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5643b7498f
Automatic merge from submit-queue volume controller: Add cache with the latest version of PVs and PVCs 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. To make everything worse, when periodic sync with the old PVC is performed, this PVC is seen by the controller as Pending (while it's already Bound on etcd) and will be bound to a different PV. Writing to this PV won't be blocked by etcd, only subsequent write of the PVC fails. So, the controller will need to roll back the PV in another transaction(s). The controller can keep itself pretty busy this way. Also, we save bound PVs (and PVCs) as two transactions - we save say PV.Spec first and then .Status. The controller gets "PV.Spec updated" event from etcd and tries to fix the Status, as it seems to the controller it's outdated.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. As we can't influence the Informer cache, it is read-only to the controller, this patch introduces second cache in the controller, which holds latest and greatest version on PVs and PVCs to prevent these useless writes to etcd . 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 for a short time when the controller modifies something and the informer cache did not get update events yet. @kubernetes/sig-storage