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Gregory (Grisha) Trubetskoy
grisha at modpython.org
Fri May 14 13:32:25 EDT 2004
I think Byron was referring to classic definition of a "race condition", which is "whoever gets there first will determine the outcome of events" (more info here http://en.wikipedia.org/wiki/Race_condition). I think the racing you're referring to is called an infinite loop or a stale lock. The former is an indiciation of a problem with your code, and you should see a process on your server consuming a lot of CPU time when this happens. The latter could happen if httpd crashed before having a chance to release the lock. If httpd crashed, you would see something in your error logs like 'exited on signal 11'. Another possibility (of a stale lock) is that somehow mod_python fails to release the lock, i.e. the cleanup isn't executing, but in my experience cleanups are 100% reliable, I've never seen one not executing. So I would try to work towards figuring out conclusively what the issue is narrowing it down to one of the possibilities I listed, from there we can start solving the problem (or you'll solve it yourself in the process). Grisha On Fri, 14 May 2004, SAiello at Jentoo.com wrote: > On Friday 14 May 2004 09:56 am, Gregory (Grisha) Trubetskoy wrote: > > With session locking on (which would be true in the code above), once one > > process reaches 2, no other process will be able to get past 1 until the > > first request is over. So there is no race condition, unless I'm missing > > something. > > With that 1st code sample of mine, if racing = my broweser waiting forever for > a response from the server, because my code was stuck in the while loop. Then > I was somehow racing. I think it could of been my code though, it wasn't the > best of examples. > > Since my original post, I have since updated how I manage multiple > simultaneous sessions. If you like I can create a test script using the first > one to test for racing to confirm that I was. > > Since I am not very knowledgeable on the dynamics of Apache, I can only guess > why I was racing. But when I was clicking wildly at the mod_python page, I > had top open on the server. Sometimes I would see an apache process marked as > defunct. Could it be this process, incremented the session variable, then it > went defunct, hence never decrementing the session var ? > > Server Specs: > Gentoo distribution of GNU/Linux, kernel 2.6.4 > Apache 2.0.49 with berkdb, gdbm, & ldap compiled in. > mod_python 3.1.3 > > > _______________________________________________ > Mod_python mailing list > Mod_python at modpython.org > http://mailman.modpython.org/mailman/listinfo/mod_python >
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