Quick script to migrate heroku apps to the new free individual postgres DBs

heroku_db_migrate.rb

## README
# This is a quick script I hacked out to migrate all my heroku apps
# to the new free individual postgres DBs. To use it:
#  - install the heroku gem if you don't already have it
#  - set the value of IGNORE_OTHERS_APPS to true if you only want to
#    run the script against apps you've created yourself
#  - add any apps you want to ignore because they don't use PostgreSQL
#    (or for any other reason) to the IGNORE_LIST

## CAVEAT!!
#  - USE AT YOUR OWN RISK!! This works for me, but it may not work for you!
#  - I don't remove the SHARED_DATABASE at the end of the process in
#    case you want to rollback, so you'll need to delete it yourself once
#    you're happy everything worked
#    	heroku addons:remove shared-database
#  - if everything goes south you can just try again, but you'll have to make
#    sure that you set the shared database back to be primary by running
#       heroku pg:promote SHARED_DATABASE --app <app_name>

## N.B.
# If you do this before Aug 9th then you get:
#  - an extra 4000 lines for your DB if on the dev plan
#  - $20 credit if on basic or production plan
#
# More info at: https://devcenter.heroku.com/articles/migrating-from-shared-database-to-heroku-postgres

## OPTIONS
IGNORE_OTHERS_APPS = true
IGNORE_LIST        = [ ]

class HerokuDBMigrator
  def initialize(app_name)
    @app_name = app_name
  end

  def run
    maintenance :on
    add_required_addons
    transfer
  rescue Exception => e
    p e
  ensure
    maintenance :off
  end

  private

  def add_required_addons
    add "heroku-postgresql:dev"
    add "pgbackups"
  end

  def add(addon)
    unless installed?(addon)
      puts "adding #{addon}"
      heroku "addons:add #{addon}"
    end
  end

  def installed?(addon)
    @addons ||= heroku('addons').split(/\n/).map{|a| a.split(' => ').first}

    not @addons.select {|a| a.include?(addon)}.empty?
  end

  def transfer
    backup_existing_db
    setup_new_db
  end

  def maintenance(state)
    heroku "maintenance:#{state}"
    puts "maintenance #{state}"
  end

  def backup_existing_db
    puts "backing up existing DB"
    heroku "pgbackups:capture --expire"
  end

  def setup_new_db
    db_name = heroku("config").match(/(HEROKU_POSTGRESQL_.*)_URL/)[1]

    puts "setting up #{db_name}"
    heroku "pgbackups:restore #{db_name} --confirm #{@app_name}"

    puts "making #{db_name} primary"
    heroku "pg:promote #{db_name}"
  end

  def heroku(command)
    `heroku #{command} --app #{@app_name}`
  end
end

apps = `heroku apps`.split(/\n/)
apps.reject! {|app| app =~ /\s+/} if IGNORE_OTHERS_APPS
apps -= IGNORE_LIST

apps.each do |app|
  puts "\nTransferring app: #{app}"
  HerokuDBMigrator.new(app).run
  puts
end