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Posted to dev@hbase.apache.org by "Evgeny Ryabitskiy (JIRA)" <ji...@apache.org> on 2009/03/10 03:08:50 UTC
[jira] Assigned: (HBASE-1017) Region balancing does not bring newly added node within acceptable range

     [ https://issues.apache.org/jira/browse/HBASE-1017?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Evgeny Ryabitskiy reassigned HBASE-1017:
----------------------------------------

    Assignee: Evgeny Ryabitskiy

> 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
>
>
> 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,^@^@^@^@^AHï¿½;,1225411051632
> 2008-11-21 15:57:53,351 DEBUG org.apache.hadoop.hbase.master.RegionManager: Going to close region streamitems,^@^@^@^@^@ï¿½Ý,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^Zï¿½,1225411056701
> 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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