What tools do you use to monitor the health of your MySQL server instance? Are they for free or commercial?
I like SQLyog for remote administration of mySQL. Nice GUI environment, and there is a free community edition.
This company also makes MONyog, a mySQL monitoring solution, but it's not free and I haven't played with it.
Apart from running cacti to graph the mysql performance over time, we have mysqltuner.com setup to send us a daily report of any variables on the server we should be keeping an eye on.
We use hyperic, it is an open source application, but there is a commercial product as well if you want. It also monitors the operating system, web servers etc.
Don't forget to monitor the underlying platform. I would monitor
- IOPS on the log, data and tmp devices (you do have those on three seperate LUNs don't you ?)
- Swapping (more than a few pages / second is bad for mysql, google "mysql swappiness" to find out why)
- Memory statistics for the host OS. A general rule of thumb I follow is to allocate no more than 80% to the mysql process to leave some room for the OS and the buffer cache
You can use SNMP and Cacti to monitor all of these things
Basic monitoring via the nagios nagios_mysql plugin, added a small custom script to monitor slaves status and slavelag.
It's not strictly monitoring but you can use mysqlreport to have a good overview of how well your mysql server is performing and if it is properly configured.
Actually it depends on the database(s) that is running on the sever.
I usually check for the
- number of queries
- depending on database
- slow query log
- mysql connection from a remote host to a certain database
- check that it works from the right hosts
- check that it fails from the right hosts
- select the current time to be sure it's correct
- select for collations/encodings
- connected users
on the framework side I'm using munin for everything that could give me metrics and nagios (soon to be icinga) for everything that gives me status information.
For more comprehensive monitoring of MySQL (but commercial, so only if your database is worth it) check out www.LogicMonitor.com. No configuration required (detects storage engine types, replication status, etc); provides tuning recommendations; full historical graphing and alerting in one system; very extensible, and will monitor the rest of your datacenter infrastructure.