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HBase >> mail # user >> Many scanner opening

Eugeny Morozov 2012-12-18, 08:01
lars hofhansl 2012-12-19, 02:23
Eugeny Morozov 2012-12-20, 10:32
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Re: Many scanner opening

You probably made it less likely that your scanners will scan the same HFile in parallel.

-- Lars

 From: Eugeny Morozov <[EMAIL PROTECTED]>
Sent: Thursday, December 20, 2012 2:32 AM
Subject: Re: Many scanner opening

Cool stuff! Thanks a lot! I'm not sure I can apply the patch, cause we're
using CDH-4.1.1, but increasing size of internal scanner does the trick -
decreased number of scanners.
At least temporarily it's good enough.


On Wed, Dec 19, 2012 at 6:23 AM, lars hofhansl <[EMAIL PROTECTED]> wrote:

> You might have run into HBASE-7336.
> (Not available in any official release, yet)
> If you're using 0.94 (and probably 0.92) you can just apply this patch
> (it's save and simple).
> ________________________________
>  From: Eugeny Morozov <[EMAIL PROTECTED]>
> Sent: Tuesday, December 18, 2012 12:01 AM
> Subject: Many scanner opening
> Hello!
> We faced an issue recently that the more map tasks are completed, the
> longer it takes to complete one more map task.
> In our architecture we have two scanners to read the table. The first one,
> which is called 'outer' scanner is reading table and filter some rowkeys.
> These rowkeys are used as a filter for second scanner - 'internal'. Thus we
> constantly open 'internal' scanner with different filters.
> As an additional symptoms we see that our cluster practically does nothing
> - there is no CPU loading, no disk loading, no network, etc. Most of the
> time it means we are waiting on some locks, but I'm not sure.
> I would appreciate any ideas or suggestions to understand the case.
> Thank you in advance.
> --
> Evgeny Morozov
> Developer Grid Dynamics
> Skype: morozov.evgeny
> www.griddynamics.com

Evgeny Morozov
Developer Grid Dynamics
Skype: morozov.evgeny
Eugeny Morozov 2012-12-23, 18:32
Michael Segel 2012-12-20, 13:14