# Configuring the Xpand Monitor

This document describes how to configure the Xpand monitor for use\
with a Xpand cluster.

### Configuring the Monitor

Contrary to the other monitors of MaxScale, the Xpand monitor will\
autonomously figure out the cluster configuration and for each Xpand\
node create the corresponding MaxScale server object.

In order to do that, a *sufficient* number of "bootstrap" server instances\
must be specified in the MaxScale configuration file for the Xpand\
monitor to start with. One server instance is in principle sufficient, but\
if the corresponding node happens to be down when MaxScale starts, the\
monitor will not be able to function.

```
[Bootstrap1]
type=server
address=10.2.224.101
port=3306
protocol=mariadbbackend

[Bootstrap2]
type=server
address=10.2.224.102
port=3306
protocol=mariadbbackend
```

The server configuration is identical with that of any other server, but since\
these servers are *only* used for bootstrapping the Xpand monitor it is\
adviceable to use names that clearly will identify them as such.

The actual Xpand monitor configuration looks as follows:

```
[Xpand]
type=monitor
module=xpandmon
servers=Bootstrap1, Bootstrap2
user=monitor_user
password=monitor_password
monitor_interval=2s
cluster_monitor_interval=60s
```

The mandatory parameters are the object type, the monitor module to use, the\
list of servers to use for bootstrapping and the username and password to use\
when connecting to the servers.

The `monitor_interval` parameter specifies how frequently the monitor should\
ping the health check port of each server and the `cluster_monitor_interval`\
specifies how frequently the monitor should do a complete cluster check, that\
is, access the `system` tables of the Cluster for checking the Cluster\
configuration. The default values are `2000` and `60000`, that is, 2 seconds\
and 1 minute, respectively.

For each detected Xpand node a corresponding MaxScale server object will be\
created, whose name is `@@<Monitor-Name>:node-<id>, where _Monitor-Name_ is the name of the monitor, in this example`Xpand\` and *id* is the node id\
of the Xpand node. So, with a cluster of three nodes, the created servers\
might be named like.

```
@@Xpand:node-2`
@@Xpand:node-3`
@@Xpand:node-7`
```

Note that as these are created at runtime and may disappear at any moment,\
depending on changes happening in and made to the Xpand cluster, they\
should never be referred to directly from service configurations. Instead,\
services should refer to the monitor, as shown in the following:

```
[MyService]
type=service
router=readconnroute
user=service_user
password=service_password
cluster=Xpand
```

Instead of listing the servers of the service explicitly using the `servers`\
parameter as usually is the case, the service refers to the Xpand monitor\
using the `cluster` parameter. This will cause the service to use the Xpand\
nodes that the Xpand monitor discovers at runtime.

For additional details, please consult the monitor [documentation](https://mariadb.com/docs/maxscale/maxscale-archive/archive/mariadb-maxscale-23-02/mariadb-maxscale-23-02-monitors/mariadb-maxscale-2302-xpand-monitor).

<sub>*This page is licensed: CC BY-SA / Gnu FDL*</sub>

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