Can not access server running in a docker container on an EC2 with a load balancer via a subdomain pointing at a loadbalancer.

Question

I currently have a subdomain pointing at a load balancer. I have created a SSL/TLS certificate that includes the domains,  `api.domain.dev` and `domain.dev`. I have added the CNAMES values accordingly to the domain DNS records.

I have also added a CNAME with HOST:`api.domain.dev` and ANSWER: the DNS url of the load balancer.

The load balancers have an HTTP and HTTPS listener on ports 80 and 443 respectively. The load balancer is associated with 2 subnets with `Auto-assign public IPv4 address` set to true.

Not sure what configuration is causing the issue.

The server is up and running. I can ssh into the EC2 and send requests to localhost:5000/api.

GK · Answer

Hi

**[Target Port](https://repost.aws/questions/QUIybsCB2FTuSdi9vgZjVs-g/how-to-configure-aws-application-load-balancer-to-forward-requests-to-ec2-flask-5000-ports)** Ensure the target group in your load balancer is configured to forward traffic to the correct port on your EC2 instance where the Docker container is listening. Double-check that the target port in the load balancer matches port 5000 where your server listens (based on your localhost:5000/api access).

**[Security Group](https://000015.awsstudygroup.com/2-prerequiste/2.2-createsg/)**  Verify that the security group of your EC2 instance allows traffic on port 5000 (or the container port) from the load balancer's security group.

**[Health Checks](https://docs.aws.amazon.com/AmazonECS/latest/bestpracticesguide/load-balancer-healthcheck.html)** Verify the load balancer health checks are functioning correctly.

References: https://stackoverflow.com/questions/66864290/aws-ec2-how-to-setup-load-balancer-to-match-docker-container-on-ec2-instance

https://aws.amazon.com/blogs/compute/how-to-quickly-setup-an-experimental-environment-to-run-containers-on-x86-and-aws-graviton2-based-amazon-ec2-instances-effort-to-port-a-container-based-application-from-x86-to-graviton2/

Can not access server running in a docker container on an EC2 with a load balancer via a subdomain pointing at a loadbalancer.

Add your answer

Relevant content