3.8 KiB
MySQL Monitor
Overview
The MySQL monitor is a monitoring module for MaxScale that monitors a Master-Slave replication cluster. It assigns master and slave roles inside MaxScale according to the acutal replication tree in the cluster.
Configuration
A minimal configuration of the MySQL monitor requires a set of servers for monitoring and a username and a password to connect to these servers. The user requires the REPLICATION CLIENT privilege to successfully monitor the state of the servers.
[MySQL Monitor]
type=monitor
module=mysqlmon
servers=server1,server2,server3
user=myuser
passwd=mypwd
Optional parameters
Here are optional parameters for the MySQL monitor that change the way it behaves.
monitor_interval
This is the time the monitor waits between each cycle of monitoring. The default value of 10000 milliseconds (10 seconds) should be lowered if you want a faster response to changes in the server states. The value is defined in milliseconds and the smallest possible value is 100 illiseconds.
monitor_interval=2500
backend_connect_timeout
This parameter controls the timeout for connecting to a monitored server. It is in seconds and the minimum value is 1 second. The default value for this parameter is 3 seconds.
backend_connect_timeout=6
backend_write_timeout
This parameter controls the timeout for writing to a monitored server. It is in seconds and the minimum value is 1 second. The default value for this parameter is 2 seconds.
backend_write_timeout=4
backend_read_timeout
This parameter controls the timeout for reading from a monitored server. It is in seconds and the minimum value is 1 second. The default value for this parameter is 1 seconds.
backend_read_timeout=2
detect_replication_lag
Detect replication lag between the master and the slaves. This allows the routers to route read queries to only slaves that are up to date.
detect_replication_lag=true
detect_stale_master
Allow previous master to be available even in case of stopped or misconfigured replication. This allows services that depend on master and slave roles to continue functioning as long as the master server is available.
This is a situation which can happen if all slave servers are unreachable or the replication breaks for some reason.
detect_stale_master=true
script
This script will be executed when a server changes its state. The parameter should be an absolute path to the script or it should be in the executable path.
script=/home/user/script.sh
This script will be called with the following command line arguments.
<name of the script> --event=<event type> --node=<server whose state changed> --nodelist=<list of all servers>
Here is a table of all possible event names and their descriptions.
| Event Name | Description |
|---|---|
| master_down | A Master server has gone down |
| master_up | A Master server has come up |
| slave_down | A Slave server has gone down |
| slave_up | A Slave server has come up |
| server_down | A server with no assigned role has done down |
| server_up | A server with no assigned role has come up |
| synced_down | A synced Galera node has come up |
| synced_up | A synced Galera node has gone down |
| donor_down | A donor Galera node has come up |
| donor_up | A donor Galera node has gone down |
| ndb_down | A MySQL Cluster node has gone down |
| ndb_up | A MySQL Cluster node has come up |
| lost_master | A server lost Master status |
| lost_slave | A server lost Slave status |
| lost_synced | A Galera node lost synced status |
| lost_donor | A Galera node lost donor status |
| lost_ndb | A MySQL Cluster node lost node membership |
| new_master | A new Master was detected |
| new_slave | A new Slave was detected |
| new_synced | A new synced Galera node was detected |
| new_donor | A new donor Galera node was detected |
| new_ndb | A new MySQL Cluster node was found |