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From "Miro Walker" <miro.wal...@cognifide.com>
Subject RE: possible performance problem (need a way to test it)
Date Mon, 18 Sep 2006 15:48:15 GMT
Hi Alex,

I think the investigation is a good idea, but the way we sidestepped any
issues like this was to have our application maintain a pool of sessions
that are shared out between user threads. This works for us as we are
handling user locking and security in the application tier - I guess it
depends on your overall architecture, but it might be worth considering
if you're planning very high concurrency.

miro

-----Original Message-----
From: Alexandru Popescu [mailto:the.mindstorm.mailinglist@gmail.com] 
Sent: 18 September 2006 16:18
To: userJackrabbit
Subject: possible performance problem (need a way to test it)

Hi!

I have identified a possible performance problem with high concurrency
querying against JCR. Still, I would like to have an easy way to
reproduce it, so that I can profile it. I am wondering if there are in
the Jackrabbit source base good samples on how to set up a quick
testing repository.

This was the first part. Now about the real problem I am seeing: when
accessing the JCR repo from multiple concurrent threads (each using
its own Session) and we perform querying we see a huge CPU load and
the response times are growing very fast:
- for 5 concurrent threads the query reponse times are around 200-500
ms; server load about 0.65-0.7
- for 100 concurrent threads the query response times are around
150000-200000 ms; server load about 7-7.5

As you can see these are very dangerous numbers, and I would
definitely like to figure out what is the problem behind them, because
in my application I can expect something around 300 concurrent threads
access.

I know I can start looking at different options like caching and
similar ideas, but firstly understanding the real problem will help me
a lot.

Many thanks for any helping ideas and comments,

./alex
--
:Architect of InfoQ.com:
 .w( the_mindstorm )p.
Co-founder of InfoQ.com

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