title: MySql Slave, how to check if it is used
body: <p>I've configured a master-slave replication and everything seems working properly and the slave is running with 0 seconds behind master. Now I want to remove the word "seems".</p>
  
  <p>I'd expect to have a gain in reads, but if I execute a heavy query on Master nothing happens on the slave as if it's not used and I'm saying this because the load is 0, connections are not increased, selects per seconds are 0 and innodb reads per seconds are 0 (data from mysql workbench).</p>
  
  <p>Did I miss anything on the config side? How can i properly test this? </p>