Environment variables in Rails

Andrei Kaleshka

15 Feb 2013

When you see configuration examples in gems README like this:

This real example you can find in the README of awesome gem assets_sync.

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

Challenge

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

Pay attention if ~/.bashrc includes line [ -z "$PS1" ] && return or equal you have to define variables above it

export FOG_DIRECTORY=my-bucket-name

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

If you use assets_sync to upload your assets to the cloud you can have this error during deployment with capistrano](https://github.com/capistrano/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 looking for another way how to define these variables.

Solution

Considering the problem above there is a reasonable question - what are these variables in config at all and what to do? How should we define these variables?

During surfing the Internet I’ve found a good article which explains cases how to achieve our goals.

I will describe here the case which I prefer because I think it is the simplest and faster than others.

Insert these lines of code to the config/application.rb after 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 yml file in config folder and add it to .gitignore if you have to define these variables locally. Example of config/local_env.yml:

Key values are not real, so it doesn’t make sense to paste them in 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 application with Capistrano we have to deploy it properly. We should put local_env.yml to 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 is existed in the {shared_path}/config/ folder on the server. Check out here that I’ve done the same things with my database.yml config (by the way ignore the database.yml in your CVS it’s the best practice too).