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From "Alexandru Popescu" <the.mindstorm.mailingl...@gmail.com>
Subject Working with JCR in highly concurrent applications
Date Wed, 20 Sep 2006 09:45:07 GMT
Hi everybody!

First of all I must say that I do not intend to create noise about
this, but unfortunately it looks like I have reached a dead end.
Hopefully there is something I am doing wrong, or that I am supposed
to do differently. I haven't found any best practices or
recommendations anywhere, so this is a try-and-fail process (and I am
saying it is a "fail" because till now I haven't figured out the
correct way to do it).

Scenario: access a set of nodes (matching more or less complex
filtering criteria) from a highly concurrent application.

As you can see this is a pretty straight forward scenario.

I have tried 2 different approaches and unfortunately both are
degrading when used in this concurrent environment. And I am not
talking about a few hundred concurrent threads: I have tested it with
50, respectively 100 concurrent threads.

The common usage scenario is having a JCR Session per thread association.

Usage scenario 1:  Query API.

As posted in a previous email this is degrading very fast. See email:
"possible performance problem (need a way to test it)" from Sept 19th.

Usage scenario 2: Normal navigation API

The second approach was to manually navigate the parent child nodes,
read just a couple of properties in the first place so that I do
manually the filtering, and only afterwards fetch the entire node
properties.

Once again, the performance is going down 2-3 order of magnitude (from
hundreds of ms down to ten thousands (even hundred thousand) ms).

I have profiled the 2nd test and at the first glance the most
expensive operations are the following calls:

ItemManager.createItemInstance
ItemManager.retrieveItem

These calls are always invoked from Node.getProperty,
Node.hasProperty, etc., so I don't think I am doing something wrong.

I am extremely worried about these results because I don't see a way
to achieve my scenario without involving more advance techniques. I
agree that if my application needs good performance these techniques
will need to be used, but I find it very concerning the fact that
performance is degrading so fast by its own.

I would be happy to hear any comments, any suggestions, any pointers
to what I am doing wrongly, that will lead me to a good solution.

Many thanks in advance,

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

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