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From "Jim Kellerman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-55) [hbase] Improve Master region assignment function
Date Tue, 19 Feb 2008 00:08:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-55?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12570058#action_12570058

Jim Kellerman commented on HBASE-55:

Right now the master gives the region server one hbase.hbasemaster.maxregionopen (currently
the same as hbase.master.lease.period) to acknowledge that it received the open request with
a HMsg.MSG_REPORT_PROCESS_OPEN If the master receives that message, it adds an additional
maxregionopen time period for the region server to send a HMsg.MSG_REPORT_OPEN (the region
is now on-line), before the master will reassign the region.

It is possible that it could take longer than that amount of time if there are a lot of log
entries to apply or if the initial compaction on region open takes a while or if we get into
one of those situations in which the region server cannot talk to the master (I'd really like
to find out why this happens).

Currently the region server only reports in once per hbase.master.lease.period. This is probably
too infrequent as we often see both MSG_REPORT_PROCESS_OPEN and MSG_REPORT_OPEN in the same
set of messages.

Probably maxregionopen should be greater than lease.period or we should add a new parameter
"heartbeat.interval" which would be less than the lease period so the region server would
report in more frequently. 

And, if the master receives a MSG_REPORT_PROCESS_OPEN, it should not take any action with
respect to reassigning the region unless the region server's lease times out.

> [hbase] Improve Master region assignment function
> -------------------------------------------------
>                 Key: HBASE-55
>                 URL: https://issues.apache.org/jira/browse/HBASE-55
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: master
>            Reporter: Bryan Duxbury
>             Fix For: 0.2.0
> We would like the master's region assignment function to take into account more factors
when choosing where to assign regions.
> - More advanced accounting of load on regionserver - memory, # requests, etc
> - Don't deploy both daughter regions to the same regionserver
> - Assign regions where the underlying DFS blocks are hosted if possible
> Please add additional ideas in comments as they come up.

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