How to make docker compose use existing AWS subnet

Question

I have created an AWS VPC, subnet and security group and want to deploy my docker containers to these premade resources as a fargate ecs service.

However I don't know how to tell the service to use a premade subnet (it looks like it randomly picks a subnet from an 'allowed' list of subnets which is currently all subnets I have in my VPC

The below file correctly deploys to the desired vpc, cluster and security group, just not subnet:

version: '2'

x-aws-cluster: "Test Cluster"
x-aws-vpc: "vpc-02dffc2a8782579d4"
x-aws-security-group: "sg-02511658ffc184884"

services:
    nginx:
        image: nginx:1.19
        networks:
            - Backend-Access

networks:
    Backend-Access:
        external:
            name: sg-02511658ffc184884
        ipam:
            driver: default
            config:
            - subnet: subnet-0aeef680f1f9e5cda # this has no effect
            #- subnet: 172.31.4.0/24 also does not place the service in this subnet

I am running it using docker compose up -d (running it without -d gives a cluster does not exist error)

Answer 1

This is currently not possible and there is a GitHub issue open to ask for this specifically. If you could made your voice be heard there that's where we are consolidating this feedback. Thank you.

Answer 2

It is possible to make a subnet using the documented overlay method now and I solved it.

See the Github issue again. It was solved and closed two weeks ago.