Rake task to download a sql dump from a heroku app

heroku.rake

namespace :heroku do
  def app_name
    @app_name ||= Heroku::Command::BaseWithApp.new([]).app
  end

  def latest_bundle(timeout = 30)
    puts "Attempting to get latest bundle..."
    get_bundle = lambda do
      bundles = Heroku::Command.run('bundles', {})
      bundles.sort { |b1, b2| b1[:created_at] <=> b2[:created_at] }
      bundles.last
    end

    bundle = nil
    require 'timeout'
    Timeout.timeout(timeout) do
      while bundle.nil? || bundle[:state] == 'capturing' do
        sleep 0.5
        bundle = get_bundle.call
      end
    end
    puts "Latest bundle capture has completed"

    bundle
  end

  def invoke(task)
    Rake::Task["heroku:#{task}"].invoke
  end

  task :heroku_setup do
    require 'heroku'
    require 'heroku/command'
  end

  task :unpack_tar_setup do
    require 'zlib'
    require 'archive/tar/minitar'
  end

  task :destroy_all_bundles => :heroku_setup do |t|
    Heroku::Command.run('bundles', {}).try(:each) do |bundle|
      Heroku::Command.run('bundles:destroy', [bundle[:name]])
    end
  end

  task :capture_new_bundle => :heroku_setup do |t|
    begin
      Heroku::Command.run('bundles:capture', [])
    rescue SystemExit
      puts "Apparently only one bundle is allowed.  Deleting all bundles so we can try again..."
      invoke('destroy_all_bundles')
      Heroku::Command.run('bundles:capture', [])
    end
  end

  task :download_newest_bundle => :heroku_setup do |t|
    bundle = latest_bundle
    puts "Downloading latest bundle..."
    Heroku::Command.run('bundles:download', [bundle[:name]])
  end

  task :unpack_sqldump, :tar_file, :extract_to, :needs => :unpack_tar_setup do |t, args|
    tgz = Zlib::GzipReader.new(File.open(args.tar_file, 'rb'))

    Archive::Tar::Minitar::Input.open(tgz) do |inp|
      inp.each do |entry|
        if entry.full_name =~ /pgdump\.sql/
          inp.extract_entry(args.extract_to, entry)
          ENV['SQL_DUMP_FILE'] = File.join(args.extract_to, entry.full_name) # so other rake tasks can use it...
          puts "sql dump file written to: #{ENV['SQL_DUMP_FILE']}"
        end
      end
    end
  end

  task :download_sql_dump => :environment do |t|
    invoke('capture_new_bundle')
    invoke('download_newest_bundle')
    tar_file = File.join(Rails.root, "#{app_name}.tar.gz")
    extract_to = File.join(Rails.root, "tmp", "bundles")
    Rake::Task["heroku:unpack_sqldump"].invoke(tar_file, extract_to)
  end
end