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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1451) Redo master management of state transitions coalescing and keeping transition state over in ZK
Date Sun, 31 May 2009 16:34:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1451?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12714896#action_12714896

stack commented on HBASE-1451:

>From Ryan Rawson up on list:


I think we could stand to redo the entire region assignment - I ran into a
few bugs whereby we want to assign ROOT/META to the 'best' region but it
doesn't check in because it's trapped trying to talk to the down ROOT/META
server (!).  Instead we now assign ROOT/META to the first server to check
in, thus speeding the recovery anyways.

This all is sort of predicated on a non-master push strategy, im not sure
about the complexity of having the master push assignments.

We could also probably have a dedicated thread to process regionserver
shutdowns, I ran into a few issues (fixed with a priority queue and reduced
timeouts) where we couldn't recover META because i had kill -9ed the META
server while a todo was in process.  It would just hang waiting for timeouts
and META to come back, in the mean time the ProcessServerShutdown which
would recover the META was waiting.

There were lots of weird race conditions when the cluster churn starts going
up while ROOT/META is unassigned/down/unavailable. I think I nailed a bunch
of them.

> Redo master management of state transitions coalescing and keeping transition state over
in ZK
> ----------------------------------------------------------------------------------------------
>                 Key: HBASE-1451
>                 URL: https://issues.apache.org/jira/browse/HBASE-1451
>             Project: Hadoop HBase
>          Issue Type: Task
>            Reporter: stack
>            Assignee: Nitay Joffe
> Chatting w/ Nitay trying to figure non-redeploy of -ROOT- and .META., it struck us that
state transition code is distributed all over master and that execution on state change needs
to be coalesced if any chance of a global understanding.  We thought too that general state
better maintained over in zk so states-in-transition ride over change of master, etc.

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