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+.. _contrib-modules:
+
+Contrib Modules
+===============
+
+These modules implement various extra features, that may not be ready for
+prime time.
+
+.. _contrib-pyopenssl:
+
+SNI-support for Python 2
+------------------------
+
+.. automodule:: urllib3.contrib.pyopenssl
+
+
+.. _gae:
+
+Google App Engine 
+-----------------
+
+The :mod:`urllib3.contrib.appengine` module provides a pool manager that
+uses Google App Engine's `URLFetch Service <https://cloud.google.com/appengine/docs/python/urlfetch>`_.
+
+Example usage::
+
+    from urllib3 import PoolManager
+    from urllib3.contrib.appengine import AppEngineManager, is_appengine_sandbox
+
+    # This substitution will be done automagically once appengine code
+    # graduates from the contrib module.
+    if is_appengine_sandbox():
+        # AppEngineManager uses AppEngine's URLFetch API behind the scenes
+        http = AppEngineManager()
+    else:
+        # PoolManager uses a socket-level API behind the scenes
+        http = PoolManager()
+
+    # The client API should be consistent across managers, though some features are not available
+    # in URLFetch and you'll get warnings when you try to use them (like granular timeouts).
+    r = http.request('GET', 'https://google.com/')
+
+
+There are `limitations <https://cloud.google.com/appengine/docs/python/urlfetch/#Python_Quotas_and_limits>`_ to the URLFetch service and it may not be the best choice for your application. App Engine provides three options for urllib3 users:
+
+1. You can use :class:`AppEngineManager` with URLFetch. URLFetch is cost-effective in many circumstances as long as your usage is within the limitations.
+2. You can use a normal :class:`PoolManager` by enabling sockets. Sockets also have `limitations and restrictions <https://cloud.google.com/appengine/docs/python/sockets/#limitations-and-restrictions>`_ and have a lower free quota than URLFetch. To use sockets, be sure to specify the following in your ``app.yaml``::
+    
+    env_variables:
+        GAE_USE_SOCKETS_HTTPLIB : 'true'
+
+3. If you are using `Managed VMs <https://cloud.google.com/appengine/docs/managed-vms/>`_, you can use the standard :class:`PoolManager` without any configuration or special environment variables.