2. Sensing (Monitoring) the Service State : 2.1 Monitoring Approaches : 2.1.7 Triggering the Scale Event : Uncontrolled Scaling Uncontrolled Scaling
When triggering a scale event, we cannot decide to increase capacity when our threshold exceeds or falls below the set point. This results in a Ping-Pong effect, where the infrastructure is constantly scaling out and scaling back as it seeks the set point for our triggering metric. Depending on the instability of the system, this can result in significant overshoot while seeking the set point, where the system increasingly overprovisions resources and then decreases them back and forth, resulting in an ever-increasing problem. The following figure provides an illustration of uncontrolled scaling.
Figure 6. Uncontrolled Scaling
This constant expansion and contraction of resources with today’s technology places an undesirable load on the infrastructure and can ultimately result in further degradation of the service.