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From Jonathan Gray <jg...@facebook.com>
Subject RE: ycsb test on hbase
Date Fri, 10 Sep 2010 20:35:16 GMT
Prioritized compactions and multi-threaded compactions are being addressed with the move to
the ExecutorService/EventHandler way of doing things.

Unfortunately stabilizing the new master (and fixing up brokenness in old master) has taken
priority over that task.

I would say there's a 50% chance that stuff gets in to 0.90 and a 90% chance it is done by
the end of October.

Part of the issue is that we need to fix other stuff at the same time like the issues addressed
in HBASE-2375.  It's feasible to just add prioritization to compactions and I'm going to race
to implement that in late September if I don't have time to address the larger issues at hand.

If anyone wants to work with me on this stuff and has time over the next few weeks, let me
know and we can work together on it.

JG

> -----Original Message-----
> From: Jinsong Hu [mailto:jinsong_hu@hotmail.com]
> Sent: Friday, September 10, 2010 10:50 AM
> To: user@hbase.apache.org
> Subject: Re: ycsb test on hbase
> 
> When I did the test, I found the CPU went to 100% for the compaction
> thread.
> while other cores in the
> OS is not fully utilized. I checked the hbase code and found there is
> only
> one single thread that does
> compaction. That needs to be changed. I found that 0.21 version of
> hbase
> does have this plan to
> use multiple thread to do so, but it appears it will take a long time
> for us
> to get there.
> 
> Another issue that I found with hbase is that when the number of region
> reaches around 1000 for each
> regionserver, the regionserver begin to shutdown by itself for various
> reasons. most of the time
> IO issue with data node. occasionally session expiration issue with
> zookeeper.  This is true regardless
> of what key I use for the table.
> 
> Jimmy.
> 
> --------------------------------------------------
> From: "Jeff Whiting" <jeffw@qualtrics.com>
> Sent: Friday, September 10, 2010 9:44 AM
> To: <user@hbase.apache.org>
> Subject: Re: ycsb test on hbase
> 
> >  We were having the exact same problem when we were doing our own
> load
> > testing with hbase.  We found that a memstore would reach its
> > hbase.hstore.blockingStoreFiles limit or its
> > hbase.hregion.memstore.block.multiplier.  Hitting either of those
> limits
> > prevents writes to the specific region and the client would have to
> pause
> > until a compaction could come through and clean stuff up.
> >
> > However the biggest problem is that there would be a descent size
> > compaction queue, we'd hit one of those limits, and then get put on
> the
> > *back* of the queue and would have to wait *minutes* before it
> finally got
> > to do the compaction we needed to stop the blocking. I created a jira
> to
> > address the issue HBASE-2646.  There is a patch in the jira for
> 0.20.4
> > that creates a priority compaction queue that greatly helped our
> problem.
> > In fact we saw little to no pausing after applying the patch.  In the
> > comments of the jira you can see some of the settings we used to
> prevent
> > the problem without the patch.
> >
> > Apparently there is some work going on to do concurrent priority
> > compaction (Jonathan Gray has been working on it) but I haven't seen
> > anything yet in hbase and don't know the time line.  My personal
> opinion
> > is that we should integrate the patch into trunk and use it until the
> more
> > advanced compactions are implemented.
> >
> > ~Jeff
> >
> > On 9/10/2010 2:27 AM, Jeff Hammerbacher wrote:
> >>> We've been brainstorming some ideas to "smooth out" these
> performance
> >>> lapses, so instead of getting a 10 second period of unavailability,
> you
> >>> get
> >>> a 30 second period of slower performance, which is usually
> preferable.
> >>>
> >> Where is this brainstorming taking place? Could we open a JIRA issue
> to
> >> capture the brainstorming in public and searchable fashion?
> >>
> >
> > --
> > Jeff Whiting
> > Qualtrics Senior Software Engineer
> > jeffw@qualtrics.com
> >
> >

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