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From Mike Kienenberger <>
Subject Re: Memory Management using Tomcat
Date Wed, 16 Sep 2009 19:10:37 GMT
1.)  128 still seems small to me.   I don't think I run anything at
less than 256.
On the other hand, We have an app with 1000s of customers that uses
512Mb, I think.   So 1500 seems excessive.

2.)  BaseContext.getThreadObjectContext() just tells how you're
getting a context.  It doesn't tell how it's managed.   Do you have a
servlet filter that creates a new ObjectContext at the start of a
request and then clears it out at the end?   Or does it do this per
session?   I've never looked at the method, but it might default to
creating one permanent data context per thread if you don't do
anything else (like set up a servlet filter).   That could be part of
the problem.

On Wed, Sep 16, 2009 at 2:49 PM, Joe Baldwin <> wrote:
> Caveat: Apparently I am not as well. :)
> 1.) I looked at the 65M issue.  On my development box (OSX) I set it to
> -Xms128m -Xmx128m (basically arbitrary).  So when I went to the remote
> hosting company, I purchase a similar amount.
>        a. However, we are doing *very* little work (lots of product fetches
> and only a few product inserts and updates) and it runs out of memory *very*
> fast which I *assume* means it is my code, but I don't know.
>        b. I am doing research and here is a "web recommendation" (for all
> that is worth)
>                Whenever possible, Unidata recommends
>        -Xmx1500m for 32-bit systems, and -Xmx2048m --Xmx4096m for 64-bit
> systems.
>        c. Since the host is 64-bit, I am wondering whether my assumptions
> may be off for 64-bit systems.
> 2. DataContext: Sorry, but I am getting confused on this one.  I am using
> BaseContext.getThreadObjectContext() based on recommendations (I converted
> all the old DataContext refs to BaseContext, but I don't really understand
> it from reading the docs) and am *not* releasing it at the end of session.
>  Not quite sure of how to do this properly.
> 3. Don't know how to set the cache to retain N number of objects. I
> experimented with
>        query.setPageSize(RowsPerPage);
>        query.setCacheStrategy(QueryCacheStrategy.SHARED_CACHE);
>        query.setCacheGroups("product", "ProductList");
> This seemed to help quite a bit but I still eventually ran out of memory.  I
> recently removed *all* the SHARED_CACHE and it ran out of memory very fast.
> Thanks for your input
> Joe
> On Sep 16, 2009, at 2:25 PM, Mike Kienenberger wrote:
>> Caveat: I'm not really an expert on Cayenne memory management.
>> 1) Are you allocating enough heap memory to the app server to start
>> with?   I don't know what the default is these days, but in the old
>> days, an application by default only gets 64Mb of memory -- that's
>> pretty small.
>> 2) Are you using a new DataContext per request?  Or at least per session?
>> 3) I seem to remember that the cache strategy is configurable.  Have
>> you configured a cache that only retains N number of objects for a
>> suitable value of N?
>> On Wed, Sep 16, 2009 at 2:11 PM, Joe Baldwin <>
>> wrote:
>>> Hi,
>>> I have asked this question a number of ways but I still have a very
>>> serious
>>> problem with Cayenne-specific memory management configuration associated
>>> with Tomcat.
>>> The problem with debugging is that given that I have very little
>>> visibility
>>> into the Cayenne memory management it is extremely difficult to debug
>>> this
>>> using conventional strategies.  Also I am not requesting anything from
>>> the
>>> system that is terribly exceptional so I am attempting to use default
>>> settings as much as possible.
>>> My strategy is to ask the experts for a Cayenne configuration and
>>> standard
>>> memory management steps I should take to conform to the new Cayenne
>>> memory
>>> management design intentions.
>>> Problem:
>>> 1. I have essentially a webstore, three tier design with Tomcat, Cayenne
>>> and
>>> MySQL.
>>> 2. When after only a few queries of products, tomcat freezes up and
>>> reports
>>> out of memory errors.
>>> I have attempted to configure the caching strategy ask best as I can
>>> understand from the docks but this only gets me a few more hours of usage
>>> before the out of memory errors.  (I tried the SHARED_CACHE). The
>>> strategy is worse.
>>> I would appreciate a set of steps (aka a primer) that should handle a
>>> website with a lot of fetches of hundreds of data objects (i.e. products)
>>> and very few updates.
>>> Note: My gut feeling is that I am not properly managing the data object
>>> array properly and it is leaking memory.
>>> I would appreciate any input, but I would first like to know what the
>>> minimum require steps are for managing at data object result set
>>> ArrayList
>>> so as to properly cache and then properly free the memory after it is no
>>> longer needed.
>>> Context: Tomcat, MySQL, Cayenne 3.0M6
>>> Thanks,
>>> Joe Baldwin

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