Question on component caching / reuse

[Franck Routier]

[re-sent - didn't make it to the list ?]

Hi all,

I have a question regarding components reuse or caching. After looking
at the code, I have the feeling that at the end of the rendering phase,
destroyCycle() is called on every component. This will null references
to children, views, ... So it seems to me that it would be difficult to
cache / reuse components (in a servlet session, for example for a part
of the UI like a toolbar).

So here is my question :

- does anyone cache components in his/her app (ie reuse the same
instance of a component on several request/response cycles) ?

- does anyone remember if this is supposed to be possible or not ? On
that matter, I have found a tread on the subject here :
http://osdir.com/ml/java.enhydra.barracuda.general/2002-11/msg00084.html
(but well, it was in 2002...)

- is this desirable ? If not why ?

- should the destroyCycle() be more more conservative, ie destroy only
references to stepChildren (not regular children) or tempViews (not
regular views) ? destroyCycle() is here to prevent memory leaks, so I
would rather be conservative with it, but maybe it could be enhanced to
promote components reuse...

Any thought on this ?

Franck






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[Denny Chambers]

Component caching doesn't sound bad, as long as it can be turned off. In
fact since it wasn't on before, it should be off by default. I can see
where this could be very useful. Our applications current way of
rendering pages includes what we call our MasterTemplate. This template
sets up the overall look of our page. i.e. it create context sensitive
menus, titles, icons, style sheets, etc.... Then we have individual
pages with supplies the content. I can see where caching this master
template would be advantageous, as long as we could render it with a new
model on each request. For my particular use of Barracuda, we are
somewhat limited on memory usage, doing a lot of in-memory caching would
not be too good for me.

Denny

Franck Routier wrote:

> [re-sent - didn't make it to the list ?]
>
> Hi all,
>
> I have a question regarding components reuse or caching. After looking
> at the code, I have the feeling that at the end of the rendering phase,
> destroyCycle() is called on every component. This will null references
> to children, views, ... So it seems to me that it would be difficult to
> cache / reuse components (in a servlet session, for example for a part
> of the UI like a toolbar).
>
> So here is my question :
>
> - does anyone cache components in his/her app (ie reuse the same
> instance of a component on several request/response cycles) ?
>
> - does anyone remember if this is supposed to be possible or not ? On
> that matter, I have found a tread on the subject here :
> http://osdir.com/ml/java.enhydra.barracuda.general/2002-11/msg00084.html
> (but well, it was in 2002...)
>
> - is this desirable ? If not why ?
>
> - should the destroyCycle() be more more conservative, ie destroy only
> references to stepChildren (not regular children) or tempViews (not
> regular views) ? destroyCycle() is here to prevent memory leaks, so I
> would rather be conservative with it, but maybe it could be enhanced to
> promote components reuse...
>
> Any thought on this ?
>
> Franck
>
>
>
>  
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[Franck Routier]

Hi Denny,

you get the point of what I am meaning : not really caching components
in the sense that Barracuda would do that beyond the scene without the
developper taking care of it, but rather giving the developper the
opportunity to reuse an instance of a component during several req/resp
cycles (of course with updated models backing them if needed).

Right now this is simply impossible and leads to NPE in several places
in Barracuda.

I have tried to modify destroyCycle() on my local copy of Barracuda by :
- not setting children to null but rather call removeAllStepChildren()
- not setting view to null but rather call removeAllViews()
- not setting parent to null but rather let removeChildren() do that on
removed children...

I don't know what to do with statemap and with models for components
backed by models...

So far this enables me to reuse components, but the whole point is to
avoid reopening memory leaks in Barracuda...

What I have in mind is that only the developpers should use addChild().
Then he/she would be responsible for removing them when necessary (maybe
Barracuda should provide a deepDestoyCycle method or something).
The framework would only use addStepChild() and stepChildren would be
removed after each rendering.

I will makes tests and try this... but any comment is welcome, as I am
not too sure I not opening Pandora's box :)

Franck



Le samedi 26 mai 2007 à 09:03 -0500, Denny Chambers a écrit :

> Component caching doesn't sound bad, as long as it can be turned off. In
> fact since it wasn't on before, it should be off by default. I can see
> where this could be very useful. Our applications current way of
> rendering pages includes what we call our MasterTemplate. This template
> sets up the overall look of our page. i.e. it create context sensitive
> menus, titles, icons, style sheets, etc.... Then we have individual
> pages with supplies the content. I can see where caching this master
> template would be advantageous, as long as we could render it with a new
> model on each request. For my particular use of Barracuda, we are
> somewhat limited on memory usage, doing a lot of in-memory caching would
> not be too good for me.
>
> Denny
>
> Franck Routier wrote:
> > [re-sent - didn't make it to the list ?]
> >
> > Hi all,
> >
> > I have a question regarding components reuse or caching. After looking
> > at the code, I have the feeling that at the end of the rendering phase,
> > destroyCycle() is called on every component. This will null references
> > to children, views, ... So it seems to me that it would be difficult to
> > cache / reuse components (in a servlet session, for example for a part
> > of the UI like a toolbar).
> >
> > So here is my question :
> >
> > - does anyone cache components in his/her app (ie reuse the same
> > instance of a component on several request/response cycles) ?
> >
> > - does anyone remember if this is supposed to be possible or not ? On
> > that matter, I have found a tread on the subject here :
> > http://osdir.com/ml/java.enhydra.barracuda.general/2002-11/msg00084.html
> > (but well, it was in 2002...)
> >
> > - is this desirable ? If not why ?
> >
> > - should the destroyCycle() be more more conservative, ie destroy only
> > references to stepChildren (not regular children) or tempViews (not
> > regular views) ? destroyCycle() is here to prevent memory leaks, so I
> > would rather be conservative with it, but maybe it could be enhanced to
> > promote components reuse...
> >
> > Any thought on this ?
> >
> > Franck
> >
> >
> >
> >  
> > ------------------------------------------------------------------------
> >
> >
> > --
> > Barracuda mailing list
> > Barracuda@...
> > http://www.objectweb.org/wws/lists/projects/barracuda
> >  
>
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