App Service autoscale strange behaviour

Piotr Zbyszyński 1

App Service autoscaling behaves strange recently. I have scaling rules set up based on time of day.

I can not set up overlapping rules, for example rule A: from 08:00 till 11:00, rule B: from 11:00 till 14:00. After saving this rules are automatically converted to A: 08:00 till 10:59 and B: 11:00 till 14:00.
Then autoscaling probe runs on 10:59 and decides that there is no applicable rule and scales everything down (using default rule). And on 11:00 it finds applicable rule B and scales everything up again.

I am pretty sure it just started to happen few days ago. Before everything was fine. Any advice how to prevent autoscaling to fallback to default autoscale rule between rules A and B?

Ryan Hill 25,666 Reputation points Microsoft Employee

2021-10-15T14:03:28.633+00:00

Where you able to able to scale A to 11:00 and B at 11:00 before? If you could before and not now, then this may have been a portal update. Having said that, let me see if I can repro your issue. Just make sure everything is inline, what region are deploying to? Does rule A scale instances up and rule B scale back down? Or do the rules scale out? Are there any memory/CPU thresholds in place?
Piotr Zbyszyński 1 Reputation point

2021-10-15T14:30:21.853+00:00

Region is West Europe. I am pretty sure not so long ago everything was fine. I am not sure if I was able to create overlapping rules, but there was no scaling back using default rule in-between rules

Both rules scales out. There is CPU thresholds but rule A has greater minimum instance count then default rule, and rule B has greater minimum instance count then rule A. When CPU threshold hits it just scales out even more, between minimum end maximum instance count, so it should be no factor it his case
Piotr Zbyszyński 1 Reputation point

2021-10-15T14:41:35.597+00:00

Here is log excerpt from concrete case. Rule A is till 12:19 (minimum instance: 3) and rule B starts an 12:20 (minimum instance: 4)

Scaling down using default rule:

,"profileEvaluationTime":"10/15/2021 12:19:19 PM","evaluationResult":"Profile is applicable for current time","profile":"{\"name\":\"Auto created scale condition\",\"for\":\"Weekdays\"}","profileSelected":"True"}}
"currentInstanceCount":"3","minimumInstanceCount":"2","maximumInstanceCount":"2","defaultInstanceCount":"2"}}
"currentInstanceCount":"3","newInstanceCount":"2","shouldUpdateInstance":"True","reason":"Current instance count is above maximum instance count"}}

And then after few minutes (probably to cool down):

"profileEvaluationTime":"10/15/2021 12:25:19 PM","evaluationResult":"Profile is applicable for current time","profile":"Weekdays afternoon","profileSelected":"True"}}
"currentInstanceCount":"2","minimumInstanceCount":"4","maximumInstanceCount":"5","defaultInstanceCount":"4"}}
"currentInstanceCount":"2","newInstanceCount":"4","shouldUpdateInstance":"True","reason":"Current instance count is below minimum instance count"}}