[jira] [Commented] (HBASE-6841) Meta prefetching is slower than doing multiple meta lookups

["Amitanand Aiyer (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-6841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609585#comment-13609585 ] 

Amitanand Aiyer commented on HBASE-6841:
----------------------------------------

I have seen some issues recently when there are large failures in our cluster. 

Looking at the jstacks taken during the failures, It looks like all client threads are blocking on the synchronized (regionLockObject) call,
in locateRegionInMeta.

Seems like the threads go in and do the cache warmup; although the cache might have been already warmed up by an earlier thread. 
                
> Meta prefetching is slower than doing multiple meta lookups
> -----------------------------------------------------------
>
>                 Key: HBASE-6841
>                 URL: https://issues.apache.org/jira/browse/HBASE-6841
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Jean-Daniel Cryans
>         Attachments: 6841-0.94.txt, 6841-0.96.txt
>
>
> I got myself into a situation where I needed to truncate a massive table while it was getting hits and surprisingly the clients were not recovering. What I see in the logs is that every time we prefetch .META. we setup a new HConnection because we close it on the way out. It's awfully slow.
> We should just turn it off or make it useful. jstacks coming up.

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