The probe uses the nslookup command to query the health of DNS. Before the probe actually queries the DNS server, a check is made to confirm that network resources are configured in the same resource group as the DNS data service. If no network resources are configured, an error message is logged, and the probe exits with failure.
The probe executes the following steps.
Run the nslookup command using the time-out value that the resource property Probe_timeout specifies.
The result of this nslookup command can be either failure or success. If DNS successfully replied to the nslookup query, the probe returns to its infinite loop, waiting for the next probe time.
If the nslookup fails, the probe considers this scenario a failure of the DNS data service and records the failure in its history. The DNS probe considers every failure a complete failure.
Based on the success/failure history, a failure can cause a local restart or a data service failover. “Sun Cluster Data Service Fault Monitors” in Sun Cluster Data Services Planning and Administration Guide for Solaris OS further describes this action.