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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 Wed, 05 Dec 2012 19:35:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13510712#comment-13510712
] 

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

bq. Implicitly, it means we still have a race condition here, just that the probability is
quite low.

Yeah.  By-product of our keeping state across multiple systems (up in zk and then some state
in .meta.).  We could change this to a checkAndPut.  Read .META. at start of the opening or
have master pass over the .META. timestamp or something key to .META. and we'd use it doing
checkAndSet into .META. table... would be more strict than this updating zk.

bq. It would be a huge simplification imho. It's worth trying, I would say. It actually makes
sense to do it now, because once the current trunk code will be production proven, touching
it will be scarier.

I'd go along.  We should discuss out on dev first.  I have short-term memory.  I'm currently
of the opinion that this expensive facility of master failing an open because it has been
taking too long on a particular regionserver has been of no use -- worse, it has only caused
headache -- but I may be just not remembering and others out on dev list will have better
recall than I.


                
> 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
>             Fix For: 0.96.0
>
>         Attachments: 7247.v1.patch
>
>
> 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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