Docker compose ECS integration: load balancer is of type application, project require a network

Question

I have a docker-compose.yml file as follows:

version: "3.8"
x-aws-loadbalancer: "arn:aws:elasticloadbalancing:my-load-balancer"
services:
  fastapi:
    image: username/auth:FastAPI
    x-aws-pull_credentials: "arn:aws:secretsmanager:us-west-2:creds"
    build: FastAPI
    ports:
      - "5555:5555"
  nginx:
    image: username/auth:nginx
    x-aws-pull_credentials: "arn:aws:secretsmanager:us-west-2:creds"
    build: nginx
    ports:
      - "80:80"
    depends_on:
      - fastapi
networks:
  default:
    external: true
    name: my-sg

But when attempting to integrate this with ECS using docker compose up I receive the error:

load balancer "arn:aws:elasticloadbalancing:my-load-balancer" is of type application, project require a network

I have also tried providing a vpc using the top-level x-aws-vpc property and received the same error.

What

Answer 1

It's because you are using port 5555, which docker-compose can't know is being uses for HTTP, so it makes the assumption that you need a network load balancer since Application Load Balancers only support HTTP.

Per the documentation for ECS docker-compose integration:

If services in the Compose file only expose ports 80 or 443, an Application Load Balancer is created, otherwise ECS integration will provision a Network Load Balancer. HTTP services using distinct ports can force use of an ALB by claiming the http protocol with x-aws-protocol custom extension within the port declaration:

So, just going by that example at the documentation I linked, I would try changing your FastAPI service declaration to the following:

  fastapi:
    image: username/auth:FastAPI
    x-aws-pull_credentials: "arn:aws:secretsmanager:us-west-2:creds"
    build: FastAPI
    ports:
      - "5555:5555"
        x-aws-protocol: http

Or maybe change it to the following, to more closely match the example in the documentation:

ports:
  - target: 5555
    x-aws-protocol: http