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php, mysql - Too many connections to database error

Good day to all. I have an odd error. I have created a chat that works like this:

  • questions/answers are inserted into a db
  • every 2 seconds an ajax request is sent to a php script that fetch the new questions/answers

It worked fine until today when I got this error:

Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [1040] Too many connections' in /var/www/html/dbdev/include/Zend/Db/Adapter/Pdo/Abstract.php:129 
Stack trace: #0 /var/www/html/dbdev/include/Zend/Db/Adapter/Pdo/Abstract.php(129): PDO->__construct('mysql:host=loca...', '', '', Array) 
s#1 /var/www/html/dbdev/include/Zend/Db/Adapter/Pdo/Mysql.php(96): Zend_Db_Adapter_Pdo_Abstract->_connect() 
s#2 /var/www/html/dbdev/include/Zend/Db/Adapter/Abstract.php(448): Zend_Db_Adapter_Pdo_Mysql->_connect() 
s#3 /var/www/html/dbdev/include/Zend/Db/Adapter/Pdo/Abstract.php(238): Zend_Db_Adapter_Abstract->query('select profile_...', Array) 
s#4 /var/www/html/dbdev/include/Zend/Db/Adapter/Abstract.php(782): Zend_Db_Adapter_Pdo_Abstract->query('select profile_...', Array) 
s#5 /var/www/html/dbdev/include/Profile.php(43): Zend_Db_Adapter_Abstract->fetchPairs('select profile_...') 
s#6 /var/www/html/dbdev/public_html/index.php(29): Profile->load() 
s#7 {main} Next exception 'Zend_Db_Adapter_Exception' with in /var/www/html/dbdev/include/Zend/Db/Adapter/Pdo/Abstract.php on line 144

The problem is that we were not that many... (8) and I don't think the db could not support more than 8 to 16 connections simultaneously (on specifications is written that the chat must support 50-100 users so 8 is... small).

So... can any1 tell me why did this happen (yesterday we were 15 and worked fine) and how to solve it? Thank you for your help. If you need any code samples just ask.

like image 360
zozo Avatar asked Feb 18 '11 10:02

zozo


People also ask

What causes MySQL too many connections?

The MySQL “Too many connections” error occurs when more queries are sent to a MySQL database than can be processed. The error can be fixed by setting a new number of maximum connections in the configuration file or globally.

How do I check for too many connections in MySQL?

If clients encounter Too many connections errors when attempting to connect to the mysqld server, all available connections are in use by other clients. The permitted number of connections is controlled by the max_connections system variable. To support more connections, set max_connections to a larger value.


2 Answers

There are a bunch of different reasons for the "Too Many Connections" error.

Check out this FAQ page on MySQL.com: http://dev.mysql.com/doc/refman/5.5/en/too-many-connections.html

Check your my.cnf file for "max_connections". If none exist try:

[mysqld]
set-variable=max_connections=250

However the default is 151, so you should be okay.

If you are on a shared host, it might be that other users are taking up too many connections.

Other problems to look out for is the use of persistent connections and running out of diskspace.

like image 184
Alexandru Petrescu Avatar answered Oct 02 '22 07:10

Alexandru Petrescu


The error SQLSTATE[HY000] [1040] Too many connections is an SQL error, and has to do with the sql server. There could be other applications connecting to the server. The server has a maximum available connections number.

If you have phpmyadmin, you can use the 'variables' tab to check what the setting is.

You can also query the status table like so:

show status like '%onn%';

Or some variance on that. check the manual for what variables there are

(be aware, 'connections' is not the current connections, check that link :) )

like image 37
Nanne Avatar answered Oct 02 '22 07:10

Nanne