3.4.0 Matrix Server Administration Guide

Chapter 16: Advanced Topics 183

Custom Device Monitors

A custom device monitor is associated with a list of servers and a list of

virtual hosts configured on those servers. A custom device monitor can

be active on only one server at a time. On each server, the monitor uses a

probe mechanism to determine whether the service is active. The probe

mechanism is in one of the following states on each server: Up, Down,

Unknown, Timeout.

A custom device monitor also has an activity status on each server. This

status indicates the current activity of the monitor on the server. The

status can be one of the following: Starting, Active, Suspended, Stopping,

Inactive, Failure.

If it is necessary to fail over a virtual host associated with the custom

device monitor, Matrix Server looks for a server that meets both of these

conditions: the device monitor is active, and the device monitor probe

reports an Up status. If Matrix Server cannot locate a server where the

device is active and the probe status is Up, the virtual host will be left

inactive across the matrix.

The following example shows the state transitions for a custom device

monitor and its associated virtual host. The device monitor uses the

default values for autorecover, priority, and serial script ordering, and has

a Start and Stop script defined. The virtual host is configured with a

Primary network interface and two backup interfaces. There is also a

service monitor defined on the virtual host. It uses the default values for

autorecovery, priority, and serial script ordering and has Start and Stop

scripts defined.

The example begins at initial startup from an unknown state and the

virtual host is then located on the primary interface.

At time t1, the service monitor probe on the Primary reports a Down

status. The virtual host then becomes inactive all servers.

The virtual host cannot be active on the Primary server because the

service monitor is Down. It cannot become active on either of the backup

servers because the custom device monitor associated with the virtual

host is Inactive on these servers.