Amazon Elastic Container Service (ECS) now publishes Elastic Load Balancer(ELB) lifecycle events for services attached to multiple load balancer target groups. ECS will emit service events when tasks are successfully registered or de-registered in target groups or in case of errors in the registration process. This enables you to track the progress of attaching your service to multiple target group and easily troubleshoot errors through events in the ECS service event stream as part of the update and describe service API responses as well as in the ECS Management Console. This functionality has already been available for services attached to a single target group but is now available for services attached to multiple target groups as well.
Source:: Amazon AWS