When removing a mon from quorum, there is a race condition that
can result in mon quorum going being lost at least temporarily.
The mon pod was being deleted first, and then the mon removed
from quorum. If any other mon went down between the time the
pod of the bad mon was deleted and when the mon was removed from
quorum, there may not be sufficient quorum to complete the
action of removing the mon from quorum and the operator would
be stuck.
For example, there could be 4 mons temporarily due to timing
of upgrading K8s nodes where mons may be taken down for some
number of minutes. Say a new mon is started while the down
mon also comes back up. Now the operator sees it can remove
the 4th mon from quorum, so it starts to remove it. Now say
another mon goes down on another node that is being updated
or otherwise drained. Since the 4th mon pod was deleted
and another mon is down, there are only two mons remaining
in quorum, but 3 mons are required in quorum when there
are 4 mons. Therefore, the quorum is stuck until the
third mon comes back up.
The solution is to first remove the extra mon from quorum
before taking down the mon pod.
Signed-off-by: Travis Nielsen <tnielsen@redhat.com>
(cherry picked from commit 8987d26a6d)
Travis Nielsen
09c90655a7