Environment variables in Rails

When you see configuration examples in a gem’s README like this:

You can find this real example in the README of the awesome assets_sync gem.

AssetSync.configure do |config|
  config.fog_provider = 'AWS'
  config.fog_directory = ENV['FOG_DIRECTORY']
  config.aws_access_key_id = ENV['AWS_ACCESS_KEY_ID']
  config.aws_secret_access_key = ENV['AWS_SECRET_ACCESS_KEY']

  # Don't delete files from the store
  # config.existing_remote_files = "keep"
  #
  # Increase upload performance by configuring your region
  # config.fog_region = 'eu-west-1'
  #
  # Automatically replace files with their equivalent gzip compressed version
  # config.gzip_compression = true
  #
  # Use the Rails generated 'manifest.yml' file to produce the list of files to
  # upload instead of searching the assets directory.
  # config.manifest = true
  #
  # Fail silently.  Useful for environments such as Heroku
  # config.fail_silently = true
end

what do you think they are? Where should you define ENV['FOG_DIRECTORY']? Should you define it in a shell script (like ~/.bashrc, ~/.bash_profile, ~/.profile and so on), or maybe in /etc/environment? If you think so, I have to disappoint you — you are wrong!

Challenge

Let’s define the FOG_DIRECTORY variable in the ~/.bashrc file:

Note that if ~/.bashrc includes the line [ -z "$PS1" ] && return or an equivalent, you have to define the variables above it.

export FOG_DIRECTORY=my-bucket-name

Then restart the shell and start the Rails application. You will see that the application is configured correctly. You enjoy it and plan to deploy the application to production on the VPS or VDS in the same way, and everything will work there… until the first reboot. Why is ENV['FOG_DIRECTORY'] nil after the server reboots? The answer is simple — nginx or another web server (I don’t know which one you use, but I prefer nginx) starts before ~/.bashrc and even /etc/environment are evaluated.

If you use assets_sync to upload your assets to the cloud, you can get this error during deployment with capistrano:

AssetSync: using default configuration from built-in initializer
rake aborted!
Fog provider can't be blank, Fog directory can't be blank

Tasks: TOP => assets:precompile:nondigest
(See full trace by running task with --trace)

So we have to look for another way to define these variables.

Solution

Considering the problem above, there is a reasonable question: what are these variables in the config, and what should we do? How should we define them?

While surfing the internet, I’ve found a good article that explains ways to achieve our goals.

I will describe the option I prefer because I think it is the simplest and faster than the others.

Insert these lines of code into config/application.rb after the line config.assets.version = '1.0':

config.before_configuration do
  env_file = File.join(Rails.root, 'config', 'local_env.yml')
  YAML.load(File.open(env_file)).each do |key, value|
    ENV[key.to_s] = value
  end if File.exists?(env_file)
end

Now you have to create a yml file in the config folder and add it to .gitignore if you need to define these variables locally. Here is an example of config/local_env.yml:

These key values are not real, so it doesn’t make sense to paste them into your configuration files.

FOG_PROVIDER: AWS
FOG_DIRECTORY: my-bycket-name
AWS_ACCESS_KEY_ID: ASFAWFSFDGSDEQWEFGD
AWS_SECRET_ACCESS_KEY: Afsdgd35gSFsdgSDF46GDSG4ghdf356
FOG_REGION: eu-west-1

And finally, if we deploy the application with Capistrano, we have to do it properly. We should put local_env.yml in the Capistrano shared folder on the server and change config/deploy.rb like this:

before 'deploy:assets:precompile', :symlink_config_files

desc "Link shared files"
task :symlink_config_files do
  symlinks = {
    "#{shared_path}/config/database.yml" => "#{release_path}/config/database.yml",
    "#{shared_path}/config/local_env.yml" => "#{release_path}/config/local_env.yml"
  }
  run symlinks.map{|from, to| "ln -nfs #{from} #{to}"}.join(" && ")
end

Here, it is assumed that local_env.yml exists in the {shared_path}/config/ folder on the server. Note that I’ve done the same thing with my database.yml config (by the way, ignoring database.yml in your CVS is best practice too).