Horizontal Pod Autoscaling

I did a quick test of the HPA (Horizontal Pod Autoscaling) on OpenShift, here are some key findings:

  • Heapster metric is not near realtime, it is about 2 minutes delay in my test.
  • HPA only has one threshold to decide when to scale up or scale down. I think it makes sense, as pods normally take a few seconds to spin up. Really no point to have two thresholds.
  • HPA follows the common autoscaling practice – quick scale-up, slow scale-down.

Load test:  30 concurrent sessions/ 8000 requests/ 62.710 seconds duration.

Screen Shot 2017-11-02 at 10.01.22 AM.png

What I observed: HPA spins up a new pod when the CPU usage is over 80%. It is about 2 minutes delay. As when the scaling happens, the test has already completed for more than 1 minute. HPA took longer time to scale down. In my test, the pod has been running for about 5 minutes before gets terminated.

scale up

Screen Shot 2017-11-02 at 10.01.45 AM.png

scale down

Screen Shot 2017-11-02 at 10.07.20 AM.png




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