Calculate number of transactions/second being ran against your MySQL DB.

monitor.rb

require 'mysql2'

$mysql = Mysql2::Client.new(
  host: 'localhost',
  username: 'root'
)

SLEEP_TIMEOUT=1.0

last_trx = 0
last_trx_at = Time.now

loop do
  result = $mysql.query("show status where Variable_name = 'Queries';")
  start_at = Time.now
  new_trx = result.first["Value"].to_i

  if last_trx > 0
    puts '%0.03f' % ((new_trx - last_trx) / (start_at - last_trx_at))
  end

  last_trx = new_trx
  last_trx_at = start_at

  sleep(SLEEP_TIMEOUT)
end