Re: mysql max_connections

[Rick James]

I doubt if you are really using more than a few dozen Apache children. Also, I suspect that Apache would grind to a halt if it had anywhere near 400 actions in progress at once. What happens is that the Apache children fight for resources (CPU or core or disk or mysql or whatever) and all the children slow down. This leads to poor response time for each user.

I rarely see an Apache server that is doing nontrivial stuff need more than 30 for MaxClients.

What activity do you have other than from Apache? (I would expect very few.)

Does web page need more than one connection to MySQL? (I would expect not.)

So, max_connections does not need to be more than a few more than Apache's MaxClients.

Similarly, if you have lots (say, 400) MySQL clients all hitting the same table, response will be not just poor, but terrible.

Do SHOW PROCESSLIST. How many processes are
* "Sleep" -- that is, waiting for the UI to issue another query.
* "Locked" -- that is, blocked on resources (probably a table lock in MyISAM).
* or doing something useful.