Mike,
thanks for your ideas. I am still a bit mystified by the rules concerning
garbage collection I worked on a a project some time back on this and became
very adept at managing memory. However, when I have advanced software like
Tomcat & Cayenne in between my software and the JVM, then I get a tad confused
with what is going on.
What I have been reading today tells me that the "rule of thumb" is to simply
increase memory. However, I have two conflicting thoughts about this:
1. if I do, in fact, have an error in my code then increasing memory
will simply hide the error for a while.
2. if you look at it like an operating system, if you try to run OSX on
a computer with 128MB of ram, then you are insane - and no amount of correct
programming will allow your app to run without running out of memory.
As to your questions: the stack trace was not terribly helpful since it
indicated an out of memory error when a query was launched (on a table that had
all of 7 items in it).
Your idea of trying to set up a similar config on my dev server may be a good
idea. I probably need to take a look at the general health of the memory
management. Of course, I could just be running with way too-little memory.
I wonder what a good base memory setting should be: 64, 128, 512, 1Gig? The
comments on the web seem to indicate all of them.
Thanks
Joe
On Mar 13, 2012, at 3:19 PM, Mike Kienenberger wrote:
> If you have almost no activity, why not set up a duplicate environment
> running the same version of Tomcat and hit your application using
> JMeter or some other testing tool?
>
> Or perhaps you can get sent the application http access.log file and
> duplicate the exact series of requests that generated the problem in
> your dev environment.
>
> That said, Tomcat did often seem to have intrinsic memory issues,
> which is another reason I stopped using a few years back.
>
> Also, you might want to ask what the exact stacktrace is. We've had
> situations where it was a Tomcat permgen memory issue. See this
> article for details -- there are more details in the comments by
> others:
>
> http://www.mkyong.com/tomcat/tomcat-javalangoutofmemoryerror-permgen-space/
>
> Again, a disclaimer as I haven't used Tomcat personally in a while,
> although some of my colleagues continue to do so for development. And
> we don't run app servers using it.
>
>
> On Tue, Mar 13, 2012 at 2:59 PM, Joe Baldwin <[email protected]> wrote:
>> OK, I think that I may have run into this before. The ultimate "solution"
>> was to increase memory - however, I am concerned that may have been a
>> quick-fix and not a long-term fix.
>>
>> The problem is out of memory errors associated with tomcat heap.
>>
>> I have a webapp (powered primarily by cayenne). The database has *very*
>> little in it. I am essentially serving data (via cayenne & tomcat) and
>> images (via tomcat).
>>
>> I have a private tomcat instance running on a webhost in a "shared"
>> environment. What this means is that I *absolutely* cannot attach a
>> profiler.
>>
>> I am being told by the webhost IT people (who are not always accurate in
>> their objectivity) that my app is leaking memory (badly), and that is what
>> caused tomcat to crash.
>>
>> My intuition tells me that with almost no activity on the website (because
>> it is not live yet) and Cayenne memory management that I should be able to
>> manage memory well, but it is not the case.
>>
>> So, if my goal is to determine what the problem is, and if I simply increase
>> heap size, won't I just be masking a potential problem? i.e. if the app
>> runs fine for a while, then mysteriously causes tomcat to run out of heap
>> space, then couldn't there be a memory leak?
>>
>> If there is a memory leak, and I don't see it on my development server, and
>> I *can't* use a profiler on my webhost, then how do I get visibility into
>> the memory usage?
>>
>> Thanks
>> Joe
>>
