Docker nginx proxy to host - nginx

Question

Short description:
Nginx running on docker, how to configure nginx so that it forwards calls to host.
Long description:
We have one web application which communicates to couple of backends (lets says rest1, rest2 and rest3). We are responsible for rest1.
Lets consider that I started rest1 manually on my pc and running on 2345 port. I want nginx (which is running in docker) to redirect all call torest1 to my own running instance(note, the instance is running on host, not any container and not in docker). And for rest2 and rest3 to some other docker node or may be some other server (who cares).
What I am looking for is:
docker-compose.yml configurations (if needed).
nginx configuration.
Thanks in advance.

Answer 1

Configure nginx like the following (make sure you replace IP of Docker Host) and save it as default.conf:
server {
listen 80;
server_name _;
location / {
proxy_pass http://<IP of Docker Host>;
index index.html index.htm;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/share/nginx/html;
}
}
Now bring up the container:
docker run -d --name nginx -p 80:80 -v /path/to/nginx/config/default.conf:/etc/nginx/conf.d/default.conf nginx

Answer 2

If you are using Docker Compose file version 3 you don't need any special config for docker-compose.yml file at all, just use the special DNS name host.docker.internal to reach a host service, as on the following nginx.conf example:
events {
worker_connections 1024;
}
http {
upstream host_service {
server host.docker.internal:2345;
}
server {
listen 80;
access_log /var/log/nginx/http_access.log combined;
error_log /var/log/nginx/http_error.log;
location / {
proxy_pass http://host_service;
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $realip_remote_addr;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_http_version 1.1;
proxy_set_header Connection "";
}
}
}

Answer 3

Solution 1
Use network_mode: host, this will bind your nginx instance to host's network interface.
This could result in conflicts when running multiple nginx containers: every exposed port is binded to host's interface.
Solution 2
I'm running more nginx instances for every service I would like expose to outside world.
To keep the nginx configurations simple and avoid binding every nginx to host use the container structure:
dockerhost - a dummy container with network_mode: host
proxy - nginx container used as a proxy to host service,
link dockerhost to proxy, this will add an /etc/hosts entry in proxy contianer - we can use 'dockerhost' as a hostname in nginx configuration.
docker-compose.yaml
version: '3'
services:
dockerhost:
image: alpine
entrypoint: /bin/sh -c "tail -f /dev/null"
network_mode: host
proxy:
image: nginx:alpine
links:
- dockerhost:dockerhost
ports:
- "18080:80"
volumes:
- /share/Container/nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
default.conf
location / {
proxy_pass http://dockerhost:8080;
This method allows us to have have automated let's encrtypt certificates generated for every service running on my server. If interested I can post a gist about the solution.

Answer 4

server {
listen 80;
server_name localhost;
location / {
proxy_pass http://host.docker.internal:3000;
}
}
Docker expose host address is host.docker.internal in Mac os

Answer 5

There a couple of things you have to keep in mind:
Docker compose (from version 3) by default uses the service name as hostname for inter container networking
Nginx need to know the upstream first
I strongly recommend mounting the default.conf directly into your docker-compose.yml.
Lastly you have to dockerize your backend to make use of docker internal networking.
An example repo where I use nginx and docker-compose in a full-stack project: https://gitlab.com/datails/api.
The following example have some prerequisites:
you have a folder structure like:
- backend/
- frontend/
- default.conf
- docker-compose.yml
Secondly the backend and front-end dit have a Dockerfile that exposes an application on port 3000.
Example default.conf:
upstream backend {
server backend:3000;
}
upstream frontend {
server frontend:3000;
}
server {
listen 80;
location /api {
proxy_pass http://backend;
}
location / {
proxy_pass http://frontend/;
}
}
Example docker-compose.yml:
version: '3.8'
services:
nginx:
image: nginx:1.19.4
depends_on:
- server
- frontend
volumes:
- ./nginx.conf:/etc/nginx/conf.d/default.conf
ports:
- '8080:80'
Then make sure you have your backend dockerized and called (in this case) backend as a service and a front-end (if needed) called frontend as a service in your docker-compose:
version: '3.8'
services:
nginx:
image: nginx:1.19.4
depends_on:
- server
- frontend
volumes:
- ./default.conf:/etc/nginx/conf.d/default.conf
ports:
- '8080:80'
frontend:
build: ./frontend
backend:
build: ./backend
This is a bare minimum example to get started. Hope this will help future developers.