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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7247) Assignment performances decreased by 50% because of regionserver.OpenRegionHandler#tickleOpening
Date Fri, 30 Nov 2012 20:11:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13507621#comment-13507621
] 

stack commented on HBASE-7247:
------------------------------

bq. If one region server is opening a lot of regions, we just need one handler to tickle the
opening. 

This would be a significant change for I'm-not-sure-what-benefit.  The zk transactions are
region level/scoped and their handling is done at this level in open/close exec handlers.
 Making it so RS does tracking and updating state for master to read regards CLOSING/OPENING
would alter a bunch of code.

I'm all for a reexamination of base operations.  Stuff is this way because we would have issues
where an open would stall for whatever reason... Master would intercept the open, take over
the region and give it to someone else to open.  More often than not, we'd just fail again
for same reason on the new location but the odd time the new re-attempt would succeed.

We could give up reattempt and just let everything hinge on whether a region server has a
zk lease or not and let ServerShutdownHandler do it all.  It'd be a pretty radical difference.
 Simplify code but also, in an odd case, it might mean we'd fail recover a region (I don't
have stats on this).

bq. We used to have the 'owernership' issue as Stack mentioned. Now, I think we are fine since
AM should have a consistent view of region states.

This is a similar type of leap-in-the-dark (smile).  I love the notion that AM is now rock
solid.  It may be given the work expended (it certainly is a million times better) but I'd
like us to run w/ the new AM a while in a few productions before making this ruling.

Again, if we could undo the OPENING/CLOSING, etc., stuff would be cleaner/simpler (logs would
be way less noisy)


                
> Assignment performances decreased by 50% because of regionserver.OpenRegionHandler#tickleOpening
> ------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-7247
>                 URL: https://issues.apache.org/jira/browse/HBASE-7247
>             Project: HBase
>          Issue Type: Improvement
>          Components: master, Region Assignment, regionserver
>    Affects Versions: 0.96.0
>            Reporter: nkeywal
>            Assignee: nkeywal
>            Priority: Critical
>
> The regionserver.OpenRegionHandler#tickleOpening updates the region znode as "Do this
so master doesn't timeout this region-in-transition.".
> However, on the usual test, this makes the assignment time of 1500 regions goes from
70s to 100s, that is, we're 50% slower because of this.
> More generally, ZooKeper commits to disk all the data update, and this takes time. Using
it to provide a keep alive seems overkill. At the very list, it could be made asynchronous.
> I'm not sure how necessary these updates are required (I need to go deeper in the internal,
feedback welcome), but it seems very important to optimize this... The trival fix would be
to make this optional.

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