best way to design user-defined hook system (handling async errors)

[Lee Aylward]

Hi Marc,

I'm a big fan of AnyEvent, and have built a small web-scraping framework with it (http://noembed.com). Much of the app is defined as separate components that work as plugins; registering URL patterns that they can handle. If a component matches, it is run with a callback to call when complete.

The problem with this design is that there is very little that can be done if a component dies inside of one of it's own asynchronous callbacks (e.g. AE::HTTP, AE::timer). Here is an example of the problem I'm running into:

https://gist.github.com/4645022

I realize this could be somewhat mitigated by passing in a Condvar and requiring the component to catch any errors and then call $cv->croak.

Is there *any* way to handle errors like the one linked above, without requiring the hook to eval everything, and use a Condvar? I'd really like to keep the hook definitions as simple as possible, requiring no knowledge of the internals of the app.

I took a brief look at doing "local $SIG{__DIE__} = sub { $cv->send };" before calling the hook, but it appears that the local die handler is no longer defined when the hook's timer callback is called.

Thanks for any insights!
-- 
Lee Aylward
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