[kudu-CR] [master] KUDU-3390 support auto rebalance tablet leaders across TServers

["Yingchun Lai (Code Review)" <ge...@cloudera.org>]

Yingchun Lai has posted comments on this change. ( http://gerrit.cloudera.org:8080/18454 )

Change subject: [master] KUDU-3390 support auto rebalance tablet leaders across TServers
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Patch Set 29:

(10 comments)

http://gerrit.cloudera.org:8080/#/c/18454/19//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/18454/19//COMMIT_MSG@10
PS19, Line 10: which lead to load skew on some nodes.
> I take some time to find an issue about leader imbalance at our internal JI
Agree, I also saw many cases that the leader imbalanced and it lead to write and scan (especially when use LEADER_ONLY) performance degraded.


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.h
File src/kudu/master/auto_leader_rebalancer.h:

http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.h@59
PS29, Line 59: Initializes the auto-leader-rebalancer.
nit: how about?
Initializes the objects and starts the thread.

or remove it?


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc
File src/kudu/master/auto_leader_rebalancer.cc:

http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc@68
PS29, Line 68: DEFINE_uint32(auto_leader_rebalancing_rpc_timeout_seconds, 10,
Add some tags for these new added flags, consider ‘experimental’, 'unsafe', 'runtime'.


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc@114
PS29, Line 114:   CHECK(replication_factor > 0);
nit: DCHECK_GT(replication_factor, 0);


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc@120
PS29, Line 120: tablet_id of leader -> uuid
nit: tablet_id -> leader tserver uuid ?


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc@121
PS29, Line 121: leader_uuid_map
In Kudu's naming habit, the map offen named as 'value_by_key', for example  leader_ts_uuid_by_tablet_id.


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc@122
PS29, Line 122: tablet_id of follower -> vector<uuid>
nit: tablet_id -> follower tserver uuids ?


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc@124
PS29, Line 124: tserver uuid -> vector<all leaders' tablet id>
              : 
nit: tserver uuid -> leader replicas ?


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_leader_rebalancer.cc@126
PS29, Line 126: tserver uuid -> vector<all replicas' tablet id>
nit: tserver uuid -> all replicas ?


http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_rebalancer.cc
File src/kudu/master/auto_rebalancer.cc:

http://gerrit.cloudera.org:8080/#/c/18454/29/src/kudu/master/auto_rebalancer.cc@179
PS29, Line 179: 
nit: revert it



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Ibfb60d8759a93b6a19238637c27df4f6b1cac918
Gerrit-Change-Number: 18454
Gerrit-PatchSet: 29
Gerrit-Owner: Yuqi Du <sh...@gmail.com>
Gerrit-Reviewer: Abhishek Chennaka <ac...@cloudera.com>
Gerrit-Reviewer: Alexey Serbin <al...@apache.org>
Gerrit-Reviewer: Andrew Wong <an...@g.ucla.edu>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Reviewer: Yifan Zhang <ch...@163.com>
Gerrit-Reviewer: Yingchun Lai <ac...@gmail.com>
Gerrit-Reviewer: Yuqi Du <sh...@gmail.com>
Gerrit-Comment-Date: Sat, 24 Sep 2022 17:07:19 +0000
Gerrit-HasComments: Yes