The sample application implements a basic fault monitor to monitor the reliability of the DNS resource (in.named).
The fault monitor consists of the following elements:
dns_probe, a user-defined program that uses nslookup to verify that the DNS resource that is controlled by the sample data service is running. If DNS is not running, this method attempts to restart it locally, or depending on the number of restart attempts, requests that the RGM relocate the data service to a different node.
dns_monitor_start, a callback method that starts dns_probe. The RGM automatically calls dns_monitor_start after the sample data service is brought online if monitoring is enabled.
dns_monitor_stop, a callback method that stops dns_probe. The RGM automatically calls dns_monitor_stop before bringing the sample data service offline.
dns_monitor_check, a callback method that calls the Validate method to verify that the configuration directory is available when the PROBE program fails over the data service to a new node.