# MaxScale 21.06 Common Monitor Parameters

This document settings supported by all monitors. These should be defined\
in the monitor section of the configuration file.

* [Common Monitor Parameters](#common-monitor-parameters)
  * [Parameters](#parameters)
    * [module](#module)
    * [user](#user)
    * [password](#password)
    * [servers](#servers)
    * [monitor\_interval](#monitor_interval)
    * [backend\_connect\_timeout](#backend_connect_timeout)
    * [backend\_write\_timeout](#backend_write_timeout)
    * [backend\_read\_timeout](#backend_read_timeout)
    * [backend\_connect\_attempts](#backend_connect_attempts)
    * [disk\_space\_threshold](#disk_space_threshold)
    * [disk\_space\_check\_interval](#disk_space_check_interval)
    * [script](#script)
    * [script\_timeout](#script_timeout)
    * [events](#events)
    * [journal\_max\_age](#journal_max_age)
  * [Monitor Crash Safety](#monitor-crash-safety)
  * [Script example](#script-example)

### Parameters

#### `module`

* Type: string
* Mandatory: Yes
* Dynamic: No

The monitor module this monitor should use. Typically `mariadbmon` or`galeramon`.

#### `user`

* Type: string
* Mandatory: Yes
* Dynamic: Yes

Username used by the monitor to connect to the backend servers. If a server defines\
the `monitoruser` parameter, that value will be used instead.

#### `password`

* Type: string
* Mandatory: Yes
* Dynamic: Yes

Password for the user defined with the `user` parameter. If a server defines\
the `monitorpw` parameter, that value will be used instead.

**Note:** In older versions of MaxScale this parameter was called `passwd`. The\
use of `passwd` was deprecated in MaxScale 2.3.0.

#### `servers`

* Type: string
* Mandatory: Yes
* Dynamic: Yes

A comma-separated list of servers the monitor should monitor.

```
servers=MyServer1,MyServer2
```

#### `monitor_interval`

* Type: [duration](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide)
* Mandatory: No
* Dynamic: Yes
* Default: `2s`

Defines how often the monitor updates the status of the servers. Choose a lower\
value if servers should be queried more often. The smallest possible value is\
100 milliseconds. If querying the servers takes longer than `monitor_interval`,\
the effective update rate is reduced.

```
monitor_interval=2s
```

The interval is specified as documented [here](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide). If no explicit unit\
is provided, the value is interpreted as milliseconds in MaxScale 2.4. In subsequent\
versions a value without a unit may be rejected.

#### `backend_connect_timeout`

* Type: [duration](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide)
* Mandatory: No
* Dynamic: Yes
* Default: `3s`

This parameter controls the timeout for connecting to a monitored server.\
The interval is specified as documented [here](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide). If no explicit unit\
is provided, the value is interpreted as seconds in MaxScale 2.4. In subsequent\
versions a value without a unit may be rejected. Note that since the granularity\
of the timeout is seconds, a timeout specified in milliseconds will be rejected,\
even if the duration is longer than a second. The minimum value is 1 second.

```
backend_connect_timeout=3s
```

#### `backend_write_timeout`

* Type: [duration](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide)
* Mandatory: No
* Dynamic: Yes
* Default: `3s`

This parameter controls the timeout for writing to a monitored server.\
The timeout is specified as documented [here](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide). If no explicit unit\
is provided, the value is interpreted as seconds in MaxScale 2.4. In subsequent\
versions a value without a unit may be rejected. Note that since the granularity\
of the timeout is seconds, a timeout specified in milliseconds will be rejected,\
even if the duration is longer than a second. The minimum value is 1 seconds.

```
backend_write_timeout=3s
```

#### `backend_read_timeout`

* Type: [duration](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide)
* Mandatory: No
* Dynamic: Yes
* Default: `3s`

This parameter controls the timeout for reading from a monitored server.\
The timeout is specified as documented [here](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide). If no explicit unit\
is provided, the value is interpreted as seconds in MaxScale 2.4. In subsequent\
versions a value without a unit may be rejected. Note that since the granularity\
of the timeout is seconds, a timeout specified in milliseconds will be rejected,\
even if the duration is longer than a second. The minimum value is 1 second.

```
backend_read_timeout=3s
```

#### `backend_connect_attempts`

* Type: number
* Mandatory: No
* Dynamic: Yes
* Default: `1`

This parameter defines the maximum times a backend connection is attempted every\
monitoring loop. Every attempt may take up to `backend_connect_timeout` seconds\
to perform. If none of the attempts are successful, the backend is considered to\
be unreachable and down.

```
backend_connect_attempts=1
```

#### `disk_space_threshold`

* Type: string
* Mandatory: No
* Dynamic: Yes
* Default: None

This parameter duplicates the `disk_space_threshold`[server parameter](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide).\
If the parameter has *not* been specified for a server, then the one specified\
for the monitor is applied.

**NOTE**: Since MariaDB 10.4.7, MariaDB 10.3.17 and MariaDB 10.2.26, the\
information will be available *only* if the monitor user has the `FILE`\
privilege.

That is, if the disk configuration is the same on all servers monitored by\
the monitor, it is sufficient (and more convenient) to specify the disk\
space threshold in the monitor section, but if the disk configuration is\
different on all or some servers, then the disk space threshold can be\
specified individually for each server.

For example, suppose `server1`, `server2` and `server3` are identical\
in all respects. In that case we can specify `disk_space_threshold`\
in the monitor.

```
[server1]
type=server
...

[server2]
type=server
...

[server3]
type=server
...

[monitor]
type=monitor
servers=server1,server2,server3
disk_space_threshold=/data:80
...
```

However, if the servers are heterogeneous with the disk used for the\
data directory mounted on different paths, then the disk space threshold\
must be specified separately for each server.

```
[server1]
type=server
disk_space_threshold=/data:80
...

[server2]
type=server
disk_space_threshold=/Data:80
...

[server3]
type=server
disk_space_threshold=/DBData:80
...

[monitor]
type=monitor
servers=server1,server2,server3
...
```

If *most* of the servers have the data directory disk mounted on\
the same path, then the disk space threshold can be specified on\
the monitor and separately on the server with a different setup.

```
[server1]
type=server
disk_space_threshold=/DbData:80
...

[server2]
type=server
...

[server3]
type=server
...

[monitor]
type=monitor
servers=server1,server2,server3
disk_space_threshold=/data:80
...
```

Above, `server1` has the disk used for the data directory mounted\
at `/DbData` while both `server2` and `server3` have it mounted on`/data` and thus the setting in the monitor covers them both.

#### `disk_space_check_interval`

* Type: [duration](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide)
* Mandatory: No
* Dynamic: Yes
* Default: `0s`

With this parameter it can be specified the minimum amount of time\
between disk space checks. The interval is specified as documented [here](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide). If no explicit unit\
is provided, the value is interpreted as milliseconds in MaxScale 2.4. In subsequent\
versions a value without a unit may be rejected.\
The default value is 0, which means that by default the disk space\
will not be checked.

Note that as the checking is made as part of the regular monitor interval\
cycle, the disk space check interval is affected by the value of`monitor_interval`. In particular, even if the value of`disk_space_check_interval` is smaller than that of `monitor_interval`,\
the checking will still take place at `monitor_interval` intervals.

#### `script`

* Type: string
* Mandatory: No
* Dynamic: Yes
* Default: None

This command will be executed on a server state change. The parameter should\
be an absolute path to a command or the command should be in the executable\
path. The user running MaxScale should have execution rights to the file itself\
and the directory it resides in. The script may have placeholders which\
MaxScale will substitute with useful information when launching the script.

The placeholders and their substitution results are:

* `$INITIATOR` -> IP and port of the server which initiated the event
* `$EVENT` -> event description, e.g. "server\_up"
* `$LIST` -> list of IPs and ports of all servers
* `$NODELIST` -> list of IPs and ports of all running servers
* `$SLAVELIST` -> list of IPs and ports of all slave servers
* `$MASTERLIST` -> list of IPs and ports of all master servers
* `$SYNCEDLIST` -> list of IPs and ports of all synced Galera nodes
* `$PARENT` -> IP and port of the parent of the server which initiated the event.\
  For master-slave setups, this will be the master if the initiating server is a\
  slave.
* `$CHILDREN` -> list of IPs and ports of the child nodes of the server who\
  initiated the event. For master-slave setups, this will be a list of slave\
  servers if the initiating server is a master.

The expanded variable value can be an empty string if no servers match the\
variable's requirements. For example, if no masters are available `$MASTERLIST`\
will expand into an empty string. The list-type substitutions will only contain\
servers monitored by the current monitor.

```
script=/home/user/myscript.sh initiator=$INITIATOR event=$EVENT live_nodes=$NODELIST
```

The above script could be executed as:

```
/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
```

See section [Script example](#script-example) below for an example script.

Any output by the executed script will be logged into the MaxScale log. Each\
outputted line will be logged as a separate log message.

The log level on which the messages are logged depends on the format of the\
messages. If the first word in the output line is one of `alert:`, `error:`,`warning:`, `notice:`, `info:` or `debug:`, the message will be logged on the\
corresponding level. If the message is not prefixed with one of the keywords,\
the message will be logged on the notice level. Whitespace before, after or\
between the keyword and the colon is ignored and the matching is\
case-insensitive.

Currently, the script must not execute any of the following MaxCtrl\
calls as they cause a deadlock:

* `alter monitor` to the monitor executing the script
* `stop monitor` to the monitor executing the script
* `call command` to a MariaDB-Monitor that is executing the script

#### `script_timeout`

* Type: [duration](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide)
* Mandatory: No
* Dynamic: Yes
* Default: `90s`

The timeout for the executed script. The interval is specified as documented [here](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide). If no explicit unit\
is provided, the value is interpreted as seconds in MaxScale 2.4. In subsequent\
versions a value without a unit may be rejected. Note that since the granularity\
of the timeout is seconds, a timeout specified in milliseconds will be rejected,\
even if the duration is longer than a second.

If the script execution exceeds the configured timeout, it is stopped by sending\
a SIGTERM signal to it. If the process does not stop, a SIGKILL signal will be\
sent to it once the execution time is greater than twice the configured timeout.

#### `events`

* Type: enum
* Mandatory: No
* Dynamic: Yes
* Values: `master_down`, `master_up`, `slave_down`, `slave_up`, `server_down`, `server_up`, `lost_master`, `lost_slave`, `new_master`, `new_slave`
* Default: All events

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.

```
events=master_down,slave_down
```

The following table contains all the possible event types 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 gone down |
| server\_up   | A server with no assigned role has come up   |
| lost\_master | A server lost Master status                  |
| lost\_slave  | A server lost Slave status                   |
| new\_master  | A new Master was detected                    |
| new\_slave   | A new Slave was detected                     |

#### `journal_max_age`

* Type: [duration](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide)
* Mandatory: No
* Dynamic: Yes
* Default: `28800s`

The maximum journal file age. The interval is specified as documented [here](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-21-06/mariadb-maxscale-21-06-getting-started/mariadb-maxscale-2106-maxscale-2106-mariadb-maxscale-configuration-guide). If no explicit unit\
is provided, the value is interpreted as seconds in MaxScale 2.4. In subsequent\
versions a value without a unit may be rejected. Note that since the granularity\
of the max age is seconds, a max age specified in milliseconds will be rejected,\
even if the duration is longer than a second.

When the monitor starts, it reads any stored journal files. If the journal file\
is older than the value of *journal\_max\_age*, it will be removed and the monitor\
starts with no prior knowledge of the servers.

### Monitor Crash Safety

Starting with MaxScale 2.2.0, the monitor modules keep an on-disk journal of the\
latest server states. This change makes the monitors crash-safe when options\
that introduce states are used. It also allows the monitors to retain stateful\
information when MaxScale is restarted.

For MySQL monitor, options that introduce states into the monitoring process are\
the `detect_stale_master` and `detect_stale_slave` options, both of which are\
enabled by default. Galeramon has the `disable_master_failback` parameter which\
introduces a state.

The default location for the server state journal is in`/var/lib/maxscale/<monitor name>/monitor.dat` where `<monitor name>` is the\
name of the monitor section in the configuration file. If MaxScale crashes or is\
shut down in an uncontrolled fashion, the journal will be read when MaxScale is\
started. To skip the recovery process, manually delete the journal file before\
starting MaxScale.

### Script example

Below is an example monitor configuration which launches a script with all\
supported substitutions. The example script reads the results and prints it to\
file and sends it as email.

```
[MyMonitor]
type=monitor
module=mariadbmon
servers=C1N1,C1N2,C1N3
user=maxscale
password=password
monitor_interval=10000
script=/path/to/maxscale_monitor_alert_script.sh --initiator=$INITIATOR --parent=$PARENT --children=$CHILDREN --event=$EVENT --node_list=$NODELIST --list=$LIST --master_list=$MASTERLIST --slave_list=$SLAVELIST --synced_list=$SYNCEDLIST
```

File "maxscale\_monitor\_alert\_script.sh":

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| 56 |                     |
| 57 | #!/usr/bin/env bash |

initiator=""\
parent=""\
children=""\
event=""\
node\_list=""\
list=""\
master\_list=""\
slave\_list=""\
synced\_list=""

process\_arguments()\
{\
while \[ "$1" != "" ]; do\
if \[\[ "$1" =\~ ^--initiator=.\* ]]; then\
initiator=${1#'--initiator='}\
elif \[\[ "$1" =\~ ^--parent.\* ]]; then\
parent=${1#'--parent='}\
elif \[\[ "$1" =\~ ^--children.\* ]]; then\
children=${1#'--children='}\
elif \[\[ "$1" =\~ ^--event.\* ]]; then\
event=${1#'--event='}\
elif \[\[ "$1" =\~ ^--node\_list.\* ]]; then\
node\_list=${1#'--node\_list='}\
elif \[\[ "$1" =\~ ^--list.\* ]]; then\
list=${1#'--list='}\
elif \[\[ "$1" =\~ ^--master\_list.\* ]]; then\
master\_list=${1#'--master\_list='}\
elif \[\[ "$1" =\~ ^--slave\_list.\* ]]; then\
slave\_list=${1#'--slave\_list='}\
elif \[\[ "$1" =\~ ^--synced\_list.\* ]]; then\
synced\_list=${1#'--synced\_list='}\
fi\
shift\
done\
}

process\_arguments $@\
read -r -d '' MESSAGE << EOM\
A server has changed state. The following information was provided:

Initiator: $initiator\
Parent: $parent\
Children: $children\
Event: $event\
Node list: $node\_list\
List: $list\
Master list: $master\_list\
Slave list: $slave\_list\
Synced list: $synced\_list\
EOM

## print message to file

echo "$MESSAGE" > /path/to/script\_output.txt

## email the message

echo "$MESSAGE" | mail -s "MaxScale received $event event for initiator $initiator." <mariadb_admin@domain.com> |

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{% @marketo/form formId="4316" %}