This article explains how MySQL settings can be optimized following a set of predetermined steps. The results are pretty reliable and we keep using this with a very high degree of success. This is something regularly done at Leanservers.
Tag Archives: mysql
Revoking MySQL Permissions
Usage:
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mysql> revoke PRIVILEGES [, GRANT OPTION] from 'USERNAME'@'SERVER'; mysql> flush privileges; |
Example:
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mysql> revoke all privileges, grant option from 'comsiteuatusr'@'10.135.7.114'; Query OK, 0 rows affected (0.00 sec) |
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mysql> flush privileges; Query OK, 0 rows affected (0.00 sec) |
See Also
Dumping a mysql database excluding one or several tables
If we need to dump a MySQL database and want to exclude table(s) we should use the option:
--ignore-table=db_name.tbl_nameDo not dump the given table, which must be specified using both the database and table names. To ignore multiple tables, use this option multiple times. This option also can be used to ignore views. Citation.
Example:
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mysqldump --ignore-table=cars.brands cars > cars.dump |
References
How to install MySQL Server on Debian Linux
While installing MySQL Server it is always good to keep in mind that the logs and data folders will potentially have a big size. By default MySQL keeps them in the root mount point (i.e. ‘/’). That may cause your database server system disk to get full, which is never a good idea.
This article describes how to move these two folders to ‘/home’ which is ideally mounted into another disk and has enough space to keep your database data and logs.
First, I install the required apt-get packages as follows:
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apt-get update apt-get install mysql-server |
To check the status:
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/etc/init.d/mysql status /usr/bin/mysqladmin Ver 8.41 Distrib 5.0.51a, for debian-linux-gnu on i486 Copyright (C) 2000-2006 MySQL AB This software comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to modify and redistribute it under the GPL license Server version 5.0.51a-24 Protocol version 10 Connection Localhost via UNIX socket UNIX socket /var/run/mysqld/mysqld.sock Uptime: 3 sec Threads: 1 Questions: 78 Slow queries: 0 Opens: 23 Flush tables: 1 Open tables: 17 Queries per second avg: 26.000. |
Now, stop MySQL, move the folders to the right location, reconfigure MySQL and start again:
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# Stop MySQL /etc/init.d/mysql stop # Move and reconfigure data mkdir /home/mysql mv /var/lib/mysql /home/mysql/mysql-data ln -s /home/mysql/mysql-data/ /var/lib/mysql # Move and reconfigure logs mv /var/log/mysql/ /home/mysql/mysql-logs ln -s /home/mysql/mysql-logs/ /var/log/mysql # Start MySQL and check that everything is OK /etc/init.d/mysql start /etc/init.d/mysql status /usr/bin/mysqladmin Ver 8.41 Distrib 5.0.51a, for debian-linux-gnu on i486 Copyright (C) 2000-2006 MySQL AB This software comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to modify and redistribute it under the GPL license Server version 5.0.51a-24 Protocol version 10 Connection Localhost via UNIX socket UNIX socket /var/run/mysqld/mysqld.sock Uptime: 14 sec Threads: 1 Questions: 78 Slow queries: 0 Opens: 23 Flush tables: 1 Open tables: 17 Queries per second avg: 5.571. |
These are some settings that I usually put on the /etc/mysql/my.cnf configuration file:
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# Here you can see queries with especially long duration log_slow_queries = /var/log/mysql/mysql-slow.log long_query_time = 1 log-queries-not-using-indexes # A server-id unique server-id = 177 log-bin = /var/log/mysql/mysql-bin.log log-bin-index = /var/log/mysql/mysql-bin.log innodb_file_per_table # Unique log names (this prevents replication breaking upon hostname change :-) relay-log = iamalsounique98127-relay-bin relay-log-index = iamalsounique98127-relay-bin # Taking care of the auto-increment values (for multi-master replication) auto_increment_increment = 10 auto_increment_offset = 1 |
For these changes to take effect, you would need to restart MySQL:
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/etc/init.d/mysql restart |
If you want to ignore databases or tables you may use the following options:
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binlog_ignore_db = information_schema replicate_ignore_db = information_schema binlog_ignore_db = mysql replicate_ignore_db = mysql # Ignore all the cache* tables which have caused DUPLICATE # ENTRY issues. Unai. replicate_wild_ignore_table = exampledb.cache% |
Having ‘binlog_ignore_db’ is enough to exclude databases from replication BUT having ‘replicate_ignore_db’ as well will make things clearer since the databases that are being ignored will appear in both the ‘SHOW SLAVE STATUS\G’ and ‘SHOW MASTER STATUS\G’.
Having HAProxy check mysql status through a xinetd script
HAProxy is able to load balance MySQL wonderfully. The main issue is how to make sure that the backend MySQL server to forward the request to is up and running (I mean not just to establish a connection to port 3306, I mean something more “complete”, that performs a little operation against the MySQL server).
It is possible to make haproxy check the status of a mysql server using a small shell script managed through the xinetd daemon.
What this script basically does is performs a basic operation against the mysql database then returns http status 200 if the operation was successful or http status 500 if it there was any error (i.e. mysql was not available).
Script
The script looks like this:
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#!/bin/bash # # This script checks if a mysql server is healthy running on localhost. It will # return: # # "HTTP/1.x 200 OK\r" (if mysql is running smoothly) # # - OR - # # "HTTP/1.x 500 Internal Server Error\r" (else) # # The purpose of this script is make haproxy capable of monitoring mysql properly # # Author: Unai Rodriguez # # It is recommended that a low-privileged-mysql user is created to be used by # this script. Something like this: # # mysql> GRANT SELECT on mysql.* TO 'mysqlchkusr'@'localhost' \ # -> IDENTIFIED BY '257retfg2uysg218' WITH GRANT OPTION; # mysql> flush privileges; MYSQL_HOST="localhost" MYSQL_PORT="3306" MYSQL_USERNAME="mysqlchkusr" MYSQL_PASSWORD="secret" TMP_FILE="/tmp/mysqlchk.out" ERR_FILE="/tmp/mysqlchk.err" # # We perform a simple query that should return a few results :-p # /usr/bin/mysql --host=$MYSQL_HOST --port=$MYSQL_PORT --user=$MYSQL_USERNAME \ --password=$MYSQL_PASSWORD -e"show databases;" > $TMP_FILE 2> $ERR_FILE # # Check the output. If it is not empty then everything is fine and we return # something. Else, we just do not return anything. # if [ "$(/bin/cat $TMP_FILE)" != "" ] then # mysql is fine, return http 200 /bin/echo -e "HTTP/1.1 200 OK\r\n" /bin/echo -e "Content-Type: Content-Type: text/plain\r\n" /bin/echo -e "\r\n" /bin/echo -e "MySQL is running.\r\n" /bin/echo -e "\r\n" else # mysql is fine, return http 503 /bin/echo -e "HTTP/1.1 503 Service Unavailable\r\n" /bin/echo -e "Content-Type: Content-Type: text/plain\r\n" /bin/echo -e "\r\n" /bin/echo -e "MySQL is *down*.\r\n" /bin/echo -e "\r\n" fi |
Steps on the MySQL server
First, you should create the script somewhere, and assign proper permissions:
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chown nobody /opt//mysqlchk chmod 744 /opt//mysqlchk |
Then, set permissions into the mysql server:
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mysql> GRANT SELECT on mysql.* TO 'mysqlchkusr'@'localhost' \ -> IDENTIFIED BY 'secret' WITH GRANT OPTION; mysql> flush privileges; mysql> exit |
Test:
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/opt/mysqlchk HTTP/1.x 200 OK |
Now, configure xinetd by adding this line at the bottom of /etc/services:
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mysqlchk 9200/tcp # mysqlchk |
Then add this file /etc/xinetd.d/mysqlchk:
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# default: on # description: mysqlchk service mysqlchk { flags = REUSE socket_type = stream port = 9200 wait = no user = nobody server = /opt/mysqlchk log_on_failure += USERID disable = no only_from = 0.0.0.0/0 # recommended to put the IPs that need # to connect exclusively (security purposes) per_source = UNLIMITED # Recently added (May 20, 2010) # Prevents the system from complaining # about having too many connections open from # the same IP. More info: # http://www.linuxfocus.org/English/November2000/article175.shtml } |
Restart xinetd (you can watch for issues on /var/log/syslog):
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/etc/init.d/xinetd stop /etc/init.d/xinetd start |
Test:
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telnet localhost 9200 Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. HTTP/1.1 200 OK Content-Type: Content-Type: text/plain MySQL is running. Connection closed by foreign host. |
Steps on the HAProxy server
Now, in order to make haproxy check the status of the mysql service through the xinetd-managed-script, we should add something similar to this on the haproxy.cfg file:
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listen MySQL 10.135.2.67:3306 mode tcp option httpchk server 10.135.2.69:3306 10.135.2.69:3306 check port 9200 inter 12000 rise 3 fall 3 source 10.135.2.67 |
What is important?
- option httpchk.- tells haproxy to check for full http response (i.e. http headers: 2xx OK or 5xx ERROR)
- check port XXXX.- tells haproxy to check the status of the service by sending an http request on that port