Derived metric calculation in AppDynamics extensions — what are the assumptions and limitations?

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What are the assumptions and limitations for the derived metric calculation in AppDynamics Extensions?

Contents

• Assumptions
• Limitations

Assumptions

The assumptions made before the derived metrics calculation is initiated are:

• All the base metrics (in all different levels) are available (i.e, the metrics have been reported) for derived metrics calculation.
• For a derived metric to be calculated, all of its base metrics should have reported a valid Number. 

Limitations

The limitation when using the derived metrics calculator is: 

A derived metric cannot be reused in another derived metric

If a derived metric has to be calculated at different levels, each metric has to be specified separately in the list of metrics under the derivedMetrics section. For example, in the following metric tree: 

          Server1

              Queue

                  Queue1

                        RAM ops : 9

                        Hdd ops: 3

                        Total ops:12

                  Queue2

                        Total ops : 2

                        Hdd ops: 6

                        Total ops:8

                   Total ops: (12 +  8 = 20)

If the "Total ops" metric is required both at the queue level and server level, then the derivedMetrics section looks as follows:

- derivedMetricPath: “{x}|Queue|{y}|Total ops" //queue level Total ops
     formula: “{x}|Queue|{y}|RAM ops + {x}|Queue|{y}|Total ops”

- derivedMetricPath: “{x}|Total ops" //server level Total ops
     formula: “{x}|Queue|{y}|RAM ops + {x}|Queue|{y}|Total ops”

The queue level “Total ops” derived metric cannot be used for calculating the server level or any other level derived metric.