RE: Barracuda: Re:Barracuda Memory troubles

Hi Steve!

> This may seem like a stupid question but...

Nah...no such think as a stupid question, except maybe for the one that
doesn't get asked ;-)

> I think I'm missing something quite basic about how Barracuda is
> supposed to
> work.  What state should be saved in the session:
>  1) The models (almost certainly)
>  2) The BComponent tree (seems of little value without #3)
>  3) The rendered DOM tree.

Well, first of all, I want to say that in practice here at ATMReports we
don't keep any of these beyond a single req-resp lifecycle. If we did want
to cache something, we would not cache the model but rather the data that
backs the model, and then just create a new model (using that same data as
input) for every request.

> If the BComponent's are not being kept past the request / response cycle
> why would they care about changes to the model? That is if you create a
> new BComponent to construct a page it starts out invalid so you should
> never see the valid state in a BComponent?

If you are not caching components, then I think you are correct - the
hierarchy is always invalidated, so it doesn't really matter. The component
model does, however, allow for caching of components (as per the BConfig
example) - I don't really recommend doing it this way, but it is doable, and
that's why the model notification is in there.

That help?

Christian

----------------------------------------------
Christian Cryder [[email protected]]
Internet Architect, ATMReports.com
Barracuda - http://barracuda.enhydra.org
----------------------------------------------
"Coffee? I could quit anytime, just not today"


> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of Mayhew, Steve
> Sent: Monday, December 09, 2002 12:17 PM
> To: '[email protected]'
> Subject: RE: Barracuda: Re:Barracuda Memory troubles
>
>
>
> This may seem like a stupid question but... If the BComponent's are not
> being kept past the request / response cycle why would they care about
> changes to the model?   That is if you create a new BComponent to
> construct
> a page it starts out invalid so you should never see the valid state in a
> BComponent?
>
> I think I'm missing something quite basic about how Barracuda is
> supposed to
> work.  What state should be saved in the session:
>  1) The models (almost certainly)
>  2) The BComponent tree (seems of little value without #3)
>  3) The rendered DOM tree.
>
> Unless we are to surgically update the DOM on the browser it seems a
> rendered DOM tree is either entirely valid or entirely invalid...
>  The only
> choice is to return a complete HTML page to the client or status 304 (if
> client does a conditional GET)
>
> Given this why have the BComponents listen to models at all?
>
> One approach might be to make the model's reference to listeners a
> WeakReference, that way once the BComponent that references them is no
> longer strongly referenced then it will be GC'd and the WeakReference will
> be null'd.  Model can simply ingore (or better remove from the list) any
> weakly reachable (get() returns null) BComponent objects.
>
> Just my random thoughts.
>
>
> > -----Original Message-----
> > From: Vas Skrypnyk [mailto:[email protected]]
> > Sent: Sunday, December 08, 2002 11:44 PM
> > To: [email protected]
> > Subject: RE: Barracuda: Re:Barracuda Memory troubles
> >
> >
> > Hi Christian,
> >
> > >Hi Bill,
> > >
> > >So it sounds like you release your handle to the BTemplate,
> > but the Model
> > >still has a reference to it, which in turn would keep the
> > BTemplate (and any
> > >components it contains) from being
> > >gc'd, since your model still has
> > >references to them. Is that correct?
> >
> > That's correct.
> >
> > >It almost sounds like when a component calls the
> > destroyCycle() method, it
> > >needs a mechanism to disconnect any models which might
> > >be listening to that
> > >component. Thoughts?
> >
> > That sounds right. If destroyCycle() is called as the
> > finalization code on the BTemplate object then, since it has
> > references to all its models it should be able to disconnect
> > itself. It will still be possible to hook in the same model
> > to the same BTemplate and get the listener connection
> > replicated, but, I suppose, the programmers should take some
> > responsibility for their code :))
> >
> > Cheers,
> > --Bill.
> >
> > >Christian
> > >----------------------------------------------
> > >Christian Cryder [[email protected]]
> > >Internet Architect, ATMReports.com
> > >Barracuda - http:
> > >//barracuda.enhydra.org
> > >----------------------------------------------
> > >"Coffee? I could quit anytime, just not today"
> > >
> > >
> > >> -----Original Message-----
> > >> From: [email protected] [mailto:barracuda-
> > >[email protected]]On
> > >> Behalf Of V B Skrypnyk
> > >> Sent: Saturday, December 07, 2002 10:17 PM
> > >> To: [email protected]
> > >> Subject: Barracuda: Re:Barracuda Memory troubles
> > >>
> > >>
> > >> Christian,
> > >>
> > >>
> > >I have found where the memory leak was happening in my code. It
> > >> is caused by the following scenario:
> > >>
> > >> 1. Create a BTemplate that will last for one servlet lifecycle
> > >> (MainScreen).
> > >> 2. Create
> > >a Model that represents some persistent data and store
> > >> it in the session (Tabs)
> > >> 3. Have different portions of your application access
> > >> session-saved Model and set up their data in it. (Tabs)
> > >
> > >> 4. On every MainScreen instantiation add the model, so that the
> > >> respective portion of the template is rendered, i.e. Tabs.
> > >>
> > >> What happens now is that on every addModel() call a new listener
> > >
> > >> is added to the model and the list keeps growing until the model
> > >> drags around megabytes of listeners, as happened in my case.
> > >>
> > >> Now, maybe instead of appending the listeners in the List it is
> > >
> > >> worthwhile checking if this listener has already been added, or
> > >> maybe I am misusing the Barracuda framework.
> > >>
> > >> Please let me know what you think.
> > >>
> > >> Cheers,
> > >> --Bill.
> > >> _______________________________________________
> > >
> > >> Barracuda mailing list
> > >> [email protected]
> > >> http://www.enhydra.org/mailman/listinfo.cgi/barracuda
> > >> FAQ - http://www.jguru.com/faq/Barracuda
> > >
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