This module will track IP changes on AWS RDS instances and update a given (NLB) target-group with theses IP addresses.

Most of the python code comes from [1], inspired by [2]

Architecture:

___________________________
| RDS Events subscription |
~~~~~~~~~~~~~~~~~~~~~~~~~~~
            |
            |       _______     __________     ____________________
            +------>| SNS |---->| Lambda |---->| NLB target-group |
                    ~~~~~~~     ~~~~~~~~~~     ~~~~~~~~~~~~~~~~~~~~

When invoked, the lambda function will:

• Lookup IP addresses from given FQDN list
• check target-group registered IPs (target health isn't taken into account)
• add/remove IP from target group so they match the FQDN list.

Prerequisites:

This terraform code doesn't create load-balancer resources nor its components (listener, target-group). You'll have to declare them separately

It basically replaces the function that aws_lb_target_group_attachment resources holds when attaching to static ip addresses.

[1] https://github.com/aws-samples/hostname-as-target-for-elastic-load-balancer

[2] https://aws.amazon.com/blogs/networking-and-content-delivery/hostname-as-target-for-network-load-balancers/