I have an on-premises load balancer that I wish to use to distribute traffic on EC2s in an Autoscaling group(ASG).
When AWS's Elastic Load Balancer(ELB) registers an ASG as a target, during a scale-out,new instances are automatically registered to ELB to route traffic to.
Can the same functionality be achieved in any way with an on-prem load balancer?
There is in-built integration between Amazon EC2 Auto-Scaling and Elastic Load Balancers. The Auto Scaling systems knows how to modify Target Groups to add/remove instances. However, it has no knowledge about your on-premises load balancer.
You could use Amazon EC2 Auto Scaling lifecycle hooks to trigger additional code (that you write) to add/remove the instances to your own load balancer, but that would require an AWS Lambda function to communicate with the on-premises load balancer to update the configuration.
If you wanted to get the IPs of your target group you can do that do with an API call, and put that into your LB, but I think you may as well proxy calls from your LB to an ELB sitting on AWS which does the actual LoadBalancing. IMO there is way too much work and a lot could go wrong if you were to try and re-implement ELB features using Lambda functions.
