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I have an auto-scaling group with two target scaling policies, one is based on SQS backlog and another on CPU-Utilization. I have initially set the capacities at minimum-1,desired-1,maximum-4. During the scale-out process, my desired capacity changed to 2 automatically. Now all the messages in the queues were successfully processed and the two scaling processes are requesting the ASG to scale in. But, the desired capacity is still at 2 and is not coming down. Is there a logic that I am missing? or do I need to do it manually? enter image description here

DC_Valluru
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  • Can you please show us your Scale-In Policies? – John Rotenstein Jun 17 '21 at 07:50
  • @JohnRotenstein hi I have uploaded the image with two target tracking policies. One is base on a custom metric and another is based on CPU utilization. – DC_Valluru Jun 17 '21 at 07:57
  • You seem to have two Target Tracking policies -- one related to Average CPU of EC2 instance(s), and the other related to what appears to be a custom metric? It isn't clear what would happen if the two policies conflict with each other. I would recommend choosing only one Target Tracking metric. – John Rotenstein Jun 17 '21 at 08:02
  • As per AWS documentation, a conflict would not occur between two target scaling policies as AWS tries to provide the maximum number of instances after comparing the two policies. Now the scale-in alarms for both the policies are active and still, the desired capacity is not coming down to its original set value. – DC_Valluru Jun 17 '21 at 08:05
  • Well, perhaps one policy is wanting 2 instances and the other policy is wanting 1 instance. From what you say, it would provide "the maximum number of instances", which would be 2. – John Rotenstein Jun 17 '21 at 08:07
  • Well, the case is, now both the policies are requesting for scale-in of ASG. But, when the scale-out happened the desired capacity changed to 2 from 1 and now is not changing back. – DC_Valluru Jun 17 '21 at 08:09
  • Can you show us the Scaling History that is saying that both policies want a Desired Capacity of 1? – John Rotenstein Jun 17 '21 at 08:11
  • @JohnRotenstein Hi, The problem finally got solved. It was a problem due to elastic beanstalk upgrade failure. Once I sorted that issue, the desired capacity automatically came down. – DC_Valluru Jun 17 '21 at 10:00

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