a maximum batch size of 100 messages per
batch (roughly 33K), as a very conservative safety/robustness guard.
Co-authored-by: Chris Baker <1675087+cgbaker@users.noreply.github.com>
* volumewatcher: remove redundant log fields
The constructor for `volumeWatcher` already sets a `logger.With` that
includes the volume ID and namespace fields. Remove them from the
various trace logs.
* volumewatcher: advance state for controller already released
One way of bypassing client RPCs in testing is to set a claim status
to controller-detached, but this results in an incorrect claim state
when we checkpoint.
The nil-check here is left-over from an earlier approach that didn't
get merged. It doesn't do anything for us now as we can't ever pass it
`nil` and if we leave it in the `getVolume` call it guards will panic
anyways.
We should only remove the `ReadAllocs`/`WriteAllocs` values for a
volume after the claim has entered the "ready to free"
state. The volume will eventually be released as expected. But
querying the volume API will show the volume is released before the
controller unpublish has finished and this can cause a race with
starting new jobs.
Test updates are to cover cases where we're dropping claims but not
running through the whole reaping process.
This changeset adds a subsystem to run on the leader, similar to the
deployment watcher or node drainer. The `Watcher` performs a blocking
query on updates to the `CSIVolumes` table and triggers reaping of
volume claims.
This will avoid tying up scheduling workers by immediately sending
volume claim workloads into their own loop, rather than blocking the
scheduling workers in the core GC job doing things like talking to CSI
controllers
The volume watcher is enabled on leader step-up and disabled on leader
step-down.
The volume claim GC mechanism now makes an empty claim RPC for the
volume to trigger an index bump. That in turn unblocks the blocking
query in the volume watcher so it can assess which claims can be
released for a volume.
