Wait for db. Useful in a dockerized setup

db.rake

namespace :db do
  desc "Wait for db. Used for initial boot up"
  task wait: :environment do
    puts "*** Giving DB time to boot"
    catch :done do
      10.times do
        Timeout.timeout(1) do
          begin
            ActiveRecord::Base.establish_connection
            ActiveRecord::Base.connection.execute("SELECT NOW()")
            puts "*** DB responded"
            throw :done
          rescue Timeout::Error, PG::ConnectionBad, Mysql2::Error, ActiveRecord::NoDatabaseError => err
            puts err
          end
        end
        sleep 1
      end
      fail "Did not get a connection"
    end
  end
end