Added Galera monitor documentation.
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Markus Makela
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Documentation/monitors/Galera-Monitor.md
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Documentation/monitors/Galera-Monitor.md
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# Galera Monitor
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## Overview
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The Galera Monitor is a monitoring module for MaxScale that monitors a Galera cluster. It detects whether nodes are a part of the cluster and if they are in sync with the rest of the cluster. It can also assign master and slave roles inside MaxScale, allowing Galera clusters to be used with modules designed for traditional master-slave clusters.
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## Configuration
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A minimal configuration for a 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.
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```
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[MySQL Monitor]
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type=monitor
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module=galeramon
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servers=server1,server2,server3
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user=myuser
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passwd=mypwd
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```
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## Optional parameters for all monitors
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Here are optional parameters that are common for all the monitors.
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### `monitor_interval`
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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.
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```
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monitor_interval=2500
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```
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### `backend_connect_timeout`
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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.
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```
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backend_connect_timeout=6
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```
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### `backend_write_timeout`
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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.
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```
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backend_write_timeout=4
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```
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### `backend_read_timeout`
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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.
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```
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backend_read_timeout=2
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```
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## Galera Monitor optional parameters
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These are optional parameters specific to the Galera Monitor.
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### `disable_master_failback`
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If a node marked as master inside MaxScale happens to fail and the master status is assigned to another node MaxScale will normally return the master status to the original node after it comes back up. With this option enabled, if the master status is assigned to a new node it will not be reassigned to the original node for as long as the new master node is running.
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```
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disable_master_failback=true
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```
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### `available_when_donor`
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This option only has an effect if there is a single Galera node being backed up an XtraBackup instance. This causes the initial node to go into Donor state which would normally prevent if from being marked as a valid server inside MaxScale. If this option is enabled, a single node in Donor state where the method is XtraBackup will be kept in Synced state.
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```
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available_when_donor=true
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```
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### `disable_master_role_setting`
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This disables the assingment of master and slave roles to the Galera cluster nodes. If this option is enabled, Synced is the only status assigned by this monitor.
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```
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disable_master_role_setting=true
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```
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### `script`
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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.
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```
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script=/home/user/script.sh
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```
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This script will be called with the following command line arguments.
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```
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<name of the script> --event=<event type> --initiator=<server whose state changed> --nodelist=<list of all servers>
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```
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Here is a table of all possible event types and their descriptions.
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Event Name|Description
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----------|----------
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master_down|A Master server has gone down
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master_up|A Master server has come up
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slave_down|A Slave server has gone down
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slave_up|A Slave server has come up
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server_down|A server with no assigned role has done down
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server_up|A server with no assigned role has come up
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synced_down|A synced Galera node has come up
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synced_up|A synced Galera node has gone down
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donor_down|A donor Galera node has come up
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donor_up|A donor Galera node has gone down
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ndb_down|A MySQL Cluster node has gone down
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ndb_up|A MySQL Cluster node has come up
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lost_master|A server lost Master status
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lost_slave|A server lost Slave status
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lost_synced|A Galera node lost synced status
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lost_donor|A Galera node lost donor status
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lost_ndb|A MySQL Cluster node lost node membership
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new_master|A new Master was detected
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new_slave|A new Slave was detected
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new_synced|A new synced Galera node was detected
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new_donor|A new donor Galera node was detected
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new_ndb|A new MySQL Cluster node was found
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@ -2,11 +2,11 @@
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## Overview
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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.
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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.
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## Configuration
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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.
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A minimal configuration for a 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.
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```
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[MySQL Monitor]
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@ -18,9 +18,9 @@ passwd=mypwd
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```
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## Optional parameters
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## Optional parameters for all monitors
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Here are optional parameters for the MySQL monitor that change the way it behaves.
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Here are optional parameters that are common for all the monitors.
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### `monitor_interval`
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@ -54,6 +54,10 @@ This parameter controls the timeout for reading from a monitored server. It is i
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backend_read_timeout=2
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```
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## MySQL Monitor optional parameters
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These are optional parameters specific to the MySQL Monitor.
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### `detect_replication_lag`
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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.
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@ -86,7 +90,7 @@ This script will be called with the following command line arguments.
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```
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<name of the script> --event=<event type> --initiator=<server whose state changed> --nodelist=<list of all servers>
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```
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Here is a table of all possible event names and their descriptions.
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Here is a table of all possible event types and their descriptions.
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Event Name|Description
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----------|----------
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