Alexey Serbin has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/14222 )

Change subject: KUDU-2069 p4: stop replication from failed servers in 
maintenance mode
......................................................................


Patch Set 2:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/14222/2/src/kudu/consensus/quorum_util.cc
File src/kudu/consensus/quorum_util.cc:

http://gerrit.cloudera.org:8080/#/c/14222/2/src/kudu/consensus/quorum_util.cc@456
PS2, Line 456: peer.attrs().replace()
> I should have been more clear on what I said.
Ah, just another observation.  Probably, I should have mentioned that earlier 
for clarity.

If I'm not mistaken, only tools like 'cluster rebalancer' and 'tablet 
change_config move_replica' set the 'REPLACE' attribute to make replica to be 
moved to some other tablet server.  That corresponds to ChangeConfigType of 
MODIFY_PEER.  The automatic re-replication in master uses ADD_PEER and 
REMOVE_PEER correspondingly.

So, if we are about to ignore the REPLACE attribute when a tablet server is in 
the maintenance mode, that means a running session of the rebalancer tool of an 
explicit replica movement would stuck until the source tablet server is back 
into the regular (non-maintenance mode).

Maybe it's worth double-checking what we want from the operability perspective 
here if ignoring the REPLACE attribute for tablet servers went into the 
maintenance mode:
 * allow for accumulation of those 'REPLACE' attributes set for replicas hosted 
by a tablet server in the maintenance mode (and be prepared for corresponding 
movements once the server is back into the normal mode)
 * explicitly disallow setting the 'REPLACE' attribute for replicas hosted by a 
tablet server in the maintenance mode

Another alternative would be honoring the 'REPLACE' attribute even if a tablet 
server is in the maintenance mode, given that the presence of the 'REPLACE' 
attribute means it has been set explicitly, and it was not a result of the 
automatic re-replication activity.



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I9a63b55011d16900c0d27eac0eb75880074204db
Gerrit-Change-Number: 14222
Gerrit-PatchSet: 2
Gerrit-Owner: Andrew Wong <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Hao Hao <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Comment-Date: Tue, 17 Sep 2019 00:38:48 +0000
Gerrit-HasComments: Yes

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