My web application works fine in development environment, but on production server gives off:
504 Gateway Time-out The server didn't respond in time.
Edit: I have traced the problem to a
session_start() call - it never completes and ends in a 504 error above. What could cause this?
Both servers are running Linux, although of course they are not perfect clones of each other. There are many other php apps running on the same server with no issues, the production server is not overloaded in any way, and hardware wise, the production server is much better in specs than the development one. I checked out php error log and do not see anything other than
[22-Aug-2011 09:38:01] PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/pdo_sqlite.so' - /usr/lib64/php/modules/pdo_sqlite.so: undefined symbol: php_pdo_register_driver in Unknown on line 0
Which is something I see all the time even if it's working fine, and I generally don't care about this error as I'm not using sqlite.
Where else can I see what's going on and what to do to fix it?
While I could not figure out what caused the initial problem, it turned out that the problem was not occurring when using a different web browser. After restarting the problematic browser instance (it was Firefox, btw) the issue went away completely. I'm still puzzled how a browser could cause a server to throw 504 error.