b448b129d0
The parameter is now defined in the monitor. Further refactoring is needed to make the interface of the journal system simpler.
145 lines
5.4 KiB
Markdown
145 lines
5.4 KiB
Markdown
# Common Monitor Parameters
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This document lists optional parameters that all current monitors support.
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## Parameters
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### `user`
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Username used by the monitor to connect to the backend servers. If a server defines
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the `monitoruser` parameter, that value will be used instead.
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### `password`
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Password for the user defined with the `user` parameter. If a server defines
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the `monitorpw` parameter, that value will be used instead.
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### `monitor_interval`
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This is the time the monitor waits between each cycle of monitoring. The default
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value of 2000 milliseconds (2 seconds) should be lowered if you want a faster
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response to changes in the server states. The value is defined in milliseconds
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and the smallest possible value is 100 milliseconds.
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The default value of _monitor_interval_ was updated from 10000 milliseconds to
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2000 milliseconds in MaxScale 2.2.0.
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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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### `backend_connect_attempts`
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This parameter defines the maximum times a backend connection is attempted every
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monitoring loop. The default is 1. Every attempt may take up to
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`backend_connect_timeout` seconds to perform. If none of the attempts are
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successful, the backend is considered to be unreachable and down.
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```
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backend_connect_attempts=3
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```
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### `script`
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This command will be executed when a server changes its state. The parameter should be an absolute path to a command or the command should be in the executable path. The user which is used to run MaxScale should have execution rights to the file itself and the directory it resides in.
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```
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script=/home/user/myscript.sh initiator=$INITIATOR event=$EVENT live_nodes=$NODELIST
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```
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The following substitutions will be made to the parameter value:
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* `$INITIATOR` will be replaced with the IP and port of the server who initiated the event
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* `$EVENT` will be replaced with the name of the event
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* `$LIST` will be replaced with a list of server IPs and ports
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* `$NODELIST` will be replaced with a list of server IPs and ports that are running
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* `$SLAVELIST` will be replaced with a list of server IPs and ports that are slaves
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* `$MASTERLIST` will be replaced with a list of server IPs and ports that are masters
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* `$SYNCEDLIST` will be replaced with a list of server IPs and ports that are synced Galera nodes
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For example, the previous example will be executed as:
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```
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/home/user/myscript.sh initiator=[192.168.0.10]:3306 event=master_down live_nodes=[192.168.0.201]:3306,[192.168.0.121]:3306
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```
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### `events`
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A list of event names which cause the script to be executed. If this option is not defined, all events cause the script to be executed. The list must contain a comma separated list of event names.
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```
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events=master_down,slave_down
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```
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## Script events
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Here is a table of all possible event types and their descriptions that the monitors can be called with.
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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 gone down
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server_up |A server with no assigned role has come up
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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_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_ndb |A new MySQL Cluster node was found
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### `journal_max_age`
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The maximum journal file age in seconds. The default value is 28800 seconds.
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When the monitor starts, it reads any stored journal files. If the journal file
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is older than the value of _journal_max_age_, it will be removed and the monitor
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starts with no prior knowledge of the servers.
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## Monitor Crash Safety
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Starting with MaxScale 2.2.0, the monitor modules keep an on-disk journal of the
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latest server states. This change makes the monitors crash-safe when options
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that introduce states are used. It also allows the monitors to retain stateful
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information when MaxScale is restarted.
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For MySQL monitor, options that introduce states into the monitoring process are
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the `detect_stale_master` and `detect_stale_slave` options, both of which are
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enabled by default. Galeramon has the `disable_master_failback` parameter which
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introduces a state.
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The default location for the server state journal is in
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`/var/lib/maxscale/<monitor name>/monitor.dat` where `<monitor name>` is the
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name of the monitor section in the configuration file. If MaxScale crashes or is
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shut down in an uncontrolled fashion, the journal will be read when MaxScale is
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started. To skip the recovery process, manually delete the journal file before
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starting MaxScale.
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