Improve frequent loops when only one of activities is productive #7679
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What type of PR is this?
/kind feature
What this PR does / why we need it:
In a single iteration of the autoscaler, only one of the activities can occur alternately: scaling up or processing ProvisioningRequests. If the activity is productive (scale up attempt was successful or ProvisioningRequest was processed), the next iteration is started immediately. Unfortunately, if there is only successful processing of ProvisioningRequests without scaling up activity (so if there are only unschedulable pods that CA scale up won't help), the autoscaler will be put to sleep unnecessarily. This PR changes the logic slightly to compare not with the start of the last iteration, but with the previous to the last, to support alternate activities well.
For example, before this PR:
successful provreq processing -> immediate next loop (because provreq was processed) -> scale up attempt with non-successful result -> sleep for scanInterval duration (because scale up attempt was not successful)-> next provreq processing
After:
successful provreq processing -> immediate next loop (because provreq was processed) -> scale up attempt with non-successful result -> immediate next loop (because before the scale up attempt provreq was processed)-> next provreq processing
Which issue(s) this PR fixes:
Fixes #
Special notes for your reviewer:
Does this PR introduce a user-facing change?
Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.: