How to register IP address for ECS task at startup so that other resources can find it

You can provide service discovery in ECS in two ways:

• Placing a load balancer in front of the service. ECS has direct integration with ELB (ALB, NLB, and CLB), and will automatically register and de-register each task from the ELB as needed.
• Cloud Map. This does not involve an ALB, instead ECS will add each task as a discoverable item in Cloud Map. This can be done either by DNS, in an private Route 53 hosted zone, or via API, or both, depending on how you configure the Cloud Map namespace.