Mysql – View active MySQL connections per user

max-connectionsMySQLmysql-5.5users

I need a query that will give me the active or open number of connections to a certain database for a certain user. I have been searching for hours and have come up with nothing so far. I am close, so here is what I have tried.

SHOW STATUS WHERE `variable_name` = 'Threads_connected';
SHOW STATUS LIKE '%onn%';
SELECT * FROM information_schema.processlist WHERE USER='database_user';

I work for a web hosting company, and one of our clients keeps hitting his max_user_connections limit, so in troubleshooting why I need to know how many connections his user is using right now since he is no a shared server. I am currently using MySQL (InnoDB) version 5.5.36. Any help would be greatly appreciated!

Best Answer

What you need is a breakdown by user and hostname along with a total

SELECT IFNULL(usr,'All Users') user,IFNULL(hst,'All Hosts') host,COUNT(1) Connections
FROM
(
    SELECT user usr,LEFT(host,LOCATE(':',host) - 1) hst
    FROM information_schema.processlist
    WHERE user NOT IN ('system user','root')
) A GROUP BY usr,hst WITH ROLLUP;

This will handle host address that have a colon separating hostname and port number

I hope everybody is not logging in as root

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MySQL – What Are User Connections and When Are They Created and Destroyed

Please notice the makeup of mysql.user:

mysql> show create table mysql.user\G
*************************** 1. row ***************************
       Table: user
Create Table: CREATE TABLE `user` (
  `Host` char(60) COLLATE utf8_bin NOT NULL DEFAULT '',
  `User` char(16) COLLATE utf8_bin NOT NULL DEFAULT '',
  `Password` char(41) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL DEFAULT '',
  `Select_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Insert_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Update_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Delete_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Create_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Drop_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Reload_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Shutdown_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Process_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `File_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Grant_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `References_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Index_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Alter_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Show_db_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Super_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Create_tmp_table_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Lock_tables_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Execute_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Repl_slave_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Repl_client_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Create_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Show_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Create_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Alter_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Create_user_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Event_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Trigger_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `Create_tablespace_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
  `ssl_type` enum('','ANY','X509','SPECIFIED') CHARACTER SET utf8 NOT NULL DEFAULT '',
  `ssl_cipher` blob NOT NULL,
  `x509_issuer` blob NOT NULL,
  `x509_subject` blob NOT NULL,
  `max_questions` int(11) unsigned NOT NULL DEFAULT '0',
  `max_updates` int(11) unsigned NOT NULL DEFAULT '0',
  `max_connections` int(11) unsigned NOT NULL DEFAULT '0',
  `max_user_connections` int(11) unsigned NOT NULL DEFAULT '0',
  `plugin` char(64) COLLATE utf8_bin DEFAULT '',
  `authentication_string` text COLLATE utf8_bin,
  PRIMARY KEY (`Host`,`User`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='Users and global privileges'
1 row in set (0.00 sec)

Notice the column max_user_connections. It puts a moratorium on the number of connections a user may make per hour. Check and make sure the user '557574_prod' isn't connecting to mysql a ton of times within less than an hour.

This is used in conjunction with the option max_user_connections that you can set in /etc/my.cnf

Please change either max_user_connections in /etc/my.cnf or, if the individual user has this column set, that column mysql.user.max_user_connections. If you have no config control over my.cnf and you cannot do SQL against the mysql schema, then you beg and implore your hosting company to raise those limits for you.

I believe you can set the max_user_connections as a session variable, but you may need certain privileges, probably SUPER.

As for establish connections, you need to keep those connections open. Perhaps sending a heartbeat of some kind by doing a SELECT. But guess what ??? The db columns max_questions monitor SELECT queries per hour and max_updates monitors INSERTs, UPDATEs, DELETEs per hour. YOu may need to check these columns in mysql.user. You can quickly check those number with:

SHOW GRANTS;

I am not sure if the the user's per-hour connection limits are per thread or per user. You could answer that quickly by connecting to the DB aggressively using 2 or 3 DB connecitons at the same time and the error message should manifest itself. It is up you how to count the number of connections, perhaps "SHOW STATUS LIKE 'Connections';" It should reach either the max limits of the connection within the one connections or it could be the sum of all connections' connection status value.

Please also check the wait_timeout and interactive_timeout values. The default is 28800 in a standalone server. They may be set already. You cannot set them within a current connection. You must be able to set them as follows: (for new conenctions coming)

SET GLOBAL interactive_timeout = 86400;
SET GLOBAL wait_timeout = 86400;

If you cannot run even these commands, my condolences !!! :(

Mysql not closing connections

According to MySQL documentation the Connections status variable shows "The number of connection attempts (successful or not) to the MySQL server." This means that it does not represent current open connections, but all connection attempts since the server has been started.

The variable showing number of current open connections, again according to MySQ docs, is Threads_connected.

Best Answer

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MySQL – What Are User Connections and When Are They Created and Destroyed

Mysql not closing connections

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