[hunchentoot-devel] New releases of Hunchentoot, Drakma, and Chunga

[Andreas Fuchs]

On Fri, Feb 20, 2009 at 12:34, Jochen Schmidt <jsc at crispylogics.com> wrote:
>> *BREAK-ON-SIGNALS* is better than what Hunchentoot previously had -
>> You're sent to a the debugger, making actual analysis possible, and
>> the technique works everywhere, not just in Hunchentoot.
>
> Thats actually not a feature. With *catch-errors-p* you ended up
> within an debugger too and it was actually a good thing that it was
> restricted to hunchentoot. *break-on-signals* is definitely the wrong
> tool to do that! Following the dev-tree for some time now I have just
> setup my own error handling using handler-bind in a custom dispatcher
> - similar to what Edi outlined in his answer. It should at least be
> documented how to properly install such a hunchentoot specific error-
> handler, because it might not be obvious to everyone. The new
> hunchentoot is meant to be more customizable - it actually is, because
> of fantastic the merits of CL like handler-bind - It would have been
> nicer (from a library designer perspective) to have this integrated
> within the protocols though.

So, I just spent a few hours (successfully) hemming and haw-ing about
how to put these suggestions into real code, and this is what I came
up with:

;;; An acceptor that invokes the debugger on errors:
(defclass debuggable-acceptor (hunchentoot:acceptor)
     ())

(defmethod process-connection ((*acceptor* debuggable-acceptor) (socket t))
  (declare (ignore socket))
  (handler-bind ((error #'invoke-debugger))
    (call-next-method)))

(defmethod acceptor-request-dispatcher ((*acceptor* debuggable-acceptor))
  (let ((dispatcher (call-next-method)))
    (lambda (request)
      (handler-bind ((error #'invoke-debugger))
        (funcall dispatcher request)))))

In my development system, I then do (make-instance
'debuggable-acceptor :port 4242) instead of 'hunchentoot:acceptor, and
error conditions pop up a swank debugger again.

Hope this is useful for everyone else,
-- 
Andreas Fuchs, (http://|im:asf@|mailto:asf@)boinkor.net, antifuchs