Docker Swarm Service Discovery in index.html - docker

Question

I have two express web apps (server and client) that I am using docker-compose and / or docker stack to deploy in docker swarm. They both have APIs that communicate with each other via their service names, as they are both connected to the same overlay network. A snippet of the config file that client uses to make REST calls to server follows:
"server": {
"url":"http://server:8085",
"endpoints": {
"devices": "/devices",
"temperature": "/temperature",
"mock": "/mock"
}
}
Finding the server by host name is no issue from the node side as it is running directly inside the docker container. However, both express apps serve web pages. Both client and server's css and js dependencies are almost identical and I do not want to write each stylesheet twice. I'd rather server a single copy from server that both index.html files from server and client can use.
In the index.html, of server I can use relative paths because the host is the same, and thus implied. But, in index.html of client I need a fully qualified url. Something like:
<link rel="stylesheet" href="http://server:8085/style.css">
Obviously this would not work once I serve index.html from client to a browser because the browser is going to look for http://server over the internet, rather than in the docker overlay network for these services.
I thought about downloading the files in client's node app before it serves index.html but, that's not the cleanest solution.
Is there an elegant way to accomplish this without binding server to a static ip / domain or programmatically downloading these files first?

Answer 1

If your external users' browser needs to access files on client and server then you will need to publish both Swarm Services to the external IP's of the Swarm nodes, and then put those IP's in DNS names or an external LB, and only use those URL's for remote connectivity.
When you do that, you'll likely need to bind both services to the same port (443). If that's the case, then you also need another layer of proxy that routes traffic to the proper container based on path or DNS name.
Both http://proxy.dockerflow.com/ and https://traefik.io/ work for that purpose.