.. _pymongo-and-mod_wsgi: PyMongo and mod_wsgi ==================== To run your application under `mod_wsgi `_, follow these guidelines: * Run ``mod_wsgi`` in daemon mode with the ``WSGIDaemonProcess`` directive. * Assign each application to a separate daemon with ``WSGIProcessGroup``. * Use ``WSGIApplicationGroup %{GLOBAL}`` to ensure your application is running in the daemon's main Python interpreter, not a sub interpreter. For example, this ``mod_wsgi`` configuration ensures an application runs in the main interpreter:: WSGIDaemonProcess my_process WSGIScriptAlias /my_app /path/to/app.wsgi WSGIProcessGroup my_process WSGIApplicationGroup %{GLOBAL} If you have multiple applications that use PyMongo, put each in a separate daemon, still in the global application group:: WSGIDaemonProcess my_process WSGIScriptAlias /my_app /path/to/app.wsgi WSGIProcessGroup my_process WSGIDaemonProcess my_other_process WSGIScriptAlias /my_other_app /path/to/other_app.wsgi WSGIProcessGroup my_other_process WSGIApplicationGroup %{GLOBAL} Background: ``mod_wsgi`` can run in "embedded" mode when only WSGIScriptAlias is set, or "daemon" mode with WSGIDaemonProcess. In daemon mode, ``mod_wsgi`` can run your application in the Python main interpreter, or in sub interpreters. The correct way to run a PyMongo application is in daemon mode, using the main interpreter. Python C extensions in general have issues running in multiple Python sub interpreters. These difficulties are explained in the documentation for `Py_NewInterpreter `_ and in the `Multiple Python Sub Interpreters `_ section of the ``mod_wsgi`` documentation. Beginning with PyMongo 2.7, the C extension for BSON detects when it is running in a sub interpreter and activates a workaround, which adds a small cost to BSON decoding. To avoid this cost, use ``WSGIApplicationGroup %{GLOBAL}`` to ensure your application runs in the main interpreter. Since your program runs in the main interpreter it should not share its process with any other applications, lest they interfere with each other's state. Each application should have its own daemon process, as shown in the example above.