Merge pull request #64 from patriciomacadden/dalli

Add a recipe about using Dalli for sessions stored in memcached

middleware/share_session_with_memcached.md

@@ -0,0 +1,43 @@
+# How to share a session with Memcached?
+
+Suppose that you are developing a Sinatra app that will be deployed to multiple
+server instances and must be seen as a single application (it must be balanced
+with nginx, for instance). You need a mechanism for sharing user sessions
+between all the application instances. To accomplish this task, we'll use
+memcached for sharing the session and [Dalli](https://github.com/mperham/dalli)
+as the memcached client.
+
+First, add `dalli` to your `Gemfile`:
+
+```ruby
+gem 'dalli'
+```
+
+Then, add the `Rack::Session::Dalli` middleware:
+
+```ruby
+configure do
+  use Rack::Session::Dalli, cache: Dalli::Client.new
+end
+```
+
+`Dalli::Client` defaults the memcache server url to `localhost:11211`. If you
+need to use another server, you must configure it yourself.
+
+See a full example configuring the memcache server and the session namespace:
+
+```ruby
+configure do
+  use Rack::Session::Dalli,
+    memcache_server: 'example.com:11211',
+    namespace: 'other.namespace'
+    cache: Dalli::Client.new
+end
+```
+
+## More Info
+
+Refer to [Rack::Session](http://rack.rubyforge.org/doc/Rack/Session.html)
+documentation to know more about rack sessions.
+Refer to [Dalli](https://github.com/mperham/dalli) documentation to know more
+about Rack::Session::Dalli.