NGINX proxy on ECS - Address already in use. How to do a dynamic port assignment to ALB and Security groups?



I am facing an issue when running NGINX as a proxy service with two tasks - they seem to be fighting over one port (nginx: [emerg] bind() to failed (98: Address in use)), which can be easily resolved by only having only one replica. Now, I am curious how I would approach this problem if I wanted more replicas which are being load balanced by the ALB. Setting a dynamic port 0 means that there is a big chance that the Security Group will deny access to it, as only a few ranges are allowed.

1 Answer


Running multiple instances (tasks) of a service on a single host in Amazon ECS can certainly lead to port conflicts if not configured appropriately, especially when you're dealing with standard HTTP/S ports. If you’re running NGINX as a reverse proxy in ECS, here's how you might handle dynamic port mappings, while still ensuring compatibility with the Application Load Balancer (ALB) and security groups.

Regards, Andrii

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answered 6 months ago
  • Hey Andrii, are you missing a link in the answer?

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