[Lispweb] debugging and serving web pages at the same time in lisp (specifically clisp)

Yin-So Chen yinso.chen at gmail.com
Thu Oct 5 00:41:10 CDT 2006

Hi lisp gurus-

sorry if this (newbie) question has been asked before - I tried to search
for the information on the web but can't (probably because it's hard to tell
what the keyword is).  I am wondering if it is possible to debug and serve
webpage at the same time in lisp (specifically clisp) and verify my

The reason I am wondering is that I've read Paul Graham's note on his
experience in viaweb he was able to diagnose a problem while the customer is
on the phone.  His statement implies that he was running a separate instance
of the website (so not the same one as the customer's looking at), but he
attempt to reproduce the problem and can fix it at the same time (all
appearing without having to shutdown the production image).

You can find the excerpt here:

After playing a bit with araneida's example - it seem that with clisp this
is not possible - because (host-serve-events) blocks repl.  I didn't try
this on SBCL, but assuming it has multi-threads I can see it being a

Another way I can think of is that he built an abstraction layer that allow
him to work from repl to reproduce a problem discovered through a web server
request, so he can work in session to fix the problem, but I can't see how
he can update the running clisp image without having to kill the current web
server session (assuming he has something that works similar to araneida)
and reload code.

Please let me know if I am missing something obvious.  While I don't know if
I agree with the practice of directly changing production code in real-time,
the concept is intriguing, and certainly would be great to know how it's

Oh - I am using clisp now as I am doing work on windows.  I might move to
sbcl on linux but certainly would love to understand how it's done.

Thanks for any comments,
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