Backport of docs: clarify reschedule, migrate, and replacement terminology into release/1.9.x #25145
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Backport
This PR is auto-generated from #24929 to be assessed for backporting due to the inclusion of the label backport/1.9.x.
The below text is copied from the body of the original PR.
Our vocabulary around scheduler behaviors outside of the
rescheduleandmigrateblocks leaves room for confusion around whether the reschedule tracker should be propagated between allocations. There are effectively five different behaviors we need to cover:restart: when the tasks of an allocation fail and we try to restart the tasks in place.
reschedule: when the
restartblock runs out of attempts (or the allocation fails before tasks even start), and we need to move the allocation to another node to try again.migrate: when the user has asked to drain a node and we need to move the allocations. These are not failures, so we don't want to propagate the reschedule tracker.
replacement: when a node is lost, we don't count that against the
rescheduletracker for the allocations on the node (it's not the allocation's "fault", after all). We don't want to run themigratemachinery here here either, as we can't contact the down node. To the scheduler, this is effectively the same as if we bumped thegroup.countreplacement for
disconnect.replace = true: this is a replacement, but the replacement is intended to be temporary, so we propagate the reschedule tracker.Add a section to the
reschedule,migrate, anddisconnectblocks explaining when each item applies. Update the use of the word "reschedule" in several places where "replacement" is correct, and vice-versa.Fixes: #24918
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