RE: Memory Leak Problems in v1.0.1 w/selectPath()

There is a bug open against select path in a multi-threaded env causing
a JavaLangIllegalStateException:
http://issues.apache.org/jira/browse/XMLBEANS-84

This could be related to the memory leak issue that Murali and Venkatesh
have found. Thanx, Jacob for pointing this out to me.

Jamie

-----Original Message-----
From: Jamie Zyskowski 
Sent: Wednesday, January 05, 2005 9:51 AM
To: dev@xxxxxxxxxxxxxxxxxxx
Cc: muvar33@xxxxxxxxx; svejb@xxxxxxxxx
Subject: FW: Memory Leak Problems in v1.0.1 w/selectPath()

Hi dev list,

Murali and Venkatesh (see user list thread below) are working on a
project that uses a compiled schema in a web application. They are
finding memory leaks while calling selectPath() in a custom ThreadPool
(all the threads are pulled out from a custom thread pool). They are
using v1.0.3. The schema is  attached.

The main question they have is:
> What is the right way to use the "selectPath" in
> XmlObjects in a "Thread Pooled" environment (say in
> Tomcat server) so that there won't be any dangling
> references of xmlbeans objects referenced by the
> Thread Locals.

I'm going to try to put a repro together from the info they have
provided, but I am not familiar with the cursor implementation, so I'm
unable to answer their question about changes to the v1 source code to
fix their problem. Can someone take a look and help them out?

Thanx,
Jamie



-----Original Message-----
From: MV [mailto:muvar33@xxxxxxxxx] 
Sent: Tuesday, January 04, 2005 11:21 PM
To: user@xxxxxxxxxxxxxxxxxxx
Subject: Memory Leak Problems

Hi Jamie,
I have another update.

I did couple of changes in the xmlbeans source code
and the problem has gone. Kindly let me know whether
the changes might have any side effects.

- Modified the t1_CachedCursorData from "private" to
"public" in CursorData
- Added a method in the XmlBeans to reset the
"QNameCache".
public static void resetQNameCache ( )
{
    _threadLocalLoaderQNameCache.set(new
QNameCache(32));
}

Then i added the following snippet in my control
servlet, so that i gets executed before processing the
request.

ArrayList arrList = (ArrayList)
CursorData.tl_CachedCursorData.get();
if( arrList != null) arrList.clear();
 XmlBeans.resetQNameCache();

By doing the above changes the threads are pristine
without any threadlocal data due the earlier
"selectpaths" and now those objects are getting
garbage collected properly.

I will be doing some further testing tomorrow morning.

Would this cause any issues ? 

thanks
Murali
--- MV <muvar33@xxxxxxxxx> wrote:

> Hi Jamie,
> Myself and Venkatesh are working on the same
> project.
> We did some further analysis and here is our update.
> 
> We tried to create a test program to load these xmls
> and do some "selectPath" on these XmlObjects. We
> created multiple threads and did quite a number of
> select paths. In all these cases the "Cursor"
> objects
> where perfectly garbage collected. But when we try
> to
> run the same test using a "ThreadPool" (all the
> threads are pulled out from a custom thread pool )
> we
> noticed these "Cursor" objects were not garbage
> collected.
> 
> We profiled them and noticed the following. All the
> org.apache.xmlbeans.impl.store.Cursor instances has
> incoming reference from
> org.apache.xmlbeans.impl.store.Root$ChangeClient.
> There seems to be too many of these
> "Root$ChangeClient" and finally they are referenced
> by
> org.apache.xmlbeans.impl.store.Root which in turn is
> referenced by
> org.apache.xmlbeans.impl.store.CursorData  which is
> stored in the "ThreadLocal". Hence none of them are
> Garbage collected.
> 
> We walked the source code of "Cursor" and noticed
> that
> every time we do a 'selectPath' it is trying to
> register itself to the "Root" thru the
> "Root$ChangeClient". We removed this dependency and
> tested it . Now the "Cursors" are garbage collected,
> but still we see
> org.apache.xmlbeans.impl.store.Splay$Begin and other
> classes.
> 
> Not sure whether we are hitting in right direction. 
> 
> What is the right way to use the "selectPath" in
> XmlObjects in a "Thread Pooled" environment ( say in
> Tomcat server) so that there won't be any dangling
> references of xmlbeans objects referenced by the
> Thread Locals. 
> 
> Any pointers would be very much appreciated.
> 
> thanks
> MV
> 
> 
> 
> Date: Tue, 4 Jan 2005 10:44:57 -0800 (PST)
> From: Java SV <svejb@xxxxxxxxx>
> Subject: Memory Leak Problems
> Content-Type: multipart/mixed;
> boundary="0-2099955324-1104864297=:69138"
> 
> 
> Hi Jamie,
> 
> Thanks again for your quick response. Please find
> the
> schema attached.
> 
> Thanks,
> Venkatesh
> 
> --- Jamie Zyskowski <jzyskows@xxxxxxx> wrote:
> 
> > Hi Venkat,
> > 
> > Could you provide the schema you compiled to get
> > these xmlbean classes?
> > With it, I can try to create a repro scenario.
> > 
> > Thanx,
> > Jamie
> > 
> > -----Original Message-----
> > From: Java SV [mailto:svejb@xxxxxxxxx] 
> > Sent: Monday, January 03, 2005 5:54 PM
> > To: user@xxxxxxxxxxxxxxxxxxx
> > Cc: Jamie Zyskowski; svejb@xxxxxxxxx
> > Subject: RE: Memory Leak Problems
> > 
> > Hi Jamie,
> > 
> > Thanks for your response. 
> > 
> > We use XMLBeans as a Java Data Binding tool to
> > essentially load the XML documents and get the
> > objectified representation of XML.
> > 
> > Environment: Tomcat 5.0.16, Solaris as well as
> > Windows
> > 2000
> > 
> > Sample Code:
> > 
> >     URL urlHits = new URL(hitsURL); // Get the XML
> > Stream
> >     InputStream inputStream =
> > urlHits.openConnection().getInputStream();
> > 
> >     HITSDocument hitsDocument =
> > HITSDocument.Factory.parse(inputStream);
> > 
> >     HITSDocument.HITS body =
> hitsDocument.getHITS();
> >     HITSDocument.HITS.MSGHEAD msgHead =
> > body.getMSGHEAD();
> > 
> >     HITSConnection hitsConnection = null;
> >     if (msgHead == null) { // Connection Creation
> is
> > Success
> >        hitsConnection = new HITSConnection();
> >        XmlObject[] xmlObjects =
> > body.getGENHEAD().selectPath("CONNID");
> >       
> >
>
hitsConnection.setConnectionID(((XmlObjectBase)xmlObjects[0]).getStringV
> > alue());
> >     } else {
> >        String errorCode =
> > translateHitsErrorCode(msgHead.getMSGCODE(),
> > HITSErrorCodes.CONNECTION_NOT_AVAILABLE);
> >        throw new HITSRuntimeException(errorCode);
> >     }
> > 
> > We basically peek into the result XML and look for
> > certain elements of interest. Never get explicit
> > cuursors but only execute a bunch of selectPath()
> > methods.
> > 
> > We finally call xmlObject.newDomNode() to send the
> > result Node to the XSLT Transformer.
> > 
> > Again, your help is greatly appreciated.
> > 
> > Thanks,
> > Venkat
> 
> 
>               
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