Load balancer based on CPU utilization

Question

How to setup a load balancer between 2 instances based on CPU utilisation?

If my first instance having more than 50% utilisation, second should load.

Answer 1

If you are using the Elastic Load Balancer service on AWS, then it is not possible to route based upon CPU Utilization.

From How Elastic Load Balancing Works - Elastic Load Balancing:

With Application Load Balancers, the load balancer node that receives the request evaluates the listener rules in priority order to determine which rule to apply, and then selects a target from the target group for the rule action using the round robin routing algorithm. Routing is performed independently for each target group, even when a target is registered with multiple target groups.

With Network Load Balancers, the load balancer node that receives the connection selects a target from the target group for the default rule using a flow hash algorithm, based on the protocol, source IP address, source port, destination IP address, destination port, and TCP sequence number. The TCP connections from a client have different source ports and sequence numbers, and can be routed to different targets. Each individual TCP connection is routed to a single target for the life of the connection.

With Classic Load Balancers, the load balancer node that receives the request selects a registered instance using the round robin routing algorithm for TCP listeners and the least outstanding requests routing algorithm for HTTP and HTTPS listeners.