How can you launch ECS Fargate containers having a public DNS?

You can use ECS Service Discovery for registering your containers in a private DNS namespace - unfortunately this is not possible with public DNS.

But, what you can do, is to have a script

• fetch your containers' public IP after redeployment and
• upsert your public Route 53 record set with that IP.

In this article, we describe how to do exactly that by using a generic lambda function.

When I set up an ECS Fargate service for the first time, the setup wizard seems to have automatically (?) created a load balancer for me. I was able to access the web app that I created via the URL at Amazon ECS -> Clusters -> {my cluster} -> {my service} -> Target Group Name (under Load Balancing in the Details tab) -> {my target group} -> Load Balancer -> DNS Name

Although it's not free, normally if you want a public DNS name to an ECS service (fargate or EC2) you'd front it with a load balancer (which can also do SSL termination, if you so desire).

Because of that, AWS makes it easy to create a load balancer or add your service to an existing target group when you're setting up a service. I don't think you can change that after the fact, so you may need to recreate the service.

Finally, when you have a load balancer in front of the ECS service, you just need to set up a CNAME or an A ALIAS in Route53 (if you're using Route53) to direct a DNS name to that load balancer.

AWS has a walkthrough from 2016 on the AWS Compute Blog quickly describing how to set up an ECS service and expose it using an Application Load Balancer.

There is another path -- using ECS Service Discovery and AWS CloudMap, you can use an API Gateway. Your load balancing options are more limited, but API Gateways are billed based on usage rather than hours, so it can potentially save costs on lower-volume services. You can also use a single API Gateway in front of multiple ECS services, which some people are going to want to do anyway. This approach is less commonly employed, but might be the right path for some uses.