Graham,
Thank you very much for your quick response and help... very much
appreciated.. see below for my replies..
>
> > I think I read pretty much whatever there is to read about these
> > errors in this group but still cannot understand what is causing this
> > problem in my case..
>
> > Every once in a while (very very rarely, compared to the amount of
> > traffic being served) I get the following error:
>
> Your selection of error log messages is confusing.
I tried to select the lines that show the specific errors that I am
getting from mod_wsgi daemon so that it is not confusing.. I guess I
was wrong :)
>
> > [Wed Jan 06 22:38:31 2010] [warn] (14)Bad address: mod_wsgi
> > (pid=18735): Unable to stat target WSGI script '(null)'.
> > [Wed Jan 06 22:38:31 2010] [alert] (14)Bad address: mod_wsgi
> > (pid=18735): Request origin could not be validated.
>
> Both the above error messages are generated within mod_wsgi daemon
> mode process.
>
> The first error message, because it says '(null)' indicates that
> SCRIPT_FILENAME was missing in data passed to mod_wsgi daemon process
> however I don't understand how that could occur at this point.
>
> The second error message indicates that some mod_wsgi validation to
> protect against malicious attempts to execute arbitrary script as user
> that mod_wsgi daemon process runs has failed. This can be a side
> effect of corruption indicated from message above, or technically
> could indicate an attempt by external code to connect to mod_wsgi
> listener sockets directly and try and fake up requests for execution.
>
> > [Wed Jan 06 22:38:31 2010] [error] [client 3.181.52.54] Premature end
> > of script headers: <script_name>.wsgi
>
> This though now is a likely indicator that mod_wsgi daemon process crashed.
>
> > [Wed Jan 06 22:38:32 2010] [notice] child pid 2710 exit signal
> > Segmentation fault (11)
>
> Problem now is that the pid of the process that crashed doesn't match
> that in which original error messages occurred, thus why it is a bit
> confusing.
Yes, I see it every time the error occurs.. the pids are always
different..
>
> > I have siteminder agent running as well and I notice that bunch of seg
> > fault errors associated to that follows along with malloc errors...
>
> > Here's my configuration:
>
> > Apache/2.0.59 (Unix) mod_jk/1.2.18 mod_wsgi/2.6 Python/2.5.4
> > configured
>
> > WSGIApplicationGroup %{GLOBAL}
> > WSGIDaemonProcess wsgi processes=1 threads=1 display-name=%{GROUP}
>
> You don't need 'processes=1' as will default to single process and
> using 'processes=1' instead of allow it to default has subtle side
> affect of setting 'wsgi.multiprocess' to True. You should only use
> 'processes=1' if load balancing across many Apache instances where
> each has only single process in daemon process group for that
> application.
I have 4 apaches running on the box with the same wsgi configuration..
the box has 4 cores hence 4 apaches.. I have only 3 simple wsgi
scripts running.. one of them is used for testing, another one is
actively used in production and the third one is only hit by a back
end script to refresh data in a singleton object, which is used by
others for only read.. so I guess it is ok to keep processes=1?
>
> > WSGIProcessGroup wsgi
>
> > Any help and insight would be much appreciated..
>
> I can only suggest trying mod_wsgi 3.1.
Just did.. monitoring to see if I get any errors..
>
> Other than that don't really have an answer. It looks like memory
> corruption but whether the source is mod_wsgi, another Apache module
> or a Python C extension module, don't know.
>
> What third party Python modules do you use which may have a C
> extension module component?
>
> Anyway, will have a think about it some more and see if can come up
> with any suggestions of things to look for or try. A snippet of log
> file covering a longer amount of time may be a good point.
>
> Graham
Another question I had was whether slow network connections might
cause this issue.. what are your thoughts on that?
-Cem
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