MYSQL_WAIT_TIMEOUT_MAX = 2147483

def test_connection(extra_conf = {})
  conf = {
    :host => "HOST_NAME",
    :username => "USER_NAME",
    :password => "PASSWORD",
    :database => "DATABASE_NAME",
    :adapter  => "mysql2"
  }
  ActiveRecord::Base.establish_connection(conf.merge(extra_conf))
  puts ActiveRecord::Base.connection.execute("SHOW VARIABLES LIKE \"wait_timeout\"").to_a.join(" : ")
  seconds_to_sleep = [ 60, 120, 180, 240, 300, 360]
  seconds_to_sleep.each do |seconds|
    sleep seconds
    puts ActiveRecord::Base.connection.active? ? "Connection up !" : "Connection lost !"
  end
end

# After more than 5 minutes of inactivity, the ActiveRecord connection becomes disconnected, which results in the "MySQL Server Has Gone Away" error":
irb(main):058:0> test_connection(:wait_timeout => MYSQL_WAIT_TIMEOUT_MAX)
wait_timeout : 2147483
Connection up !
Connection up !
Connection up !
Connection up !
Connection up !
Connection lost !
=> [60, 120, 180, 240, 300, 360]