Health monitoring - dnaHealthMonitor

If a failure occurs, you should follow a certain set of principles and logic to ensure that your system maintains a good health state.

When a AVEVA Enterprise SCADA Service is running, any failure must be dealt with in an orderly and well-defined manner. Such failures may be as complex as a process failing, or as simple as a disk filling to capacity. For example, in such failure conditions, the service may require the following logic:

• If the service is not arbitrated, identify the failure to the user and to the event log.

• If the service is arbitrated, determine if there is a partner computer.

• If there is no partner, then identify the failure to the user and to the log.

• If the service is arbitrated and there is a partner, determine if the partner can take control of the service.

• If the partner can take control of the service, attempt to failover, shutdown and log the problem experienced by the service.

• If the partner is not in a state that it can take control of the service, log the message and wait until the partner is ready to take control of the service. When the partner is ready, take the actions of failing over, shutting down and logging the problem.

The dnaHealthMonitor is used as a single decision maker to execute the above logic. This ensures that individual processes do not need to code the above logic, but instead need only tell the dnaHealthMonitor that a critical problem exists.

This generalized mechanism is typically used by such entities as the Process Monitor facilities, the Arbitration facilities, and the computer health monitoring facilities (disks, physical memory, and so forth). When any such facility identifies a critical problem with the current service, they will signal the dnaHealthMonitor to take appropriate actions. If the problem resolves itself (for example, the user cleans up to a disk that was full), then the dnaHealthMonitor can be advised that the critical problem is no longer in effect.

Note: Each AVEVA Enterprise SCADA Service will start an instance of the dnaHealthMonitor.