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Nicolas Lehuen
nicolas.lehuen at gmail.com
Fri Sep 9 10:52:42 EDT 2005
Oops sorry... An even better scheme is to write a module which encapsulate the access to your shared resource, and use it in your published pages (NOT manipulate the mutex directly from your published pages). This will be a lot less error prone. Regards, Nicolas 2005/9/9, Nicolas Lehuen <nicolas.lehuen at gmail.com>: > An even better scheme is to write a > > 2005/9/9, Nicolas Lehuen <nicolas.lehuen at gmail.com>: > > This is a pretty simple Python error. What you want to write is : > > > > import tconstants > > tconstants.mutex.acquire() > > > > or : > > > > from tconstants import mutex > > mutex.acquire() > > > > but NOT : > > import tconstants > > mutex.acquire() # mutex is not defined here, it is defined in the > > tconstants module... > > > > Regards, > > Nicolas > > > > 2005/9/9, John Simeone <jsimeone at inplex.com>: > > > Nicolas Lehuen wrote: > > > > > > 2005/9/8, Graham Dumpleton <grahamd at dscpl.com.au>: > > > > > > > > > On 09/09/2005, at 2:23 AM, John Simeone wrote: > > > > > > > > > > > > Hello to everyone. > > > > > > I am responsible for a project using Apache 2.0 with mod_python in a > > > Win2k environment, the choice of OS being dictated by the fact that > > > the purpose of the server is to supply access to a proprietary, > > > supplier written Windows program to our user base via the web. > > > > > > That program is single threaded and provides for only 1 user at a > > > time. Access to the program in Python is through win32com. > > > > > > I am using a mod_python.publisher handler. > > > > > > All the http requests come through a single proxy server with a static > > > address but not all are from browser clients. Some are originating > > > from perl programs but all requests are directed to a single request > > > handler. > > > > > > Can anyone suggest a method to control access to this single user > > > resource. In a non-web programming environment, I'd just use a mutex > > > semaphore to co-ordinate access among the threads but I am too much of > > > newbie with mod_python and Apache to implement a workable solution so > > > far. > > > > > > What mechanism can I use to create a shared resource that I can lock > > > and have other requests wait until the resource is unlocked? > > > > > > When using mod_python under Win32 platform, there is effectively only > > > one process and requests are handled in separate threads. Because of > > > this, you should be able to mediate access to the shared resource > > > through a normal thread mutual exclusion locking mechanism just as > > > easily as you would in a non web environment. > > > > > > Graham > > > > > > That is to say : > > > > > > import threading > > > > > > # "R" stand for Re-entrant, i.e. a thread can acquire the lock multiple > > > times > > > # make sure that the lock is instantiated only once, for example by > > > putting it in > > > # a module which your published code imports. > > > lock = threading.RLock() > > > > > > lock.acquire() > > > try: > > > # access the shared resource > > > finally: > > > lock.release() > > > > > > See the documentation of the threading module for more information. > > > > > > Regards, > > > Nicolas > > > > > > > > > > > > Thanks to Graham and Nicolas for their prompt responses. > > > > > > I followed Nicolas' counsel and created a file 'tconstants.py' : > > > > > > import threading > > > mutex = threading.RLock() > > > > > > included an 'import' into my publisher handler and wrapped the access to > > > the single resource with 'mutex.acquire()' and mutex.release(). When I got > > > an error regarding the unavailability of the mutex global, I ran the > > > following test in IDLE: > > > > > > import threading > > > import tconstants > > > def setmutex(): > > > mutex.acquire() > > > return > > > setmutex() > > > > > > and received the same error: "global name 'mutex' is not defined." > > > > > > I ran the threading demo to verify there wasn't a problem with the thread > > > module in my copy of Python 2.3. It ran fine. > > > > > > The only way I could get this test to work was to alter the code to define > > > the mutex not in the imported tconstants but in the code directly: > > > > > > import threading > > > mutex = threading.RLock() > > > def setmutex(): > > > mutex.acquire() > > > return > > > setmutex() > > > mutex.release() > > > > > > Will defining the mutex this way cause problems in proper threading control > > > for mod_python in its interaction with Apache? > > > > > > Regards, > > > > > > John > > > > > > > > > > > > _______________________________________________ > > > Mod_python mailing list > > > Mod_python at modpython.org > > > http://mailman.modpython.org/mailman/listinfo/mod_python > > > > > > > > > > > >
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