How can I alias containers running a UDP service on ECS?

Question

I'm attempting to run logstash in a container against ECS, which will listen for log messages over UDP.

I want my apps to be able to send messages to e.g. logging.mydomain.com without needing to know the underlying IP(s) which may change.

Normally I would CNAME an ELB, but ELB does not support UDP. Do I need to do some kind of service discovery here or is there something simpler I can do?

Answer 1

I would recommend using Amazon Route 53 DNS round robin to solve this problem.

The pieces are:

• A Lambda function attached to the Cloudwatch Events stream for your logstash service in ECS. This lambda function will be invoked whenever there is a task state change, and so it runs when a new logstash task is started or stopped and updates the Route 53 record
• When your application resolves the dns record it will be given one of the IP addresses round robin style and communicate directly with the instance hosting the logstash container, using its IP.
• Your ECS service will need to have a statically assigned host port rather than a dynamic port.

There is a reference architecture that described this in more detail, and has sample code for you: https://aws.amazon.com/blogs/compute/service-discovery-for-amazon-ecs-using-dns/