Without this error, kube-scheduler was simply ignoring the special
volume source and scheduled the pod. This was unlikely to work in
practice because the volume might have needed binding or the feature
is also disabled on kubelet which then doesn't know what to do with
the volume.
A CounterVector with status as label may create unnecessary overhead
and using the success case with the empty label value wasn't
easy. It's better to have two seperate counters, one for total number
of calls and one for failed calls.
As discussed during the production readiness review, a metric for the
PVC create operations is useful. The "ephemeral_volume" workqueue
metrics were already added in the initial implementation.
The new code follows the example set by the endpoints controller.
When the feature is disabled either in the scheduler or the CSIDriver,
the scheduler is expected to schedule pods without considering whether
storage capacity is available.
The goal of this move is related to issue 89930, to break the dependence
of scheduling plugins on internal helpers. This function can easily move to
component-helpers where it will be used by other components as well.
* Rename const for topology.../zone
* Rename const for topology.../region
* Rename const for failure-domain.../zone
* Rename const for failure-domain.../region
* Restore old names for compat
The main goal was to cover retrieval of a PVC from the apiserver when
it isn't known yet. This is achieved by adding PVCs and (for the sake
of completeness) PVs to the reactor, but not the controller, when a
special annotation is set. The approach with a special annotation was
chosen because it doesn't affect other tests.
The other test cases were added while checking the existing tests
because (at least at first glance) the situations seemed to be not
covered.
Normally, the PV controller knows about the PVC that triggers the
creation of a PV before it sees the PV, because the PV controller must
set the volume.beta.kubernetes.io/storage-provisioner annotation that
tells an external provisioner to create the PV.
When restarting, the PV controller first syncs its caches, so that
case is also covered.
However, the creator of a PVC might decided to set that annotation
itself to speed up volume creation. While unusual, it's not forbidden
and thus part of the external Kubernetes API. Whether it makes sense
depends on the intentions of the user.
When that is done and there is heavy load, an external provisioner
might see the PVC and create a PV before the PV controller sees the
PVC. If the PV controller then encounters the PV before the PVC, it
incorrectly concludes that the PV needs to be deleted instead of being
bound.
The same issue occurred earlier for external binding and the existing
code for looking up a PVC in the cache or in the apiserver solves the
issue also for volume provisioning, it just needs to be enabled also
for PVs without the pv.kubernetes.io/bound-by-controller annotation.
