cheng ce26e78902 For any part, only one replica can move in a rebalance ...

With a min_part_hours of zero, it's possible to move more than one
replicas of the same part in a single rebalance.

This change in behavior only effects min_part_hour zero rings, which
are understood to be uncommon in production mostly because of this
very specific and strange behavior of min_part_hour zero rings.

With this change, no matter how small your min_part_hours it will
always require at least N rebalances to move N part-replicas of the
same part.

To supplement the existing persisted _last_part_moves structure to
enforce min_part_hours, this change adds a _part_moved_bitmap that
exists only during the life of the rebalance, to track when rebalance
moves a part in order to prevent another replicas of the same part
from being moved in the same rebalance.

Add authors: Clay Gerrard, clay.gerrard@gmail.com
             Christian Schwede, cschwede@redhat.com

Closes-bug: #1586167

Change-Id: Ia1629abd5ce6e1b3acc2e94f818ed8223eed993a

2016-09-27 15:01:41 +00:00

29 KiB

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