1.. _pymongo-and-mod_wsgi: 2 3PyMongo and mod_wsgi 4==================== 5 6To run your application under `mod_wsgi <http://code.google.com/p/modwsgi/>`_, 7follow these guidelines: 8 9* Run ``mod_wsgi`` in daemon mode with the ``WSGIDaemonProcess`` directive. 10* Assign each application to a separate daemon with ``WSGIProcessGroup``. 11* Use ``WSGIApplicationGroup %{GLOBAL}`` to ensure your application is running 12 in the daemon's main Python interpreter, not a sub interpreter. 13 14For example, this ``mod_wsgi`` configuration ensures an application runs in the 15main interpreter:: 16 17 <VirtualHost *> 18 WSGIDaemonProcess my_process 19 WSGIScriptAlias /my_app /path/to/app.wsgi 20 WSGIProcessGroup my_process 21 WSGIApplicationGroup %{GLOBAL} 22 </VirtualHost> 23 24If you have multiple applications that use PyMongo, put each in a separate 25daemon, still in the global application group:: 26 27 <VirtualHost *> 28 WSGIDaemonProcess my_process 29 WSGIScriptAlias /my_app /path/to/app.wsgi 30 <Location /my_app> 31 WSGIProcessGroup my_process 32 </Location> 33 34 WSGIDaemonProcess my_other_process 35 WSGIScriptAlias /my_other_app /path/to/other_app.wsgi 36 <Location /my_other_app> 37 WSGIProcessGroup my_other_process 38 </Location> 39 40 WSGIApplicationGroup %{GLOBAL} 41 </VirtualHost> 42 43Background: ``mod_wsgi`` can run in "embedded" mode when only WSGIScriptAlias 44is set, or "daemon" mode with WSGIDaemonProcess. In daemon mode, ``mod_wsgi`` 45can run your application in the Python main interpreter, or in sub interpreters. 46The correct way to run a PyMongo application is in daemon mode, using the main 47interpreter. 48 49Python C extensions in general have issues running in multiple 50Python sub interpreters. These difficulties are explained in the documentation for 51`Py_NewInterpreter <http://docs.python.org/2/c-api/init.html#Py_NewInterpreter>`_ 52and in the `Multiple Python Sub Interpreters 53<https://code.google.com/p/modwsgi/wiki/ApplicationIssues#Multiple_Python_Sub_Interpreters>`_ 54section of the ``mod_wsgi`` documentation. 55 56Beginning with PyMongo 2.7, the C extension for BSON detects when it is running 57in a sub interpreter and activates a workaround, which adds a small cost to 58BSON decoding. To avoid this cost, use ``WSGIApplicationGroup %{GLOBAL}`` to 59ensure your application runs in the main interpreter. 60 61Since your program runs in the main interpreter it should not share its 62process with any other applications, lest they interfere with each other's 63state. Each application should have its own daemon process, as shown in the 64example above. 65