Using Nginx reverse proxy with Docker - docker

Question

I am trying to develop a distributed Angular app deployed on Nginx that should connect to a backend service.
docker-compose.yml:
version: '3'
services:
backend_service_1:
build:
context: ./app
dockerfile: Dockerfile
ports:
- "3001:5000"
networks:
- my-network
frontend:
build:
context: ./frontend
dockerfile: Dockerfile.3
ports:
- "3000:80"
networks:
- my-network
links:
- backend_service_1
networks:
my-network:
nginx.conf:
upstream backend {
server backend_service_1:3001;
}
server {
listen 80;
server_name localhost;
location / {
root /usr/share/nginx/html/ki-poc;
index index.html index.htm;
try_files $uri $uri/ /index.html =404;
}
location /backend {
proxy_pass http://backend/;
proxy_redirect off;
proxy_set_header Host $host;
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;
}
}
I can access the app on localhost:3000. I can also get a response from the backend service on localhost:3001 using the browser. However, when I try to get a response from the backend service using the proxy on localhost:3000/backend I receive the following error message:
[error] 5#5: *4 connect() failed (111: Connection refused) while connecting to upstream, client: 172.20.0.1, server: localhost, request: "GET /backend HTTP/1.1", upstream: "http://172.20.0.2:3001/", host: "localhost:3000"
Can you tell my, why the request to the linked backend container is getting refused?

Answer 1

You shoul use the port of the container in the nignx config, not the one of the host.
upstream backend {
server backend_service_1:5000;
}