Re: Out-of-Memory Handling in Long-Running / Server Applications

You can't really force GC - calling System.gc() is only a request for garbage 
collection. But you can use the MemoryMXBean as described in 
http://www.javaspecialists.eu/archive/Issue092.html to do the memory cleanup 
when you're approaching zero heap rather than when you're actually there.

Burt

On Sunday 13 April 2008 11:41:14 am Randall R Schulz wrote:
> Hi,
>
> My application has highly variable running times and memory demands
> based on the problems submitted to it. Some hard-to-solve (or
> insoluble) problems will run it out of memory.
>
> When memory is exhausted in the inner loop of the program (the only
> place it's going to happen), I catch the OutOfMemoryError, release the
> storage, trigger a GC (forcing it would seem desirable, but I'm not
> sure how to do that) and report the failure back up the call chain.
> The vast majority of the RAM is used in the search tree, which is
> linked only upwardly from the leaves and the leaves are all in a
> priority queue, so relinquishing the priority queue is enough to make
> all the objects in the tree unreferenceable.
>
> This technique sometimes works and sometimes does not. I.e., when it
> doesn't work the program gets another OOM very shortly after or during
> the my OOM handling and dies.
>
> Until recently, this application was mostly run from the command line so
> this behavior was not such a big problem. Now it's being used much more
> in its Web-App form (running in Tomcat 5.5, at the moment), this
> inadequate handling is becoming a problem.
>
>
> What techniques are available for handling OOM errors in situations
> where simply dying on the spot is not an option?
>
>
> Thanks.
>
> Randall Schulz
>
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