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From "Charlie Qiangeng Xu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-17110) Add an "Overall Strategy" option(balanced both on table level and server level) to SimpleLoadBalancer
Date Wed, 16 Nov 2016 08:48:58 GMT
Charlie Qiangeng Xu created HBASE-17110:
-------------------------------------------

             Summary: Add an "Overall Strategy" option(balanced both on table level and server
level) to SimpleLoadBalancer
                 Key: HBASE-17110
                 URL: https://issues.apache.org/jira/browse/HBASE-17110
             Project: HBase
          Issue Type: New Feature
          Components: Balancer
    Affects Versions: 1.2.4, 2.0.0
            Reporter: Charlie Qiangeng Xu
            Assignee: Charlie Qiangeng Xu


This jira is about an enhancement of simpleLoadBalancer. Here we introduce a new strategy:
"bytableOverall" which could be controlled by adding:
<property>
  <name>hbase.master.loadbalance.bytableOverall</name>
  <value>true</value>
</property>
We have been using the strategy on our largest cluster for several months. it's proven to
be very helpful and stable, especially, the result is quite visible to the users.

Here is the reason why it's helpful:
When operating large scale clusters(our case), some companies still prefer to use SimpleLoadBalancer
due to its simplicity, quick balance plan generation, etc. Current SimpleLoadBalancer has
two mode: 
1. byTable, which only guarantees that the regions of one table could be uniformly distributed.

2. byCluster, which ignores the distribution within tables and balance the regions all together.
If the pressures on different tables are different, the first byTable option is preferable
one in most case. Yet, this choice sacrifice the cluster level balance and would cause some
servers to have significantly higher load, e.g. 240 regions on server A but 410 regions on
server B.
Consider this case,  a cluster has 3 tables and 4 servers:
  server A has 3 regions: table1:1, table2:1, table3:1
  server B has 3 regions: table1:2, table2:2, table3:2
  server C has 3 regions: table1:3, table2:3, table3:3
  server D has 0 regions.
>From the byTable strategy's perspective, the cluster has already been perfectly balanced
on table level. But a perfect status should be like:
  server A has 2 regions: table2:1, table3:1
  server B has 2 regions: table1:2, table3:2
  server C has 3 regions: table1:3, table2:3, table3:3
  server D has 2 regions: table1:1, table2:2
And this is what the new mode "byTableOverall" can achieve.

Two UTs have been added as well and the last one demonstrates the advantage of the new strategy.




 



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