MemCachier Rack::Cache Example App

This is an example Rails app that uses Rack::Cache with MemCachier for caching assets. This example is written with Rails 4.0, but also runs fine with Rails 3.2.

Please follow this tutorial for getting started with Rack::Cache.

You can view a working version of this app here that uses MemCachier on Heroku. Running this app on your local machine in development will work as well, although then you won't be using MemCachier -- you'll be using a local dummy cache. MemCachier is currently only available with various cloud providers.

Deploy to Heroku

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

Running

To run this rails app, first install the needed gems.

$ gem install bundler
$ bundle install

Then create a database and run your migrations.

$ bundle exec rake db:create
$ bundle exec rake db:migrate

Then create your production database and precompile your assets.

$ bundle exec rake db:create RAILS_ENV=production
$ bundle exec rake assets:precompile

Now start memcached locally.

$ memcached

Next, start your server. You'll want to run in production so that caching is enabled.

$ rails s -e production

Visit http://localhost:3000 and view your logs, you should see some cache entries

cache: [GET /assets/application-193197163ac0c1601c69cbdaf22f6ce6.css] miss, store
cache: [GET /assets/application-bf044948e75c7535c35baf4b42604116.js] miss, store
cache: [GET /assets/rails-782b548cc1ba7f898cdad2d9eb8420d2.png] miss, store

Refresh the page and you should see that those entries can be pulled fresh from cache

cache: [GET /assets/application-193197163ac0c1601c69cbdaf22f6ce6.css] fresh
cache: [GET /assets/application-bf044948e75c7535c35baf4b42604116.js] fresh
cache: [GET /assets/rails-782b548cc1ba7f898cdad2d9eb8420d2.png] fresh

When you modify a file such as app/assets/stylsheets/application.css and run rake assets:precompile and then start and stop your server, you should see that there is now a new digest for the file and it must be stored in cache again.

Setup MemCachier

Setting up MemCachier to work in Rails is very easy. You need to make changes to Gemfile, production.rb, 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 production.rb file if you prefer:

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 config.cache_store (also in production.rb):

config.cache_store = :mem_cache_store, ENV["MEMCACHIER_SERVERS"].split(','),
                    {:username => ENV["MEMCACHIER_USERNAME"],
                     :password => ENV["MEMCACHIER_PASSWORD"]}

production.rb

Ensure that the following configuration option is set in production.rb:

# Configure rails caching (action, fragment)
config.cache_store = :mem_cache_store

# Configure Rack::Cache (rack middleware, whole page / static assets)
client = Dalli::Client.new(ENV["MEMCACHIER_SERVERS"],
                           :value_max_bytes => 10485760)
config.action_dispatch.rack_cache = {
  :metastore    => client,
  :entitystore  => client
}
config.static_cache_control = "public, max-age=2592000"

Rack::Cache

For detailed documentation see the Rack::Cache homepage.

Rack::Cache Metastore

The metastore holds metadata about the objects in cache. Metastore entries are small and accessed frequently. It makes alot of sense to put this data in a fast light datastore such as Memcache

Rack::Cache Entitystore

The entity store is where the objects get cached. Entity store objects are typically large and accessed infrequently. For that reason it might make sense to store them on disk rather than to take up a large amount of room in Memcache.

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-rack-cache.git

Licensing

This library is BSD-licensed.

Licensed under MIT License Copyright (c) 2012 Schneems. See LICENSE for further details.