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and tries to fix the Status, as it seems to the controller it's outdated.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.
- remove persistentvolume_ prefix from all files
- split controller.go into controller.go and controller_base.go (to have them
under 1500 lines for github)
