Does AWS Fargate docker image with express app listening and waiting for requests consume cpu?

Question

I configured an AWS Fargate cluster with a docker image that runs nodejs express app and listens on port 80. Now I can browse to the public IP and successfully the request is handled by AWS Fargate.

Is it right that the docker container now is running and still waiting for requests? Isn't it consuming CPU and so I have to pay as long as the docker container is running?

Do I have to build a docker image that just handles a single request and exits to be really serverless?

Thank you

Answer 1

Is it right that the docker container now is running and still waiting for requests? Isn't it consuming CPU and so I have to pay as long as the docker container is running?

Yes, that's how ECS Fargate works. It's really no different from running a docker container on your local computer. It has to be up and running all the time in order to handle requests that come in.

Do I have to build a docker image that just handles a single request and exits to be really serverless?

The term "serverless" is a vague marketing term and means different things depending on who you ask. Amazon calls ECS Fargate serverless because you don't have to manage, or even know the details of, the server that is running the container. In contrast to ECS EC2 deployments, where you have to have EC2 servers up and running ahead of time and ECS just starts the containers on those EC2 servers.

If you want something that only runs, and only charges you, when a request comes in, then you would need to reconfigure your application to run on AWS Lambda instead of ECS Fargate.