RE: Memory Leak issue -- FOP

[Dominik Stadler]

Hi, 

Craig is right, it's it's not a "memory leak", but rather memory kept active 
too long, i.e. after processing is done. I saw the same thing when I integrated 
FOP into an application over here.

It is basically caused by the SAX implementation that you use as it caches the 
SAX-Handler, where the FOP-SAX-Handler keeps references to a lot of internal 
stuff. In my case it did this in a ThreadLocal, so with different threads using 
FOP I ended up having this memory kept in every thread, which accumulated to 
quite an amount of memory depending on the usage pattern.

I tried various different ways to solve this, when using SAX/XML provided as 
part of Sun JDK 1.6 the following was removing this memory bloat:

                Result result = new SAXResult(fop.getDefaultHandler());
                SAXSource source = new SAXSource(inputSource);
                // set our own XMLReader to prevent Sun XML from caching stuff 
in ThreadLocals which keeps FOP in memory
                // we want to free up any FOP resources when not reporting and 
for this ThreadLocals is very bad, especially
                // as we are called in different threads via REST and 
Scheduling thread pools!
                source.setXMLReader(XMLReaderFactory.createXMLReader());

                transformer.transform(source, result);

                if (logger.isLoggable(Level.FINE) && fop.getResults() != null) {
                        logger.info("Processing resulted in " + 
fop.getResults().getPageCount() + " pages."); //$NON-NLS-1$ //$NON-NLS-2$
                }
        }

Maybe a similar thing solves this for you as well.

Dominik.


-----Original Message-----
From: Craig Ringer [mailto:cr...@postnewspapers.com.au] 
Sent: Donnerstag, 26. August 2010 02:35
To: fop-users@xmlgraphics.apache.org
Cc: Hamed Mohammed
Subject: Re: Memory Leak issue -- FOP

On 26/08/2010 3:39 AM, Hamed Mohammed wrote:
> Hello Users:
> Any idea on how to solve the FOP memory leak issue. Below snap shots are
> taken from Eclipse Memory Analyzer of a IBM portable heap dump.

What makes you think that's a memory leak?

It's a large amount of memory consumption, sure. But is there any 
evidence it's growing over time? Or growing whenever a new document is 
processed, without shinking again when the document is finished?

How do you know it's not your own code keeping references to the fop 
instances around? Can you produce a small, self-contained program that 
demonstrates the leak?

If your real question is "why is FOP using so much memory" ... well, to 
answer that it'd be necessary to know more about your XSL-FO input and 
the associated resources like graphics.

-- 
Craig Ringer

Tech-related writing at http://soapyfrogs.blogspot.com/

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