Capistrano in Open Source Projects and different environments - capistrano

Question

I consider to use Capistrano to deploy my rails app on my server. Currently I'm using a script, which does all the work for me. But Capistrano looks pretty nice and I want to give it a try.
My first problem/question now is: How to use Capistrano properly in open source projects? I don't want to publish my deploy.rb for several reasons:
It contains sensible informations about my server. I don't want to publish them :)
It contains the config for MY server. For other people, which deploy that open source project to their own server, the configuration may differ. So it's pretty senseless to publish my configuration, because it's useless for other people.
Second problem/question: How do I manage different environments?
Background: On my server I provide two different environments for my application: The stable system using the current stable release branch and located under www.domain.com. And a integration environment for the develop team under dev.domain.com running the master branch.
How do I tell Capistrano to deploy the stable system or the dev system?

Answer 1

The way I handle sensitive information (passwords etc.) in Capistrano is the same way I handle them in general: I use an APP_CONFIG hash that comes from a YAML file that isn't checked into version control. This is a classic technique that's covered e.g. in RailsCast #226, or see this StackOverflow question.
There are a few things you have to do a little differently when using this approach with Capistrano:
Normally APP_CONFIG is loaded from your config/application.rb (so it happens early enough to be usable everywhere else); but Capistrano cap tasks won't load that file. But you can just load it from config/deploy.rb too; here's the top of a contrived config/deploy.rb file using an HTTP repository that requires a username/password.
require 'bundler/capistrano'
APP_CONFIG = YAML.load_file("config/app_config.yml")
set :repo_user, APP_CONFIG['repo_user']
set :repo_password, APP_CONFIG['repo_password']
set :repository, "http://#{repo_user}:#{repo_password}#hostname/repositoryname.git/"
set :scm, :git
# ...
The config/app_config.yml file is not checked into version control (put that path in your .gitignore or similar); I normally check in a config/app_config.yml.sample that shows the parameters that need to be configured:
repo_user: 'usernamehere'
repo_password: 'passwordhere'
If you're using the APP_CONFIG for your application, it probably needs to have different values on your different deploy hosts. So have your Capistrano setup make a symlink from the shared/ directory to each release after it's checked out. You want to do this early in the deploy process, because applying migrations might need a database password. So in your config/deploy.rb put this:
after 'deploy:update_code', 'deploy:symlink_app_config'
namespace :deploy do
desc "Symlinks the app_config.yml"
task :symlink_app_config, :roles => [:web, :app, :db] do
run "ln -nfs #{deploy_to}/shared/config/app_config.yml #{release_path}/config/app_config.yml"
end
end
Now, for the second part of your question (about deploying to multiple hosts), you should configure separate Capistrano "stages" for each host. You put everything that's common across all stages in your config/deploy.rb file, and then you put everything that's unique to each stage into config/deploy/[stagename].rb files. You'll have a section in config/deploy.rb that defines the stages:
# Capistrano settings
require 'bundler/capistrano'
require 'capistrano/ext/multistage'
set :stages, %w(preproduction production)
set :default_stage, 'preproduction'
(You can call the stages whatever you want; the Capistrano stage name is separate from the Rails environment name, so the stage doesn't have to be called "production".) Now when you use the cap command, insert the stage name between cap and the target name, e.g.:
$ cap preproduction deploy #deploys to the 'preproduction' environment
$ cap production deploy #deploys to the 'production' environment
$ cap deploy #deploys to whatever you defined as the default