NGinx and multiple docker containers but one subdomain - docker

Question

My Goal
I want to use a single NGinx docker container as a proxy.
I want it to respond to traffic on my domain: "sub.domain.com" and listen on port 80 and 443.
When traffic comes in on /admin I want it to direct all traffic to one docker container (say... admin_container:6000).
When traffic comes in on /api I want it to direct all traffic to another docker container (say... api_container:5500).
When traffic comes in on any other path (/anything_else) I want it to direct all traffic to another docker container (say... website_container:5000).
Some Helpful Context
Real quick, let me provide some context in case it's helpful. I have a NodeJS website running in a docker container. I'd like to also have an Admin section, created with ASP.NET Core that runs in a second docker container. I'd like both of these websites to share and make use of a single ASP.NET Core Web Api project, running in a third docker container. So, one NodeJS project and two ASP.NET Core projects, that all live on a single subdomain:
sub.domain.com/
Serves the main website
sub.domain.com/admin
Serves the Admin website
sub.domain.com/api
Serves API endpoints and handles Database connectivity
What I have So Far
So far I have the NGinX reverse proxy set up and a single docker container for the NodeJS application. Currently all traffic on :80 is redirected to 443. All traffic on 443 is directed to the NodeJS docker container, running privately on :5000. I'll admit I'm not great with NGinx and don't fully understand how this works.
The NGinx.conf file
worker_processes 2;
events { worker_connections 1024; }
http {
sendfile on;
proxy_buffer_size 128k;
proxy_buffers 4 256k;
proxy_busy_buffers_size 256k;
upstream docker-nodejs {
server nodejs_prod:5000;
}
server {
listen 80;
server_name sub.domain.com;
return 301 https://$host$request_uri;
}
server {
listen 443 ssl;
server_name sub.domain.com;
ssl_certificate /etc/nginx/ssl/combined.crt;
ssl_certificate_key /etc/nginx/ssl/mysecretkeyfile.key;
location / {
proxy_redirect off;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-Proto https;
proxy_set_header X-Forwarded-Ssl on;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Host $server_name;
proxy_pass http://docker-nodejs;
}
}
}
Quick Note: In the above code "nodejs_prod:5000" refers to the container who's name is "nodejs_prod" and listens on port 5000. I don't understand how that works, but it is working. Somehow docker is creating DNS entries in the private network, one for each container name. I'm actually using docker-compose.
My Actual Question: How will this NGinx.conf file look when I have 2 more websites (each a docker container). It's important that /admin and /api are sent to the correct docker containers, and not handled by the "catch all" location. I'm imagining that I'll have a "catch all" location which captures all traffic that DOESN'T START WITH /admin OR /api.
Thank you!

Answer 1

In your nginx config you want to add location rules, such as
location /admin {
proxy_pass http://admin_container:6000/;
}
location /api {
proxy_pass http://api_container:5500/;
}
This redirects /admin to admin_container port 6000, and /api to api_container and port 5500.
docker-compose creates a network between all it's containers. Which is why http://api_container:5500/ points to the container named api_container and the port 5500. This can be used for communication between containers. You can read more about it here https://docs.docker.com/compose/networking/