MySql Proccesslist filled with “Sleep” Entries leading to “Too many Connections”?

Question

I\'d like to ask your help on a longstanding issue with php/mysql connections.

Every time I execute a \"SHOW PROCESSLIST\" command it shows me about 400 idle (Status

Answer 1

Basically, you get connections in the Sleep state when :

• a PHP script connects to MySQL
• some queries are executed
• then, the PHP script does some stuff that takes time
  • without disconnecting from the DB
• and, finally, the PHP script ends
  • which means it disconnects from the MySQL server

So, you generally end up with many processes in a Sleep state when you have a lot of PHP processes that stay connected, without actually doing anything on the database-side.

A basic idea, so : make sure you don't have PHP processes that run for too long -- or force them to disconnect as soon as they don't need to access the database anymore.

Another thing, that I often see when there is some load on the server :

• There are more and more requests coming to Apache
  • which means many pages to generate
• Each PHP script, in order to generate a page, connects to the DB and does some queries
• These queries take more and more time, as the load on the DB server increases
• Which means more processes keep stacking up

A solution that can help is to reduce the time your queries take -- optimizing the longest ones.