Capistrano::Rails

Rails specific tasks for Capistrano v3:

cap deploy:migrate
cap deploy:compile_assets

Installation

Add these Capistrano gems to your application's Gemfile using require: false:

group :development do
  gem "capistrano", "~> 3.10", require: false
  gem "capistrano-rails", "~> 1.6", require: false
end

Run the following command to install the gems:

bundle install

Then run the generator to create a basic set of configuration files:

bundle exec cap install

Usage

Require everything (bundler, rails/assets and rails/migrations):

# Capfile
require 'capistrano/rails'

Or require just what you need manually:

# Capfile
require 'capistrano/bundler' # Rails needs Bundler, right?
require 'capistrano/rails/assets'
require 'capistrano/rails/migrations'

Please note that any requires should be placed in Capfile, not in config/deploy.rb.

You can tweak some Rails-specific options in config/deploy.rb:

# If the environment differs from the stage name
set :rails_env, 'staging'

# Defaults to :db role
set :migration_role, :db

# Defaults to the primary :db server
set :migration_servers, -> { primary(fetch(:migration_role)) }

# Defaults to `db:migrate`
set :migration_command, 'db:migrate'

# Defaults to false
# Skip migration if files in db/migrate were not modified
set :conditionally_migrate, true

# Defaults to [:web]
set :assets_roles, [:web, :app]

# Defaults to 'assets'
# This should match config.assets.prefix in your rails config/application.rb
set :assets_prefix, 'prepackaged-assets'

# Defaults to ["/path/to/release_path/public/#{fetch(:assets_prefix)}/.sprockets-manifest*", "/path/to/release_path/public/#{fetch(:assets_prefix)}/manifest*.*"]
# This should match config.assets.manifest in your rails config/application.rb
set :assets_manifests, ['app/assets/config/manifest.js']

# RAILS_GROUPS env value for the assets:precompile task. Default to nil.
set :rails_assets_groups, :assets

# If you need to touch public/images, public/javascripts, and public/stylesheets on each deploy
set :normalize_asset_timestamps, %w{public/images public/javascripts public/stylesheets}

# Defaults to nil (no asset cleanup is performed)
# If you use Rails 4+ and you'd like to clean up old assets after each deploy,
# set this to the number of versions to keep
set :keep_assets, 2

Symlinks

You'll probably want to symlink Rails shared files and directories like log, tmp and public/uploads. Make sure you enable it by setting linked_dirs and linked_files options:

# deploy.rb
append :linked_dirs, 'log', 'tmp/pids', 'tmp/cache', 'tmp/sockets', 'vendor/bundle', '.bundle', 'public/system', 'public/uploads'
append :linked_files, 'config/database.yml', 'config/secrets.yml'

In capistrano < 3.5, before append was introduced, you can use fetch and push to get the same result.

Recommendations

While migrations looks like a concern of the database layer, Rails migrations are strictly related to the framework. Therefore, it's recommended to set the role to :app instead of :db like:

set :migration_role, :app

The advantage is you won't need to deploy your application to your database server, and overall a better separation of concerns.

Uploading your master.key

You can use the below configuration to upload your master.key to the server if it isn't already present.

append :linked_files, "config/master.key"

namespace :deploy do
  namespace :check do
    before :linked_files, :set_master_key do
      on roles(:app) do
        unless test("[ -f #{shared_path}/config/master.key ]")
          upload! 'config/master.key', "#{shared_path}/config/master.key"
        end
      end
    end
  end
end