When the controller binds a PV to PVC, it saves both objects to etcd.
However, there is still an old version of these objects in the controller
Informer cache. So, when a new PVC comes, the PV is still seen as available
and may get bound to the new PVC. This will be blocked by etcd, still, it
creates unnecessary traffic that slows everything down.
Also, we save bound PV/PVC as two transactions - we save PV/PVC.Spec first
and then .Status. The controller gets "PV/PVC.Spec updated" event from etcd
and tries to fix the Status, as it seems to the controller it's outdated.
This write again fails - there already is a correct version in etcd.
We can't influence the Informer cache, it is read-only to the controller.
To prevent these useless writes to etcd, this patch introduces second cache
in the controller, which holds latest and greatest version on PVs and PVCs.
It gets updated with events from etcd *and* after etcd confirms successful
save of PV/PVC modified by the controller.
The cache stores only *pointers* to PVs/PVCs, so in ideal case it shares the
actual object data with the informer cache. They will diverge only when
the controller modifies something and the informer cache did not get update
events yet.
Using volume/claim.UID in the operation name is not really useful, as UIDs
are not logged by rest of the controller. On the other hand, volume.Name and
claim.Namespace/Name is logged pretty often and it would help to log these
also in operation name.
This has been already proven to be very useful in controller debugging.
Recycling is a long duration process and when the recycler controller is
restarted in the meantime, it should not start a new recycler pod if there is
one already running.
This means that the recycler pod must have deterministic name based on name
of the recycled PV, we then get name conflicts when creating the pod.
Two things need to be changed:
- recycler controller and recycler plugins must pass the PV.Name to place,
where the pod is created.
- create recycler pod with deterministic name and check "already exists" error.
When at it, remove useless 'resourceVersion' argument and make log messages
starting with lowercase.
Automatic merge from submit-queue
Refactor persistent volume controller
Here is complete persistent controller as designed in https://github.com/pmorie/pv-haxxz/blob/master/controller.go
It's feature complete and compatible with current binder/recycler/provisioner. No new features, it *should* be much more stable and predictable.
Testing
--
The unit test framework is quite complicated, still it was necessary to reach reasonable coverage (78% in `persistentvolume_controller.go`). The untested part are error cases, which are quite hard to test in reasonable way - sure, I can inject a VersionConflictError on any object update and check the error bubbles up to appropriate places, but the real test would be to run `syncClaim`/`syncVolume` again and check it recovers appropriately from the error in the next periodic sync. That's the hard part.
Organization
---
The PR starts with `rm -rf kubernetes/pkg/controller/persistentvolume`. I find it easier to read when I see only the new controller without old pieces scattered around.
[`types.go` from the old controller is reused to speed up matching a bit, the code looks solid and has 95% unit test coverage].
I tried to split the PR into smaller patches, let me know what you think.
~~TODO~~
--
* ~~Missing: provisioning, recycling~~.
* ~~Fix integration tests~~
* ~~Fix e2e tests~~
@kubernetes/sig-storage
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Fixes#15632
Automatic merge from submit-queue
Make name validators return string slices
Part of the larger validation PR, broken out for easier review and merge. Builds on previous PRs in the series.
- remove persistentvolume_ prefix from all files
- split controller.go into controller.go and controller_base.go (to have them
under 1500 lines for github)
This fixes e2e test for provisioning - it expects that provisioned volumes
are bound quickly.
Majority of this patch is update of test framework needs to initialize the
controller appropriately.
- Add reclaim policy to newVolume() call.
- Implement reactor Volumes().Get().
- Implement mock volume plugin.
- Add recycler tests.
- Add a synchronization condition to controller.scheduleOperation
- we need to pause the controller here, let the test to do some bad things
to the controller and test error cases in recycleVolumeOperation.
Test framework gets more and more complicated... But this is the last piece,
I promise.
We need to keep list of running recyclers, deleters and provisioners in
memory in order not to start a new recycling/deleting/provisioning twice
for the same volume/claim.
This will be eventually replaced by GoRoutineMap from PR #24838.
Automatic merge from submit-queue
prevent nil pointer when starting controllers before running the shar…
Fixes https://github.com/kubernetes/kubernetes/issues/25643.
https://github.com/kubernetes/kubernetes/pull/23795 changed initialization order, so the controller isn't guaranteed to be present at startup.
@mqliang @wojtek-t I'm pretty sure that we're not guaranteed to get back the correct `cache.Indexer` or `cache.Store` either. I'll look at re-plumbing the `AddIndexer` path to use the same instance so that its safe to use again.
