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https://issues.apache.org/jira/browse/HBASE-1017?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Evgeny Ryabitskiy updated HBASE-1017:
-------------------------------------
Attachment: hbase1017_v3.patch
Extract balancing to LoadBalancer class + more re-factoring + sync wit SVN
> Region balancing does not bring newly added node within acceptable range
> ------------------------------------------------------------------------
>
> Key: HBASE-1017
> URL: https://issues.apache.org/jira/browse/HBASE-1017
> Project: Hadoop HBase
> Issue Type: Improvement
> Affects Versions: 0.19.0
> Reporter: Jonathan Gray
> Assignee: Evgeny Ryabitskiy
> Priority: Minor
> Fix For: 0.20.0
>
> Attachments: HBASE-1017_v1.patch, HBASE-1017_v2.patch,
> hbase1017_v3.patch
>
>
> With a 10 node cluster, there were only 9 online nodes. With about 215 total
> regions, each of the 9 had around 24 regions (average load is 24). Slop is
> 10% so 22 to 26 is the acceptable range.
> Starting up the 10th node, master log showed:
> {code}
> 2008-11-21 15:57:51,521 INFO org.apache.hadoop.hbase.master.ServerManager:
> Received start message from: 72.34.249.210:60020
> 2008-11-21 15:57:53,351 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Server 72.34.249.219:60020 is overloaded. Server load: 25 avg: 22.0, slop: 0.1
> 2008-11-21 15:57:53,351 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Choosing to reassign 3 regions. mostLoadedRegions has 10 regions in it.
> 2008-11-21 15:57:53,351 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Going to close region streamitems,^...@^@^...@^@^AH�;,1225411051632
> 2008-11-21 15:57:53,351 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Going to close region streamitems,^...@^@^...@^@^...@�Ý,1225411056686
> 2008-11-21 15:57:53,351 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Going to close region groups,,1222913580957
> 2008-11-21 15:57:53,975 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Server 72.34.249.213:60020 is overloaded. Server load: 25 avg: 22.0, slop: 0.1
> 2008-11-21 15:57:53,975 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Choosing to reassign 3 regions. mostLoadedRegions has 10 regions in it.
> 2008-11-21 15:57:53,976 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Going to close region upgrade,,1226892014784
> 2008-11-21 15:57:53,976 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Going to close region streamitems,^...@^@^...@^@^...@3^z�,1225411056701
> 2008-11-21 15:57:53,976 DEBUG org.apache.hadoop.hbase.master.RegionManager:
> Going to close region streamitems,^...@^@^...@^@^@ ^L,1225411049042
> {code}
> The new regionserver received only 6 regions. This happened because when the
> 10th came in, average load dropped to 22. This caused two servers with 25
> regions (acceptable when avg was 24 but not now) to reassign 3 of their
> regions each to bring them back down to the average. Unfortunately all other
> regions remained within the 10% slop (20 to 24) so they were not overloaded
> and thus did not reassign off any regions. It was only chance that made even
> 6 of the regions get reassigned as there could have been exactly 24 on each
> server, in which case none would have been assigned to the new node.
> This will behave worse on larger clusters when adding a new node has little
> impact on the avg load/server.
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