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The NetScaler appliance has a set of default monitors that are automatically bound to the respective service as soon as you create the service. For example, the tcp-default monitor is bound to all TCP services and the ping-default monitor is bound to all non-TCP services. The NetScaler appliance allows multiple monitors to be bound to a service. These monitors, by default, monitor the service they are bound to, but can be configured to monitor any destination IP address, port or both. A practical example of this is a Web server which makes a call to a backend database server where, if the database server fails, you also want the Web server to be marked as Down. To be precise, the health of one service is tied to the health of another potentially related service. A service monitoring threshold is set for each service which when combined with the weight of the monitor that is bound to the service, helps you to control how many monitors must fail before you consider the service as Down. If the monitor bound to the service satisfies the threshold, then it can be inferred that the service is Up. If any monitor fails to satisfy the threshold, then the service is considered as down. Mostly services fail when there are network connectivity issues between the backend servers on the port hosting the application, or connectivity issues between the NetScaler appliance and the backend servers, or if an SSL certkey is not bound to the virtual server etc. If too many services fail, then the performance of the NetScaler appliance will begin to degrade rapidly. To keep check on the performance degradation of the NetScaler appliance, administrators should constantly monitor the number of services that are down. The NSMonTest test helps administrators in this regard.

This test monitors the monitors that are bound to a service in the NetScaler appliance and reports the number of times the monitor bound to the service had hit the threshold limit and the number of times the monitor bound to the service was up/down.

For this test to run and report metrics, the NetScaler device should be configured to create a Syslog file in a remote Syslog server, where the details of all interactions with the NetScaler appliance will be logged. To know how to configure the Syslog server where this Syslog file should be created, Click here.

Outputs of the test : One set of results for the NetScaler appliance being monitored

Measurement	Description	Measurement Unit	Interpretation
monitor_hit_threshold	Indicates the number of times the monitor bound to the service had hit the threshold limit.	Number	This measure is a good check on the health of the service.
monitor_service_down	Indicates the number of times the monitor bound to the service was down.	Number
monitor_service_up	Indicates the number of times the monitor bound to the service was up.	Number