reproxy maps var/run/docker.sock into its container using a volume so that it can query the settings of the other containers.
I can use docker context ecs and docker compose to bring up a docker composer file as a cluster on AWS ECS on Fargate.
I get the following error in the reproxy log
2021/06/17 13:55:42.903 [ERROR] failed to fetch running containers: can't list containers: failed connection to docker socket: Get "http://localhost/v1.22/containers/json": dial unix /var/run/docker.sock: connect: no such file or directory
And this is because the line :

 volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro

is not allowed. We cannot bind host path /var/run/docker.sock as a mount point.

it is discussed here: https://stackoverflow.com/questions/53759932/aws-fargate-volumes

This may be well beyond the scope of reproxy.