Amazon Elastic Container Service (ECS) health checks give you more control over monitoring the health of your tasks and improve the ability of the ECS service scheduler to ensure your services are healthy.If health checks are not configured for this container in its task definition, then it reports the health status as UNKNOWN.
Using the HEALTH CHECK command, you can define which parameters to monitor for each container in your Task Definition. Running tasks (groups of running containers) are now assigned a health status based on the health of their essential containers, and the task’s health status is integrated with the ECS service scheduler to automatically redeploy unhealthy tasks and conduct rolling updates of services. You can check the health status of your tasks and containers in the ECS Console or with the ECS DescribeTasks API.
Additional Reference: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#container_definition_healthcheck