ECS container instances have attributes of 'runningTasksCount' and 'pendingTasksCount'. See Boto3 docs here: http://boto3.readthedocs.io/en/latest/reference/services/ecs.html#ECS.Client.describe_container_instances REST API docs here: http://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_DescribeContainerInstances.html#API_DescribeContainerInstances_ResponseSyntax