Why does Django/mod_wsgi crash on certain URL lengths?

Question

I've got a weird problem here: I'm getting a 500 error code from Apache serving a Django 1.1 application when the length of the path part of the URL given to Apache is in [23..26,30..33]. For example, http://server/012345678901234567890123 results in a 500 error while http://server/012345678901234567 does not.

Each 500 error also results in a "Request origin could not be validated." error message from mod_wsgi in the logs. The error doesn't occur on Apache-only URLs, like images, it only happens with Django.

Any idea why this could be happening?

Answer 1

Is it possible that this is an error somewhere in your app's code?

Change your apache settings for the site so that WSGI creates its own error log

LogLevel info
ErrorLog /tmp/error_log

Then run

tail -f /tmp/error_log

And try loading in one of your long URLs. Hopefully the error message will come up in the log file. At the very least, it should pinpoint what the real error is.

Answer 2

Take this to the proper mod_wsgi list on Google Groups and detail what versions of Apache, Python and mod_wsgi you are using. Also indicate which Apache MPM you are using and any other non standard Apache modules you are using. Might be an idea to state whether using 32 bit or 64 bit applications as well.

This error is specific to daemon mode and occurs before it even gets to your WSGI application. Frankly the error should never happen unless there is a measure of memory corruption occurring or some very subtle one off error which for some reason has never occurred with the huge number of existing users.

There has been one other person report this recently. You though seem to have been able to tie it to a specific URL length, which hasn't been suggested before and is a clue at least.

Do note, about to go on holidays. You have less that 8 hours for me to have another serious look at it and after that going to be really hard until I get back.