Proxy requests from you.customdomain.com to the less-pretty ECR url like 12314141.dkr.ecr.us-west-2.amazonaws.com.
Example
docker run -p "8080:80" \
-e ECR_URL=12334456678.dkr.ecr.us-west-2.amazonaws \
-e REGISTRY_HOST=https://registry.example.com \
tozny/aws-ecr-proxy
How this works
HAProxy does not support logging to STDOUT/STDIN. The /var/log/haproxy/* files are symlinked to PID 1's STDOUT/STDIN. All HAProxy logs are sent to rsyslog running on port 8514. rsyslog then outputs the log to the haproxy logs, which are in turn output to STDOUT/STDIN. This is picked up by docker logs <container>. It's complicated because HAProxy doesn't support STDOUT logging, and Docker haproxy build doesn't support it either.