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Accumulo >> mail # user >> RE: EXTERNAL: Re: Failing Tablet Servers


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Cardon, Tejay E 2012-09-20, 21:26
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Jim Klucar 2012-09-20, 22:44
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Cardon, Tejay E 2012-09-20, 22:50
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Jim Klucar 2012-09-20, 22:56
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Adam Fuchs 2012-09-20, 23:21
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Cardon, Tejay E 2012-09-21, 14:12
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Re: EXTERNAL: Re: Failing Tablet Servers
memory.maps is what defines the size of the in memory map. When using
native maps, that space does not come out of the heap size. But when using
non-native maps, it comes out of the heap space.

I think the issue Eric is trying to hit at is the fickleness of the java
garbage collector. When you give a process that much heap, that's so much
more data you can hold before you need to garbage collect. However, that
also means when it does garbage collect, it's collecting a LOT more, which
can result is poor performance.

John

On Fri, Sep 21, 2012 at 10:12 AM, Cardon, Tejay E
<[EMAIL PROTECTED]>wrote:

>  Jim, Eric, and Adam,****
>
> Thanks.  It sounds like you’re all saying the same thing.  Originally I
> was doing each key/value as its own mutation, and it was blowing up much
> faster (probably due to the volume/overhead of the mutation objects
> themselves.  I’ll try refactoring to break them up into something
> in-between.  My keys are small (<25 Bytes), and my values are empty, but
> I’ll aim for ~1,000 key/values per mutation and see how that works out for
> me.****
>
> ** **
>
> Eric,****
>
> I was under the impression that the memory.maps setting was not very
> important when using native maps.  Apparently I’m mistaken there.  What
> does this setting control when in a native map setting?  And, in general,
> what’s the proper balance between tserver_opts and tserver.memory.maps?***
> *
>
> ** **
>
> With regards to the “Finished gathering information from 24 servers in
> 27.45 seconds”  Do you have any recommendations for how to chase down the
> bottleneck?  I’m pretty sure I’m having GC issues, but I’m not sure what is
> causing them on the server side.  I’m sending a fairly small number of very
> large mutation objects, which I’d expect to be a moderate problem for the
> GC, but not a huge one..****
>
> ** **
>
> Thanks again to everyone for being so responsive and helpful.****
>
> ** **
>
> Tejay Cardon****
>
> ** **
>
> ** **
>
> *From:* Eric Newton [mailto:[EMAIL PROTECTED]]
> *Sent:* Friday, September 21, 2012 8:03 AM
>
> *To:* [EMAIL PROTECTED]
> *Subject:* EXTERNAL: Re: Failing Tablet Servers****
>
>  ** **
>
> A few items noted from your logs:****
>
> ** **
>
> tserver.memory.maps.max = 1G****
>
>  ** **
>
> If you are giving your processes 10G, you might want to make the map
> larger, say 6G, and then reduce the JVM by 6G.****
>
> ** **
>
> Write-Ahead Log recovery complete for rz<;zw== (8 mutations applied,
> 8000000 entries created)****
>
>  ** **
>
> You are creating rows with 1M columns.  This is ok, but you might want to
> write them out more incrementally.****
>
> ** **
>
> WARN : Running low on memory****
>
>  ** **
>
> That's pretty self-explanatory.  I'm guessing that the very large
> mutations are causing the tablet servers to run out of memory before they
> are held waiting for minor compactions.****
>
> ** **
>
> Finished gathering information from 24 servers in 27.45 seconds****
>
>  ** **
>
> Something is running slow, probably due to GC thrashing.****
>
> ** **
>
> WARN : Lost servers [10.1.24.69:9997[139d46130344b98]]****
>
>  ** **
>
> And there's a server crashing, probably due to an OOM condition.****
>
> ** **
>
> Send smaller mutations.  Maybe keep it to 200K column updates.  You can
> still have 1M wide rows, just send 5 mutations.****
>
> ** **
>
> -Eric****
>
> ** **
>
> On Thu, Sep 20, 2012 at 5:05 PM, Cardon, Tejay E <[EMAIL PROTECTED]>
> wrote:****
>
> I’m seeing some strange behavior on a moderate (30 node) cluster.  I’ve
> got 27 tablet servers on large dell servers with 30GB of memory each.  I’ve
> set the TServer_OPTS to give them each 10G of memory.  I’m running an
> ingest process that uses AccumuloInputFormat in a MapReduce job to write
> 1,000 rows with each row containing ~1,000,000 columns in 160,000
> families.  The MapReduce initially runs quite quickly and I can see the
> ingest rate peak on the  monitor page.  However, after about 30 seconds of
> high ingest, the ingest falls to 0.  It then stalls out and my map task are
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Cardon, Tejay E 2012-09-21, 14:35
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Jim Klucar 2012-09-21, 14:40
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Eric Newton 2012-09-21, 14:32
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Cardon, Tejay E 2012-09-21, 14:50