I came across an use case where I rapidly create/destroy ELBs for testing/demoing, and I needed those ELBs to support DNS wildcard.
That is, I wanted *.NAME-ID.REGION.elb.amazonaws.com to all land on the same ELB, so
that my haproxy that's sitting behind ELB can direct traffic to the right backend.
*.NAME-ID.REGION.elb.amazonaws.com doesn't actually work, so I needed to write
a custom DNS server where *.NAME-ID.REGION.elb.kohsuke.org would be valid CNAME
for NAME-ID.REGION.elb.amazonaws.com.
This project implements that custom DNS server.
You are welcome to use *.elb.kohsuke.org or run your own instance.
Launch an ELB, and wait for that to become available:
$ nslookup bar-1984295099.us-west-2.elb.amazonaws.com
Server: 192.168.250.1
Address: 192.168.250.1#53
Non-authoritative answer:
Name: bar-1984295099.us-west-2.elb.amazonaws.com
Address: 54.214.28.101
Now you can do this:
$ nslookup any.prefix.bar-1984295099.us-west-2.elb.kohsuke.org
Server: 192.168.250.1
Address: 192.168.250.1#53
Non-authoritative answer:
any.prefix.bar-1984295099.us-west-2.elb.kohsuke.org canonical name = bar-1984295099.us-west-2.elb.amazonaws.com.
Name: bar-1984295099.us-west-2.elb.amazonaws.com
Address: 54.214.28.101
You can run this program like the following:
sudo java -jar elb-dns.jar -b elb.example.com
Here is my Upstart config file:
description "Run ELB alias DNS"
author "Kohsuke Kwaguchi"
start on runlevel [2345]
stop on runlevel [!2345]
setuid root
respawn
script
java -jar /home/kohsuke/elb-dns-1.0-SNAPSHOT-jar-with-dependencies.jar -b elb.example.com
end script
In the parent DNS, you need to designate this custom DNS server as the delegation target:
elb.example.com NS host.where.I.run.dns.