Docker nginx reverse proxy error - 502 bad gateway - connection refused - docker

Question

I'm having a problem with getting to work my NGINX reverse proxy on Docker.
When I access:
local.lab - NGINX responds with expected index.html page
127.0.0.1:2000 or 127.0.0.1:2001 or 127.0.0.1:2002 - service works and I get expected results
local.lab/a1 or local.lab/a2 or local.lab/a3 - I get "502 Bad Gateway" error.
Detailed error from nginx log:
2021/02/25 18:20:48 [error] 30#30: *4 connect() failed (111: Connection refused) while connecting to upstream, client: 172.19.0.1, server: local.lab, request: "GET /a2 HTTP/2.0", upstream: "http://127.0.0.1:2006/", host: "www.local.lab"
I tried to add network_mode: host to nginx service in docker compose without success.
I'm using docker compose:
version: '3.7'
services:
nginx:
container_name: lab-nginx
image: nginx:latest
restart: always
depends_on:
- http1
- http2
- http3
volumes:
- ./html:/usr/share/nginx/html/
- ./nginx.conf:/etc/nginx/nginx.conf
- ./error_log/error.log:/var/log/nginx/error.log
- ./cert:/var/log/nginx/cert/
ports:
- 80:80
- 443:443
http1:
container_name: lab-http1
image: httpd:latest
restart: always
# build:
# context: ./apache_service
ports:
- 2000:80
- 2005:443
volumes:
- ./apache/index1.html:/usr/local/apache2/htdocs/index.html
http2:
container_name: lab-http2
image: httpd:latest
restart: always
ports:
- 2001:80
- 2006:443
volumes:
- ./apache/index2.html:/usr/local/apache2/htdocs/index.html
http3:
container_name: lab-http3
image: httpd:latest
restart: always
ports:
- 2002:80
- 2007:443
volumes:
- ./apache/index3.html:/usr/local/apache2/htdocs/index.html
My nginx config:
worker_processes auto;
events { worker_connections 1024;}
error_log /var/log/nginx/error.log error;
http{
server {
listen 443 ssl http2;
server_name local.lab;
ssl_certificate /var/log/nginx/cert/local.lab.crt;
ssl_certificate_key /var/log/nginx/cert/local.lab.key;
ssl_protocols TLSv1.3;
location / {
root /usr/share/nginx/html;
index index.html;
}
location /a1 {
proxy_pass http://127.0.0.1:2000/;
proxy_set_header X-Forwarded-For $remote_addr;
}
location /a2 {
proxy_pass http://127.0.0.1:2001/;
proxy_set_header X-Forwarded-For $remote_addr;
}
location /a3 {
proxy_pass http://127.0.0.1:2002/;
proxy_set_header X-Forwarded-For $remote_addr;
}
}
}
How can I fix this?

Answer 1

The reverse proxy configuration in NGINX should reference the internal ports of your services, not the external ports they are mapped to in the docker-compose.yml. The services all have different names running in different containers so they can run on the same port (80 in this case) and use the service name, not the loopback address. You need to map them to different ports externally though because you can't have more than one service per port on your host.
For example:
location /a1 {
proxy_pass http://http1:80/;
proxy_set_header X-Forwarded-For $remote_addr;
}
location /a2 {
proxy_pass http://http2:80/;
proxy_set_header X-Forwarded-For $remote_addr;
}
location /a3 {
proxy_pass http://http3:80/;
proxy_set_header X-Forwarded-For $remote_addr;
}