Deploy Strategies

This article originally appeared on the "Mutterings from the Global Village Idiot" blog

If you look at the network graphs of heroku_san on github, you'll see a number of branches where the only change is the deletion of the following line from the deploy task:

• stage.migrate

When more than a few people are willing to take the effort to fork a gem just so they can delete 1 line, something smells. These forkers are using something other than Rails+ActiveRecord+SQL in their project, some were using Sinatra, others were using Rails, but with CouchDB.

The raison d'être for the heroku_san gem is to make Heroku deploys dirt simple; so, if people are making whole forks to customize the deploy task, we should make it less painful.

Enter strategies

Strategies are an object oriented programming pattern for creating pluggable execution control. HerokuSan has a new class of objects that inherit from HerokuSan::Deploy::Base. These objects control how deploys are executed for you. The Rails strategy, HerokuSan::Deploy::Rails does exactly what HerokuSan has always done:

• push to [email protected]
• call rake db:migrate
• restart

On the other hand, the Sinatra strategy, HerokuSan::Deploy::Sinatra does nothing more than the base strategy:

• push to [email protected]

You can create your own strategies and then configure HerokuSan to use it instead of its default:

Rails projects

Amend your Rakefile:

require 'heroku_san'

class MyStrategy < HerokuSan::Deploy::Base
  def deploy
    super
    # call my own code to do something unique
  end
end

HerokuSan.project = HerokuSan::Project.new(Rails.root.join("config","heroku.yml"), :deploy => MyStrategy)

Sinatra (and other Rack based apps)

Amend your Rakefile

require 'heroku_san'

class MyStrategy < HerokuSan::Deploy::Base
  def deploy
    super
    # call my own code to do something unique
  end
end

config_file = File.join(File.expand_path(File.dirname(__FILE__)), 'config', 'heroku.yml')
HerokuSan.project = HerokuSan::Project.new(config_file, :deploy => MyStrategy)

load "heroku_san/tasks.rb"