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

Change subject: [master] KUDU-3061 support auto rebalance tablet leaders across 
TServers
......................................................................


Patch Set 21:

(2 comments)

Thanks your crs.

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.
> Do you have any data to show how much imbalance it is?  I'm not convinced t
I take some time to find an issue about leader imbalance at our internal JIRA 
before.

The issue is about user query kudu failed because of timeout. Because the 
cluster only 3 tservers so the replica is balanced.

We can see leader imbalance, All tables' leader distribution:
kudu cluster ksck $master_list -ksck_format=plain_full | grep LEADER | awk 
'{print$2}' | sort | uniq -c
60 (YYY-prod1.ZZZ.XXX.cloud:7050):
4 (tYYY-prod2.ZZZ.XXX.cloud:7050):
113 (YYY-prod3.ZZZ.XXX.cloud:7050):

node prod2 only 4 leaders and node prod3 has 113 leaders, the good distribution 
is (59, 59, 59) or so.


The table event_wos_p2_correction's leader distribution:
kudu cluster ksck $master_list -ksck_format=plain_full 
--tables=event_wos_p2_correction | grep LEADER | awk '{print$2}' | sort | uniq 
-c
6 (YYY-prod1.ZZZ.XXX.cloud:7050):
12 (YYY-prod3.ZZZ.XXX.cloud:7050):

We can see node2 has no leader, the good distribution is (6, 6, 6) or so.


http://gerrit.cloudera.org:8080/#/c/18454/19//COMMIT_MSG@21
PS19, Line 21: maybe cause imbalanced load
> Yes, I understand it's not easy to setup a proper measurement experiment an
OK, I have found a history issue and reply an above cr, but cpu usage and 
memory cann't find.
After a few days, I can make a workload to test some data about cpu and memory 
usage.



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Ibfb60d8759a93b6a19238637c27df4f6b1cac918
Gerrit-Change-Number: 18454
Gerrit-PatchSet: 21
Gerrit-Owner: Yuqi Du <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Reviewer: Yifan Zhang <[email protected]>
Gerrit-Reviewer: Yingchun Lai <[email protected]>
Gerrit-Reviewer: Yuqi Du <[email protected]>
Gerrit-Comment-Date: Tue, 26 Jul 2022 04:25:05 +0000
Gerrit-HasComments: Yes

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