Configure monitor parameters to determine the service health

You can configure the following monitoring parameters to mark a service as DOWN on the basis of the monitoring probes.

Retries

Maximum number of probes to send to establish the state of a service for which a monitoring probe fails.

failureRetries

Number of retries that must fail, out of the number specified for the Retries parameter, for a service to be marked as DOWN. For example, if the Retries parameter is set to 10 and the Failure Retries parameter is set to 6, out of the ten probes sent, at least six probes must fail if the service is to be marked as DOWN.

alertRetries

Number of consecutive probe failures after which the appliance generates an SNMP trap called monProbeFailed.

Setting alertRetries to a Value Higher than the Retries Value

The alertRetries parameter, which specifies the maximum number of consecutive monitoring-probe failures after which the NetScaler appliance generates an SNMP trap called monProbeFailed, can now be set to a value higher than the Retries value (which specifies the maximum number of probes to send to establish the state of a service for which a monitoring probe failed). If the alertRetries value is higher than the Retries value, the SNMP trap is not sent until after the service is DOWN.

For example, if you set Retries to 3, alertRetries to 12, and the time interval to 5 seconds, the service is marked DOWN after 15 seconds (35), but no alert is generated. If the monitor probes are still failing after 60 seconds (125), the NetScaler appliance generates a monProbeFailed trap. If a probe succeeds at some time between 15 and 60 seconds, the service is marked UP and no alert is generated.

Setting the alertRetries value to a value higher than the Retries value helps in generating only genuine alerts and avoid false positives during scheduled restarts.

To set the alertRetries parameter value to a higher value than the Retries value by using the command line interface

At the command prompt, type:

add lb monitor <monitorName> [-retries <integer>] [-alertRetries <integer>]

Example:

add lb monitor monitor-HTTP-1 HTTP -retries 3 -alertRetries 12

To set the alertRetries parameter value to a higher value than the Retries value by using the GUI

  1. Navigate to Configuration > Traffic Management > Load Balancing > Monitors.
  2. Click Add to add a new monitor or select an existing monitor and click Edit.
  3. In the Retries box, type the value for the Retries parameter.
  4. In the SNMP Alert Retries box, type the value for the alertRetries parameter.

Configure monitor parameters to determine the service health