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From Jeff Whiting <je...@qualtrics.com>
Subject Re: Slow Get performance, is there a way to profile a Get?
Date Tue, 21 Feb 2012 20:19:06 GMT
We are still on 0.90.x.  Since it is just a development cluster we may upgrade to 0.92.x to
get the 
slow query facility and see if the condition persists in the newer version.  If we don't upgrade

we'll try what you are suggesting and pull the content out and do some stand alone testing
to see if 
we can reproduce the slowness.


On 2/18/2012 11:32 AM, Stack wrote:
> On Fri, Feb 17, 2012 at 2:38 PM, Jeff Whiting<jeffw@qualtrics.com>  wrote:
>> Is there way to profile a specific get request to see where the time is
>> spent (e.g. checking memstore, reading from hdfs, etc)?
> In 0.92, there is a slow query facility that dumps out context when
> queries are>  some configured time.  I presume you are on 0.90.x
>> We are running into a problem where a get after a delete goes really slow.
>>   We have a row that has between 100 to 256 MB of data in it across a couple
>> hundred columns.  After putting the data we can get the data out quickly (<
>> 100ms).  So a get on "info:name" will take ~0.05110 seconds according the
>> hbase shell. We then delete the entire row (e.g. htable.delete(new
>> Delete(rowkey)).  Most of the time after deleting the row trying the exact
>> same get on "info:name" becomes significantly slower (1.9400 to 3.1840
>> seconds).  Putting data back into "info:name" still results in the same slow
>> performance.  I was hoping to profile the get to see where the time is going
>> and seeing what we can do to tune how we are using hbase.
> If you flush the region -- you can do this from the shell -- is it
> still slow?  If so, it means slowness is from accessing hfiles.  Try
> copying the region content out and rig up a little harness to bring
> the region in a context free from the running cluser.  See TestHRegion
> for sample code on how to stand up a HRegion instance.
> St.Ack

Jeff Whiting
Qualtrics Senior Software Engineer

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