[mod-lisp-devel] Error reading from Lisp (?)

[Marc Battyani]

"Edi Weitz" <edi at agharta.de> wrote:
>
> I'm currently having some trouble with a long-running TBNL/mod_lisp
> application on a public website which gets about 500,000 requests per
> month.  It's an application delivered with LispWorks professional
> 4.4.6 and it runs on Linux behind Apache 2.0.54.
>
> >From time to time I see errors in the server log file and sometimes
> (very rarely) users also have reported errors.  It turns out they're
> all of the "error reading from Lisp" kind.  I hacked mod_lisp2.c a bit
> to make this more specific and I now get one of "error reading from
> Lisp (fill status)" or "error reading header name."  This means that
> the error happens either when the reply entity is copied from Lisp to
> the client or when mod_lisp tries to read a header name from Lisp.
>
> I've attached a couple of these error message to the end of this
> email.  What's suspicious for me is that they almost always come in
> chunks - half a dozen of them or more in a couple of seconds, then
> several hours without errors.
>
> I'm calling MARK-AND-SWEEP from time to time but at intervals that
> don't match the time of the error messages.  (My first thought was
> that a full GC blocks LW long enough for mod_lisp to time out but that
> doesn't seem to be the case.)  Other than that I only use locks in
> admin parts of the website which are clearly not used in the middle of
> the night when some of these errors happened.
>
> I'm lost.  Does anyone have an idea where I should look to find the
> cause for these problems?

Have you tried to log the time taken to process the mod_lisp command in Lisp (internally
in the Lisp process) to see if there is a correlation with the Apache errors ?

Marc