Establish connectivity between Nginx and a web application in ECS

Howdy,

I am trying to host a basic web application on ECS. I have a cluster set up for my web front end (nginx) and another cluster for my backend application (ctfd). I am attempting to have nginx act as a reverse proxy and forward HTTP traffic to my ctfd container which is listening on port 8000. Both applications are configured to use the same namespace which I've called "ctfd-api-dns". Both containers are hosted on fargate with the network mode set to avsvpc.

When I run my nginx task, it fails with the error:

nginx: [emerg] host not found in upstream "ctfd:8000" in /etc/nginx/nginx.conf:13

This error seems to indicate nginx is unable to resolve the address or reach the ctfd container running under the ctfd task.

Here is the nginx configuration being used by the nginx task running in the nginx cluster.

https://pastebin.com/raw/xzgkH2Nq

How can I establish connectivity between these two containers so that nginx acts as a reverse proxy for ctfd?

Cheers