[hunchentoot-devel] Backtrace display

[Daniel White]

On Thu, 3 Sep 2009 13:44:46 +1000
Daniel White <daniel at whitehouse.id.au> wrote:

> On Wed, 2 Sep 2009 21:54:14 -0400
> Jonathon McKitrick <jmckitrick at gmail.com> wrote:
> 
> > Thanks, I'll check these out.  It looks pretty weblocks-specific, but
> > I assume it can be adapted to hunchentoot easily enough?  I'll just
> > look for a similar method  to wrap with the AROUND method.
> > 
> > On Tue, Sep 1, 2009 at 2:50 PM, Leslie P. Polzer<sky at viridian-project.de> wrote:
> > >
> > > Jonathon McKitrick wrote:
> > >> I recall some time ago, the break and backtrace capability of
> > >> Hunchentoot was removed, perhaps to make it less platform dependent.
> > >> But I still find myself often trying to find the origin of cryptic
> > >> error messages, and adding FORMAT and BREAK statements to narrow down
> > >> the problem area.  What is a good way to drop in support for, say,
> > >> SBCL, so that an error will break into the debugger with a backtrace,
> > >> or even dump the backtrace to the log file?
> > >
> > > See http://bitbucket.org/S11001001/weblocks-dev/src/tip/src/error-handler.lisp
> > > and http://bitbucket.org/S11001001/weblocks-dev/src/tip/src/request-handler.lisp#cl-61
> > >
> > >  Leslie
> 
> For debugging purposes, I've been using the following for a while.  It
> only extends Andreas' suggestion slightly by handling the IO-TIMEOUT
> condition I was experiencing in SBCL.
> 
> ;;; Acceptor that provides debugging from the REPL
> ;;; Based on an email by Andreas Fruchs:
> ;;; http://common-lisp.net/pipermail/tbnl-devel/2009-April/004688.html
> (defclass debuggable-acceptor (acceptor)
>      ()
>   (:documentation "An acceptor that handles errors by invoking the
>   debugger."))
> 
> (defmethod process-connection ((*acceptor* debuggable-acceptor) (socket t))
>   (declare (ignore socket))
>   ;; Invoke the debugger on any errors except for SB-SYS:IO-TIMEOUT.
>   ;; HTTP browsers usually leave the connection open for futher requests,
>   ;; and Hunchentoot respects this but sets a timeout so that old connections
>   ;; are cleaned up.
>   (let ((*debugging-p* t))
>     (handler-case (call-next-method)
>       #+sbcl (sb-sys:io-timeout (condition) (values nil condition))
>       (error (condition) (invoke-debugger condition)))))
> 
> (defmethod acceptor-request-dispatcher ((*acceptor* debuggable-acceptor))
>   (let ((dispatcher (call-next-method)))
>     (lambda (request)
>       (handler-bind ((error #'invoke-debugger))
>         (funcall dispatcher request)))))
> 

I also have a special variable *DEBUGGING-P* defined for some other
special cases I needed, so that can be safely discarded if not needed.

-- 
Daniel White