nginx as a docker upstream proxy with maps - nginx

Question

Trying to use docker to setup a bunch of apps behind a proxy using the nginx maps option for ease of configuration with a large number of backend applications.
The trouble I'm running into is the container won't resolve the addresses that I've given it with links.
I've tried using dnsmasq but that was troublesome, and didn't give me a working resolution.
Any suggestions?
nginx.conf:
events {
worker_connections 1024;
}
http {
map $hostname $destination {
hostnames;
default host1:81;
host1.test.local host1:81;
host2.test.local host2:82;
host3.test.local host3:83;
}
server {
location / {
proxy_pass http://$destination/;
}
}
}
docker-compose.yml:
webproxy:
build: nginx:latest
ports:
- "80:80"
volumes:
- nginx.conf:/etc/nginx/nginx.conf
links:
- "host1:host1"
- "host2:host2"
- "host3:host3"
host1:
image: nginx:latest
ports:
- "81:80"
volumes:
- host1/index.html:/usr/share/nginx/html/index.html
host2:
image: nginx:latest
ports:
- "82:80"
volumes:
- host2/index.html:/usr/share/nginx/html/index.html
host3:
image: nginx:latest
ports:
- "83:80"
volumes:
- host3/index.html:/usr/share/nginx/html/index.html
Error I constantly get:
webproxy_1 | 2015/07/14 16:44:11 [error] 5#0: *1 no resolver defined to resolve host1, client: 10.0.2.2, server: , request: "GET / HTTP/1.1", host: "host2.test.local:8281"
webproxy_1 | 10.0.2.2 - - [14/Jul/2015:16:44:11 +0000] "GET / HTTP/1.1" 502 181 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:39.0) Gecko/20100101 Firefox/39.0"