If I remove an instance from ELB via Instances tab, "Remove from Load Balancer", how does this affect my autoscaling group? For example, my autoscale group has 3 instances in it, and 3 InSErvice behind ELB. If i remove one of those instances from the load balalncer, I still see 3 active in my autoscaling group. Shouldn't the autoscaling group attach an additional instance to the load balancer?
1 Answers
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Auto Scaling groups will only scale-out or scale-in based on Amazon CloudWatch alarms or via calls to the API that change the Desired Capacity of the group.
Auto Scaling will also terminate unhealthy instances, as detected by a System Status Check or if it is configured to use the ELB Health Check.
Auto Scaling does not monitor which instances are attached to the Load Balancer. In fact, you should not detach an instance in this manner because Auto Scaling assumes that it is managing the relationship between the Load Balancer and instances that it launches.
If you intention is to remove a specific instance from an Auto Scaling group and to have it replaced, use the DetachInstances API call and indicate whether you want the instance to be replaced.
