Yifan Zhang has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/14154 )

Change subject: KUDU-2914: Rebalance tool support moving replicas from some 
specific tablet servers
......................................................................


Patch Set 2:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/14154/2/src/kudu/tools/rebalancer_tool.cc
File src/kudu/tools/rebalancer_tool.cc:

http://gerrit.cloudera.org:8080/#/c/14154/2/src/kudu/tools/rebalancer_tool.cc@951
PS2, Line 951:   if (!cluster_info.healthy_ignored_tservers.empty()) {
             :     // Check if it is safe to remove ignored tservers from the 
cluster.
             :     int remaining_tservers_count = 
cluster_info.balance.servers_by_total_replica_count.size();
             :     if (remaining_tservers_count < max_replication_factor) {
             :       return Status::InvalidArgument(Substitute(
             :         "Too many ignored tservers.\nThe number of remaining 
tservers must be at least $0.",
             :         max_replication_factor));
             :     }
             :     
RETURN_NOT_OK(algorithm()->MoveReplicasFromTservers(&cluster_info,
             :                                                         
max_moves_per_server_ * 5,
             :                                                         &moves));
             :   }
> To simplify the matters, is it possible to move the replicas from the healt
Moving the replicas from the healthy ignored tservers and moving the replicas 
in the rebalancing progress are almost the same progress, the only difference 
is to get particular movements, so I just added an extra step to get optional 
movements. Maybe I should put those codes in another method and it will looks 
simpler.

I think the algorithm to get those optional movement should be different when 
running in one location and multiple locations, we should select different 
server in order to move fewer replicas in the next rebalancing progress. And 
the idea to get those optional movement is consistent with the existing 
algorithms. Compared with introducing another two algorithms, maybe 
implementing new features in the existing ones will be simpler.



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I86cfb740030946c13db1a9ca63d241f4907d6c89
Gerrit-Change-Number: 14154
Gerrit-PatchSet: 2
Gerrit-Owner: Yifan Zhang <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Yifan Zhang <[email protected]>
Gerrit-Comment-Date: Fri, 06 Sep 2019 12:51:11 +0000
Gerrit-HasComments: Yes

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