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From "Carsten Ziegeler" <cziege...@sundn.de>
Subject AW: [C2] sitemap creation threading issue ?
Date Mon, 20 Aug 2001 12:03:12 GMT
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
> > >        '     /( &&&
> > >            \_&&&&'     Email : Marcus.Crafter@osa.de
> > >           &&&&.        Business Hours : +49 69 9757 200
> > >     &&&&&&&:
> > >
> >
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