116 lines
3.8 KiB
Markdown
116 lines
3.8 KiB
Markdown
# 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> --initiator=<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
|
|
|