# Overview [MySQL](http://www.mysql.com) is a fast, stable and true multi-user, multi-threaded SQL database server. SQL (Structured Query Language) is the most popular database query language in the world. The main goals of MySQL are speed, robustness and ease of use. This charm also can deploy [Percona Server](http://www.percona.com/software/percona-server) is fork of MySQL by Percona Inc. which focuses on maximizing performance, particularly for heavy workloads. It is a drop-in replacement for MySQL and features XtraDB, a drop-in replacement for the InnoDB storage engine. # Usage ## General Usage To deploy a MySQL service: juju deploy mysql Once deployed, you can retrieve the MySQL root user password by logging in to the machine via `juju ssh` and readin the `/var/lib/mysql/mysql.passwd` file. To log in as root MySQL User at the MySQL console you can issue the following: juju ssh mysql/0 mysql -u root -p`sudo cat /var/lib/mysql/mysql.passwd` ## Backups The charm supports simple backups. To enable them set `backup_schedule` option. Optionally you can override default `backup_dir` and/or `backup_retention_count`: juju config mysql backup_schedule="45 5 * * *" # cron formatted schedule juju config mysql backup_dir="/mnt/backup" juju config mysql backup_retention_count=28 # Scale Out Usage ## Replication MySQL supports the ability to replicate databases to slave instances. This allows you, for example, to load balance read queries across multiple slaves or use a slave to perform backups, all whilst not impeding the master's performance. To deploy a slave: # deploy second service juju deploy mysql mysql-slave # add master to slave relation juju add-relation mysql:master mysql-slave:slave Any changes to the master are reflected on the slave. Any queries that modify the database(s) should be applied to the master only. The slave should be treated strictly as read only. You can add further slaves with: juju add-unit mysql-slave ## Monitoring This charm provides relations that support monitoring via either [Nagios](https://jujucharms.com/precise/nagios) or [Munin](https://jujucharms.com/precise/munin/). Refer to the appropriate charm for usage. # Configuration You can tweak various options to optimize your MySQL deployment: * max-connections - Maximum connections allowed to server or '-1' for default. * preferred-storage-engine - A comma separated list of storage engines to optimize for. First in the list is marked as default storage engine. 'InnoDB' or 'MyISAM' are acceptable values. * tuning-level - Specify 'safest', 'fast' or 'unsafe' to choose required transaction safety. This option determines the flush value for innodb commit and binary logs. Specify 'safest' for full ACID compliance. 'fast' relaxes the compliance for performance and 'unsafe' will remove most restrictions. * dataset-size - Memory allocation for all caches (InnoDB buffer pool, MyISAM key, query). Suffix value with 'K', 'M', 'G' or 'T' to indicate unit of kilobyte, megabyte, gigabyte or terabyte respectively. Suffix value with '%' to use percentage of machine's total memory. * query-cache-type - Specify 'ON', 'DEMAND' or 'OFF' to turn query cache on, selectively (dependent on queries) or off. * query-cache-size - Size of query cache (no. of bytes) or '-1' to use 20% of memory allocation. Each of these can be applied by running: juju config