mod_wsgi and Django app periodically hang

I've got a large Django app. It has two Apache virtual hosts pointing to different setting开发者_Python百科s files, so part of the application is accessible via one URL, and part via another. The Django app uses virtualenv.

mod_wsgi is configured to run in daemon mode with the following in Apache's VirtualHost block:

# domain 1:
WSGIDaemonProcess fc processes=5 threads=5 display-name=%{GROUP} \
    user=nobody group=nobody
WSGIScriptAlias / /var/www/python/mine/apache/my.wsgi \
    process-group=fc application-group=%{GROUP}


# different apache.conf file for domain 2:
WSGIDaemonProcess fm processes=5 threads=5 display-name=%{GROUP} \
    user=nobody group=nobody

WSGIScriptAlias / /var/www/python/mine/apache/other.wsgi \
    process-group=fm application-group=%{GROUP}

Every now and again while using the sites, a request will hang. It never completes. I have to use the browser's 'refresh' button to reload the page, and then the request normally works.

Apache itself runs in prefork mode and MaxRequestsPerChild is set to 0 because I've read that could be a problem. This happens often enough for it to be a potential problem - every 100 requests perhaps, something like that.

Has anyone got any idea why this is happening?

Thanks

That should be 'application-group=%{GLOBAL}' for WSGIDaemonProcess options, not '%{GROUP}'. The '%{GLOBAL}' is special and means the main Python interpreter. Using the main interpreter often gets around problems with third party C extension modules for Python which don't work in sub interpreters, including experiencing deadlocks. The '%{GROUP}' value is only relevant to the 'display-name' option.