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From Marcus Crafter <craft...@fztig938.bank.dresdner.net>
Subject Re: AW: [C2] sitemap creation threading issue ?
Date Mon, 20 Aug 2001 15:05:43 GMT
Hi Carsten,

	Thanks for your help mate. I'll check out the changes you made. :-)

	Cheers,

	Marcus

On Mon, 20 Aug 2001, Carsten Ziegeler wrote:

> I just updated the logic a little bit, the threads are now
> only blocked (synchronized) when no sitemap is available.
> 
> This new code is a little bit confusion but it should work.
> 
> Carsten
> 
> > -----Urspr√ľngliche Nachricht-----
> > Von: Morrison, John [mailto:John.Morrison@uk.experian.com]
> > Gesendet: Montag, 20. August 2001 14:05
> > An: 'cocoon-dev@xml.apache.org'
> > Betreff: RE: [C2] sitemap creation threading issue ?
> >
> >
> > Yeah, and only on the huge box :(
> >
> > I've a tiddly little development server which is smaller than my
> > dev box but
> > is under my control and a whacking huge 'stage' set of machines.  I'm
> > getting better performance from my dev boxes than a
> > multi-processor which a
> > gig or so of memory!
> >
> > > -----Original Message-----
> > > From: Carsten Ziegeler [mailto:cziegeler@sundn.de]
> > > Sent: Monday, 20 August 2001 1:03 pm
> > > To: cocoon-dev@xml.apache.org
> > > Subject: AW: [C2] sitemap creation threading issue ?
> > >
> > >
> > > Hi John,
> > >
> > > do you mean 5 seconds or 5 milliseconds?
> > > I fear you mean seconds, right?
> > >
> > > Carsten
> > >
> > >
> > >
> > > > -----Urspr√ľngliche Nachricht-----
> > > > Von: Morrison, John [mailto:John.Morrison@uk.experian.com]
> > > > Gesendet: Montag, 20. August 2001 13:47
> > > > An: 'cocoon-dev@xml.apache.org'
> > > > Betreff: RE: [C2] sitemap creation threading issue ?
> > > >
> > > >
> > > > Hi all, esp Marcus,
> > > >
> > > > I too have been running Load tests, I also noticed that
> > > 'something' was
> > > > happening regularly to slow the response.  I hadn't gotten round
> > > > to checking
> > > > the code though (the testing machines are isolated - 0 access
> > > > from/to my dev
> > > > station).
> > > >
> > > > I saw your patch and rejoiced ;) but it's taken the
> > > response of some of my
> > > > pages from a couple of hundred milliseconds to over 5!  I've not
> > > > yet looked
> > > > at _what_ your patch did, but have you seen a similar
> > > increase in time?
> > > >
> > > > J.
> > > >
> > > > > -----Original Message-----
> > > > > From: Carsten Ziegeler [mailto:cziegeler@sundn.de]
> > > > > Sent: Monday, 20 August 2001 7:57 am
> > > > > To: cocoon-dev@xml.apache.org
> > > > > Subject: AW: [C2] sitemap creation threading issue ?
> > > > >
> > > > >
> > > > > Hi Marcus,
> > > > >
> > > > > thanks for your patch. I applied it, please cross check :-)
> > > > >
> > > > > Carsten
> > > > >
> > > > > > -----Ursprungliche Nachricht-----
> > > > > > Von: Marcus Crafter [mailto:crafterm@fztig938.bank.dresdner.net]
> > > > > > Gesendet: Samstag, 18. August 2001 22:41
> > > > > > An: Cocoon Developers Mailing List
> > > > > > Betreff: [C2] sitemap creation threading issue ?
> > > > > >
> > > > > >
> > > > > > Hi *,
> > > > > >
> > > > > > 	Hope all is well.
> > > > > >
> > > > > > 	Michael and I have spent the day testing our C2
> > > application with
> > > > > > 	LoadRunner and have potentially uncovered a threading
> > > > > problem during
> > > > > > 	sitemap creation.
> > > > > >
> > > > > > 	We're not experts with the code but from our
> > > understanding the
> > > > > > 	following is happening, please let us know if we are
> > > > > right/wrong:
> > > > > >
> > > > > > 	There seems to be a problem with the getHandler()
> > > > > method, located in
> > > > > > 	the sitemap Manager class (line 154).
> > > getHandler() attempts
> > > > > > to access a
> > > > > > 	sitemap handler object for each request for
> > > processing. If
> > > > > > the handler
> > > > > > 	object is not available it creates one, causing the
> > > > > sitemap to be
> > > > > > 	generated.
> > > > > >
> > > > > > 	We've noticed under load, that many handler objects are
> > > > > created for
> > > > > > 	the same sitemap. This is because getHandler() does not
> > > > > protect the
> > > > > > 	following lines:
> > > > > >
> > > > > > 		Handler sitemapHandler =
> > > (Handler)sitemaps.get(source);
> > > > > >
> > > > > > 	and
> > > > > >
> > > > > > 		sitemaps.put(source, sitemapHandler);
> > > > > >
> > > > > > 	as a critical area.
> > > > > >
> > > > > > 	If multiple concurrent threads pass through
> > > > > getHandler() which are
> > > > > > 	requests for resources from the same sitemap,
> > > the first line
> > > > > > 	above will return null multiple times causing the same
> > > > > sitemap to be
> > > > > > 	compiled several times, each by individual
> > > Handler objects.
> > > > > >
> > > > > > 	This happens because sitemaps.put() executes after each
> > > > > > sitemap handler
> > > > > > 	object is created (which can take time for
> > > large sitemaps),
> > > > > > and cannot
> > > > > > 	prevent other incoming threads from waiting until it
> > > > > adds the newly
> > > > > > 	created handler object into the 'sitemaps' hashmap.
> > > > > >
> > > > > > 	When we synchronized the getHandler method to
> > > protect the
> > > > > > 	getting/setting of the sitemaps hashmap, we saw
> > > that the sitemap
> > > > > > 	handler object was created only once, and that
> > > the application
> > > > > > 	performed much better under load. Previously the same
> > > > > > sitemap handler
> > > > > > 	object was created as many times as we had
> > > simultaneous threads
> > > > > > 	make requests.
> > > > > >
> > > > > > 	Attached is a diff of the change we made. There might
> > > > > be a better
> > > > > > 	solution as the Handler class seems to be built to
> > > > > handle this, it's
> > > > > > 	just that the allocation of a new Handler objects per
> > > > > > sitemap, defeats
> > > > > > 	it's internal multi-thread logic.
> > > > > >
> > > > > > 	Any comments/thoughts/suggestions ?
> > > > > >
> > > > > > 	Cheers,
> > > > > >
> > > > > > 	Marcus
> > > > > >
> > > > > > --
> > > > > >         .....
> > > > > >      ,,$$$$$$$$$,      Marcus Crafter
> > > > > >     ;$'      '$$$$:    Computer Systems Engineer
> > > > > >     $:         $$$$:   Open Software Associates GmbH
> > > > > >      $       o_)$$$:   82-84 Mainzer Landstrasse
> > > > > >      ;$,    _/\ &&:'   60327 Frankfurt Germany
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69 9757 200
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-- 
        .....
     ,,$$$$$$$$$,      Marcus Crafter
    ;$'      '$$$$:    Computer Systems Engineer
    $:         $$$$:   Open Software Associates GmbH
     $       o_)$$$:   82-84 Mainzer Landstrasse
     ;$,    _/\ &&:'   60327 Frankfurt Germany
       '     /( &&&
           \_&&&&'     Email : Marcus.Crafter@osa.de
          &&&&.        Business Hours : +49 69 9757 200
    &&&&&&&:


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