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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HBASE-1737) Regions unbalanced when adding new node
Date Mon, 03 Aug 2009 21:42:14 GMT

     [ https://issues.apache.org/jira/browse/HBASE-1737?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Jonathan Gray updated HBASE-1737:

    Attachment: HBASE-1737-v1.patch

Fixes small bug in RegionManager.

When looking at the most loaded server, we check to see if there is another server that is
underloaded.  When we determine we should unassign from it (numRegionsToClose = 0) then we
determine how many to unassign.  However, we don't re-set numRegionsToClose to the number
determine for reassignment (so it stays at 0, and thus 0 are reassigned).

Also has a few small formatting changes and an extra variable in log line.

> Regions unbalanced when adding new node
> ---------------------------------------
>                 Key: HBASE-1737
>                 URL: https://issues.apache.org/jira/browse/HBASE-1737
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.20.0
>            Reporter: Jonathan Gray
>            Priority: Blocker
>             Fix For: 0.20.0
>         Attachments: HBASE-1737-v1.patch
> When adding a new RegionServer to a cluster, the new RS will receive some regions but
not enough to actually be considered balanced.
> To recreate, just take an RS offline, allow regions to be reassigned, and then bring
it back up.
> Master will get itself into a broken, stuck state where it continuously outputs a line
like this:
> {noformat}
> 2009-08-03 12:54:57,812 DEBUG org.apache.hadoop.hbase.master.RegionManager: Server dn4,60020,1249329081079
will be unloaded for balance. Server load: 341 avg: 318.0, regions can be moved: 55
> {noformat}
> This line is output every 3 seconds and never stops until another RS joins/leaves the
> Making this a blocker because when your new RS only gets some regions (in my case, about
half as many as it should have), then all new regions will be assigned to that RS.  This basically
destroys any possibility for good load distribution with new data.

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