title: MySQL: GET_LOCK limits and issues
body: <p>I a need a database level synchronization. For this I'm using GET_LOCK('prefix.some_id', 0).
  At some moment GET_LOCK returns 1 for same key in different scripts on different hosts. What could be the problem? I need lots of those locks, 5-7k approximately.</p>
  
  <p>Any ideas?</p>