The Status Monitor (implemented as statd) is so general that it can also support other status-based network services and applications. The recovery of lost status information following a system crash is normally one of the most difficult factors in developing network applications. Thanks to the Status Monitor, it is more or less a routine task.
The Status Monitor acts as a central collection point for network status information. It is implemented as a daemon process and uses a simple protocol that allows applications to query the status of other systems with ease. Implementing the Status Monitor renders the network less prone to errors and helps to avoid situations where applications on different systems (or even on the same system) do not agree on the status of a computer. With many applications, such situations lead to inconsistencies.
To obtain information from the Status Monitor regarding changes to the network status, all systems that are to be monitored by the Status Monitor must be registered with the monitor by the application. If any of these systems fails (or, more precisely, if any of these systems restarts following a crash), all applications that have registered this system with the Status Monitor are informed about the restart by the monitor. The applications can then employ appropriate measures to update their status information.
This approach offers the following advantages:
- The time and code outlay resulting from cooperation with the Status Monitor must only be borne by applications that use status-based network services.
- Implementation of status-based network applications is simplified, because the Status Monitor shields the application developer from the complexity of the network.
For more information on the Status Monitor, see the description of statd in the section "Daemons".