I get too connection error on my site from today…
PDOException: SQLSTATE[08004] [1040] Too many connections in lock_may_be_available() (line 167 of /home/sevensibir/domains/7sib.ir/public_html/includes/lock.inc).
I think its an attack, because when I run mysqltuner.pl I get:
[!!] Highest connection usage: 100% (152/151)
but I know I have about 500 visit per day. how can I found if this is an attack.
and how can I stop it?
Best Answer
No.
There's nothing here to support your hypothesis. If you can't confirm that this level of traffic was abnormal then you haven't got adequate monitoring in place.
For capacity management this is a useless statistic. You need to know how many concurrent connections you have, how long they last, and what proportion of them are for static content. Thn you need to start asking yourself why so many connections are appearing at the database - you're may be allowing too many connections on the webserver.
The FIRST thing you need to do is get machinery in place to be able to answer these questions quickly, then you can start thinking about measures to ensure continuity of service. For DOS prevention there's a lot of things you do with iptables, using an application firewall or a feedback tool like fail2ban is helpful, but putting an event based reverse proxt server will have the biggest impact. Tuning your application, in particular the MySQL queries should give far greater capacity. A quick fix for capacity is, to check if your PHP code explicitly closes mysql connections - if not, then add an auto-prepend file which calls mysql_close() via register_shutdown_function()