Heroku

The default configuration won't work out of the box for Heroku, because

• Heroku doesn't allow saving files to the filesystem (although it does use tempfiles)
• If on Heroku Aspen/Bamboo stacks, we won't need Rack::Cache, because it already uses the caching proxy Varnish, which we can make use of. We will still need it on Heroku Cedar, however, as it doesn't include Varnish.

Instead of the normal FileDataStore, we can use the S3DataStore.

Assuming you have an S3 account set up...

Gem dependencies:

- fog
- dragonfly

Initializer (e.g. config/initializers/dragonfly.rb in Rails):

require 'dragonfly'
app = Dragonfly[:images]

app.configure_with(:imagemagick)
app.configure_with(:rails)
if Rails.env.production?
  app.configure do |c|
    c.datastore = Dragonfly::DataStorage::S3DataStore.new(
      :bucket_name => 'my-bucket-name',
      :access_key_id => ENV['S3_KEY'],
      :secret_access_key => ENV['S3_SECRET']
    )
  end
end

app.define_macro(ActiveRecord::Base, :image_accessor)

The datastore remains as the FileDataStore for non-production environments.

application.rb if using with Rails:

config.middleware.insert 1, 'Dragonfly::Middleware', :images

We don't store the S3 access key and secret in the repository, rather we use Heroku's config variables using the command line (we only have to do this once).

From your app's directory:

heroku config:add S3_KEY=XXXXXXXXX S3_SECRET=XXXXXXXXXX

Replace 'XXXXXXXXX' with your access key and secret.

NOTE: HEROKU'S VARNISH CACHE IS CLEARED EVERY TIME YOU DEPLOY!!! (DOESN'T APPLY TO CEDAR STACK)

If this is an issue, you may want to look into storing thumbnails on S3 (see ServingRemotely), or maybe generating thumbnails on upload (see Models), or maybe an after-deploy hook for hitting specific Dragonfly urls you want to cache, etc. It won't be a problem for most sites though.