Multiple docker containers accessible by nginx reverse proxy - nginx

Question

I'd like to run multiple docker containers on one host VM which would be accessible through only one domain. I wanted to use request url to differentiate between containers.
To achieve this I'm trying to set nginx server as reverse proxy and run it in the container also listening on port 80.
Let's say I have two containers running on port 3000 and 4000.
The routing would be following:
docker-host.example.com/3000 -> this will access container exposing port 3000
docker-host.example.com/4000 -> this will access container exposing port 4000
The thing is I'm currently stack even with trying to define static rule for such reverse proxy.
It works fine without any location:
upstream application {
server <docker container>:3000;
}
server {
listen 80;
location / {
proxy_pass_header Server;
proxy_set_header Host $http_host;
proxy_redirect off;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Scheme $scheme;
proxy_pass http://application/;
}
}
But when I add port location and try to access it using localhost:{nginx port}/3000/
upstream application {
server <docker container>:3000;
}
server {
listen 80;
location /3000/ {
proxy_pass_header Server;
proxy_set_header Host $http_host;
proxy_redirect off;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Scheme $scheme;
proxy_pass http://application/3000/;
}
}
It seems that first resource (main html) is requested correctly, but any other depending resource (for example js or css needed for this site) is missing.
If I examine request for those resources I have in logs:
09:19:20 [error] 5#5: *1 open() "/etc/nginx/html/public/css/fonts.min.css" failed (2: No such file or directory), client: 172.17.0.1, server: , request: "GET /public/css/fonts.min.css HTTP/1.1", host: "localhost:8455", referrer:"http://localhost:8455/3000/"
So request url is http://localhost:8455/public/css/fonts.min.css
Instead of http://localhost:8455/3000/public/css/fonts.min.css
Could I ask you for any suggestions ? Is this scenario possible ?

Answer 1

You can select a docker container per port, your example:
http://example.com:4000/css/fonts.min.css
http://example.com:3000/css/fonts.min.css
But there is another approach that I like more, because I think it is clearer, access to a docker container by domain name, e.g:
http://a.example.com/css/fonts.min.css
http://b.example.com/css/fonts.min.css
Whichever you choose, there is a project in github that helps you to implement docker multi-container reverse proxy: https://github.com/jwilder/nginx-proxy
I've written an example using docker-compose for a similar scenario at: http://carlosvin.github.io/posts/reverse-proxy-multidomain-docker/