Nomad Autoscaler Check Calculations

A scaling policy can include several checks all of which produce a scaling suggesting. The checks are executed at the same time during a policy evaluation and the results can conflict with each other. In a scenario like this, the autoscaler iterates the results the chooses the safest result which results in retaining the most capacity of the resource.

In a scenario where two checks return different desired directions, the following logic is applied.

• ScaleOut and ScaleIn => ScaleOut
• ScaleOut and ScaleNone => ScaleOut
• ScaleIn and ScaleNone => ScaleNone

In situations where the two same actions are suggested, but with different counts the following logic is applied, where the count is the absolute desired value.

• ScaleOut(10) and ScaleOut(9) => ScaleOut(10)
• ScaleIn(3) and ScaleIn(4) => ScaleIn(4)