Quick and dirty script to upgrade a Heroku Postgres DB according to https://devcenter.heroku.com/articles/heroku-postgres-follower-databases#database-upgrades-and-migrations-with-changeovers Usage: ruby upgrade.rb <app_name> with_worker

upgrade.rb

@app = ARGV[0]
puts @app

@scale_worker = (ARGV.last == "with_worker")

def prepare
  db_info = `heroku pg:info -a #{@app}`
  @db_name = db_info.split("\n").first.split(" ")[1]

  follower_available = db_info.include? "Fork/Follow: Available"
  if not follower_available
    puts "Follower not available."
    exit
  end

  follower_command = "heroku addons:add heroku-postgresql:crane --follow #{@db_name} -a #{@app}"
  puts "Doing: '#{follower_command}'"
  follower_info = `#{follower_command}`
  @follower_db = follower_info[/(?<=(Attached as )).*/]
  if not @follower_db or @follower_db.empty?
    puts "Could not add follower"
    exit
  else
    puts "Added follower at #{@follower_db}"
  end

  puts "Waiting.."
  system "heroku pg:wait -a #{@app}"

  puts "Maintenance mode ON"
  system "heroku maintenance:on -a #{@app}"
  system "heroku scale worker=0 -a #{@app}" if @scale_worker

  puts "Check follower is up to date.."
  pg_status = `heroku pg:info -a #{@app}`
  if not pg_status.include? "Behind By:   0 commits"
    puts "Follower hasn't caught up"
    exit
  end
  puts pg_status
end

def promote
  @follower_db ||= ARGV[2]
  puts "Using follower #{@follower_db}"


  system "heroku pg:unfollow #{@follower_db} -a #{@app} --confirm #{@app}"
  system "heroku pg:promote #{@follower_db} -a #{@app} --confirm #{@app}"

  puts "Maintenance OFF"
  system "heroku ps:scale worker=1 -a #{@app}" if @scale_worker
  system "heroku maintenance:off -a #{@app}"

  if @db_name
    puts "Back up and running. Remember to remove the old database with:"
    puts "heroku addons:remove #{@db_name.gsub('_URL', '')} -a #{@app}"
  else
    puts "Back up and running. Remember to remove the old database."
  end
end

if ARGV[1] == "prepare"
  prepare
elsif ARGV[1] == "promote"
  promote
else
  prepare
  promote
end