Multiple docker containers as web server on a single IP

Question

I have multiple docker containers on a single machine. On each container is running a process and a web server that provides an API for the process.

My question is,

Answer 1

Only a single process is allowed to be bound to a port at a time. So running multiple containers means each will be exposed on a different port number. Docker can do this automatically for you by using the "-P" attribute.

sudo docker run -P -t -i <yourname>/<imagename>

You can use the "docker port" and "docker inspect" commands to see the actual port number allocated to each container.

Answer 2

You can either expose multiple ports, e.g.

docker run -p 8080:80 -t -i <yourname>/<imagename>
docker run -p 8081:80 -t -i <yourname1>/<imagename1>

or put a proxy ( nginx, apache, varnish, etc.) in front of your API containers.

Update:

The easiest way to do a proxy would be to link it to the API containers, e.g. having apache config

RewriteRule ^api1/(.*)$ http://api1/$1 [proxy]
RewriteRule ^api2/(.*)$ http://api2/$1 [proxy]

you may run your containers like this:

docker run --name api1 <yourname>/<imagename>
docker run --name api2 <yourname1>/<imagename1>
docker run --link api1:api1 --link api2:api2 -p 80:80 <my_proxy_container>

This might be somewhat cumbersome though if you need to restart the api containers as the proxy container would have to be restarted either (links are fairly static at docker yet). If this becomes a problem, you might look at approaches like fig or autoupdated proxy configuration : http://jasonwilder.com/blog/2014/03/25/automated-nginx-reverse-proxy-for-docker/ . The later link also shows proxying with nginx.

Update II:

In a more modern versions of docker it is possible to use user defined network instead of the links shown above to overcome some of the inconveniences of the deprecated link mechanism.