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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6841) Meta prefetching is slower than doing multiple meta lookups
Date Fri, 21 Sep 2012 17:00:08 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13460619#comment-13460619
] 

Lars Hofhansl commented on HBASE-6841:
--------------------------------------

Which client did you jstack? There're at least two clients at work here: The one the attempts
the truncate and the ones that still perform the requests.
I assume the stuck ones are the those that are still performing the requests.

I am beginning to doubt that prefetching is a issue here. This has to do with how these clients
connect. There should not need to be a connection setup each time.

                
> 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
>            Assignee: Lars Hofhansl
>            Priority: Critical
>             Fix For: 0.94.2
>
>         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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