get_ecs_service_instances.sh

function get_ecs_service_instances () {
  local cluster_name=$1
  local service_name=$2
  local tasks
  local container_arns
  local ec2_instance_ids

  echo "Cluster: ${cluster_name}"
  echo "Service: ${service_name}"
  echo "EC2 instances:"

  # Get tasks
  tasks=$(aws --output json \
    ecs list-tasks \
    --cluster "${cluster_name}" \
    --service-name "${service_name}" | \
    jq '.taskArns[]' | sed 's@.*task/@@' | tr -d '"' | tr "\n" " ")

  # Get container arn and host port
  container_arn_ports=$(aws --output json \
    ecs describe-tasks \
    --cluster "${cluster_name}" \
    --tasks ${tasks} | \
    jq '.tasks[] | [.containerInstanceArn, .containers[].networkBindings[].hostPort | tostring] | join(" ")' | tr -d '"')

  # Get EC2 instance ip and port
  echo "${container_arn_ports}" | \
  while read container_arn host_port
  do
    # get instance id
    ec2_instance_id=$(aws --output json \
      ecs describe-container-instances \
      --cluster "${cluster_name}" \
      --container-instances "${container_arn}" | \
      jq '.containerInstances[].ec2InstanceId' | tr -d '"')
    # get instance private ip
    ec2_instance_private_ip=$(aws --output json \
    ec2 describe-instances \
    --instance-ids ${ec2_instance_id} | \
    jq '.Reservations[].Instances[].PrivateIpAddress' | tr -d '"')
    echo "${ec2_instance_private_ip}:${host_port}"
  done
}