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
    raise "No app_name set" if @app_name.nil? or @app_name == ""

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

  private

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

  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 get_addons
    heroku('addons').split(/\n/).map{|a| a.split(' => ').first}.compact
  end

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

  def transfer
    backup_existing_db
    setup_new_db
  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

Yeah I tested that one as it seemed most obvious culprit (although I'd have thought that no add-ons in heroku would just return an empty array which means the #include? in the select would never get called). I thought that what was happening was that the second split on ' => ' was returning an array with nil as the first element, but I couldn't get any output for 'heroku addons' to produce that result. I figured that by compacting the array (not uniq as I first did in my hungover state :D) would remove any nils and therefore remove errors so I just went with that.

What _was_quite interesting though (for a given vaue of interesting) was that the output you pasted showed that no app_name was being passed in to the HerokuDBMigrator. That would cause all calls to be made with --app at the end with no app. So I reckon I must be incorrectly parsing the error message returned from that. So if you can figure out how it managed to get a nil/blank app name, you'll be on the right path ;)

Turns out that's exactly what it was. If there you do heroku addons --app you get the usage message returned, which in turn generates an array with nils in it. I've left the compact in, but I've also changed the run method to raise an error before starting if no app_name is set.

Thanks for the heads up :)