> From: Pier Fumagalli [mailto:[EMAIL PROTECTED]
>
> Why? If a request fails because I reloaded the XSLT Transformer block,
> well, I'm ready to loose that request... Cocoon is a servlet, at the
> end of the day, and I'd rather loose XSLT translation for 1/2
> a second while I reload the XALAN block, than wait 10 minutes while I
> reload the JVM, as I can't reload XSLT because every single Pipeline
in
> my sitemap is locking on it, and (of course) I will never ever be able
to
> reload it until the traffic on my website goes down to ZERO...
In all read/write lock implementations I've ever seen, having a pending
writer means that readers queue up. That is, you'll have to wait
until all *currently executing pipelines* have finished. Then you'll
get your write lock and can swap the block. All pipelines that
tried to lock the component after your request to acquire a write
lock will have queued up, and will start executing as soon as you
release your write lock.
But the point here wasn't really to argue specific cases, was it?
> Dude, don't get upset, I'm not thinking about the holy grail here, I
> _DO_NOT_WANT_ to write another Avalon, I want Cocoon to have a
> container tailored EXACTLY for its own requirements, being a servlet
> and all...
>
> Let's not forget that we work on HTTP connections, and that at any
> given point in time, those can be disconnected, time out, or your
> network admin can unplug the cable...
>
> What's the difference between that, and loosing the connection for a
> second with a component? Thing, that (by the way) will _NEVER_ happen
> automagically, but only when the administrator decides that it's time
> to reload a block instance?
Because I think that you are trading a little complexity in the
container for a lot of complexity in the blocks.
Then again, that's *my* VHO.
Basically the question is this:
Is the code expected to handle a swap of a block gracefully?
If a block swap really is like unplugging a network cable, or toasting
the switch/router, then code should just re-throw the exception and
exit abruptly. However, if the code is somehow expected to recover, then
I think that there should be some mechanism whereby the swapping is
made invisibly to the code (i.e. when the block isn't used). Otherwise
the amount of error-handling code will become impractical.
/LS
