Add cookbook article for using MongoDB to store session data

Author: stevenmusumeche

cookbook/configuration/mongodb_session_storage.rst

@@ -0,0 +1,54 @@
+How to Use MongoDbSessionHandler to Store Sessions in a MongoDB Database
+========================================================================
+
+The default Symfony session storage writes the session information to files.
+Some medium to large websites use a NoSQL database called MongoDB to store the
+session values instead of files, because databases are easier to use and scale
+in a multi-webserver environment.
+
+Symfony has a built-in solution for NoSQL database session storage called
+:class:`Symfony\\Component\\HttpFoundation\\Session\\Storage\\Handler\\MongoDbSessionHandler`.
+MongoDB is an open-source document database that provides high performance,
+high availability, and automatic scaling. This article assumes that you have
+already `installed and configured a MongoDB server`_. To use it, you just
+need to change/add some parameters in the main configuration file:
+
+.. configuration-block::
+
+    .. code-block:: yaml
+
+        # app/config/config.yml
+        framework:
+            session:
+                # ...
+                handler_id:  session.handler.mongo
+                cookie_lifetime: 2592000 # optional, it is set to 30 days here
+                gc_maxlifetime: 2592000 # optional, it is set to 30 days here
+
+        parameters:
+            # ...
+            mongo.session.options:
+                database: session_db # your MongoDB database name
+                collection: session  # your MongoDB collection name
+            mongodb_host: 1.2.3.4 # your MongoDB server's IP
+            mongodb_username: my_username
+            mongodb_password: my_password
+
+        services:
+            # ...
+            mongo_client:
+                class: MongoClient
+                # if using a username and password
+                arguments: [mongodb://%mongodb_username%:%mongodb_password%@%mongodb_host%:27017]
+                # if not using a username and password
+                arguments: [mongodb://%mongodb_host%:27017]
+            session.handler.mongo:
+                class: Symfony\Component\HttpFoundation\Session\Storage\Handler\MongoDbSessionHandler
+                arguments: [@mongo_client, %mongo.session.options%]
+
+Setting Up the MongoDB Collection
+---------------------------------
+Because MongoDB uses dynamic collection schemas, you do not need to do anything to initialize your
+session collection.
+
+.. _installed and configured a MongoDB server: http://docs.mongodb.org/manual/installation/