MemCachier Ruby & Facebook Example App

This is an example Ruby app that uses MemCachier to cache data from the Facebook Graph API. This example is written using the Sinatra web framework. It's currently running here on Heroku using MemCachier on Heroku.

Deploy to Heroku

You can deploy this app yourself to Heroku to play with.

Setup MemCachier

Setting up MemCachier to work in Ruby is very easy. You need to make changes to Gemfile, and any app code that you want cached. These changes are covered in detail below.

Gemfile

MemCachier has been tested with the dalli memcache client. Add the following Gem to your Gemfile:

gem 'memcachier'
gem 'dalli'

Then run bundle install as usual.

Note that the memcachier gem simply sets the appropriate environment variables for Dalli. You can also do this manually in your app.rb file if you prefer, before initializing Dalli:

ENV["MEMCACHE_SERVERS"] = ENV["MEMCACHIER_SERVERS"]
ENV["MEMCACHE_USERNAME"] = ENV["MEMCACHIER_USERNAME"]
ENV["MEMCACHE_PASSWORD"] = ENV["MEMCACHIER_PASSWORD"]

Alternatively, you can pass these options to set :cache (also in app.rb):

set :cache, Dalli::Client.new(ENV["MEMCACHIER_SERVERS"],
                  {:username => ENV["MEMCACHIER_USERNAME"],
                   :password => ENV["MEMCACHIER_PASSWORD"]}

Sinatra setup

Ensure that the following configuration option is set in your Sinatra web app at the start.

set :cache, Dalli::Client.new

Using MemCachier

We can use MemCachier to cache the list of friends a user has. Normally we have to query Facebook for this information which is slow.

# Retrieve friends list from MemCachier if possible.
def get_friends
  # cache using session id as the key. May want to use a more permanent key
  # that is meaningful across sessions.
  @friends ||= settings.cache.fetch("#{session[:at]}:friends") do
    # CACHE MISS -- so hit fb graph api and then store result in cache.
    @graph = Koala::Facebook::API.new(access_token)
    friends = @graph.fql_query("SELECT uid, name, current_location FROM user WHERE uid in (SELECT uid2 FROM friend WHERE uid1 = me())")
    settings.cache.set("#{session[:at]}:friends", friends, 600) # cache for 10 minutes
    friends
  end
end

Deploying example

Below are steps for getting the example running in its current state. If you run into any problems you can follow the more extensive Heroku guide for running Facebook web apps locally and on Heroku.

Run locally

1. Install dependencies:

   $ bundle install

2. Create an app on Facebook. Select 'Website' for how the app will interact with Facebook and set the 'Site URL' to be 'http://127.0.0.1:5000/'.

3. Copy the App ID and Secret from the Facebook app settings page into your .env:

   echo FACEBOOK_APP_ID=12345 >> .env
   echo FACEBOOK_SECRET=abcde >> .env

4. Launch the app with Foreman.

   foreman start

Deploy to Heroku via Facebook integration

The easiest way to deploy a completely new app to Facebook using Heroku is to follow the Heroku guide.

To deploy this app to Facebook:

1. Create a new Facebook application (different from the one used for local development). On the 'Create New App' dialog box at the start, select the option for 'Web Hosting' with Heorku. For the application type, select Ruby.

2. This will create a new Heroku application that is setup with Facebook correctly. Clone this new application from Heroku to you local machine.

3. Replace the existing template application that Heroku provides with the code from this repository.

4. Commit the change and deploy to Heroku.

Get involved!

We are happy to receive bug reports, fixes, documentation enhancements, and other improvements.

Please report bugs via the github issue tracker.

Master git repository:

• git clone git://github.com/memcachier/examples-sinatra.git

Licensing

This library is BSD-licensed.