Plug.Session.MEMCACHED

This is a very simple memcached session store for Elixir's plug. I use it in conjunction with the great Phoenix Framework.

Synopsis

Add these to your project's mix.exs:

# will create a mcd connection to memcached as :memcached_sessions
def application do
  [
    ...
    applications: [
        ...
        :plug_session_memcached # <--- add this entry
    ]
  ]
end

# add dependency
defp deps do
  [
    ...
    {:plug_session_memcached, "~> 0.3.1" }, # <-- add this entry
    {:mcd, github: "EchoTeam/mcd"}          # <-- and this one 
  ]
end

You may want to alter the standard memcached host/port in your config.exs (or dev.exs or prod.exs). If no config is given, host 127.0.0.1 and port 11211 is used:

# be sure to use a binary for the host the underlying memcached connector is written in Erlang)
# server: [ <host_binary>, <port_integer> ]
config :plug_session_memcached,
  server: [ '127.0.0.1', 11211 ]

Be sure to manually include :mcd as hex won't fetch github dependencies automatically for you. At some point I might switch to tsharju's :memcache_client which should do the same.

Then use the plug

plug Plug.Session,
  store: :memcached,
  key: "_my_app_key", # use a proper value 
  table: :memcached_sessions, # <-- this on is hard coded into the plug
  signing_salt: "123456",   # use a proper value
  encryption_salt: "654321" # use a proper value

In phoenix (version 1.0 and above), add the lines above to your lib/enpoint.ex

TODO

[x] Add tests: create a small service with Cowboy answering http request with some session data in them. [x] Let memcached server/port be configurable from config.exs [ ] Add proper docs

Motivation: Why Memcached when there's an ETS or Cookie store?

A short discussion: I am probably wrong.

Cookies

While it's so great and simple to store session data in the cookie itself, it has some downsides:

Even when the cookie is encrypted and signed, there is still some information about the size of information stored in it.

Apart from changing your session key there's no easy way to invalidate a certain session cookie. For example: A user logs in and you assign the value "user_id",