Docker: proxy_pass to another container - nginx: host not found in upstream

Question

(I know others have asked this question before, but I\'m not able to solve the problem using the solutions proposed in other posts, so i figured i would try to post my c

Answer 1

It's simple. Just change the old configuration:

upstream docker-web {
    server web:8000;
}

To this new one:

upstream docker-web {
    server web:80;
}

The reason is, between containers can't communicate with published port. It just can communicate with the target port. 8000:80 (8000 is published port and 80 is target port).

Let say you have 8000:443, you must create the configuration with "server web:443" inside Nginx listen to 443 port number. May this help.

Answer 2

Well you could achieve that by editing your /etc/hosts file and add the proper entry for your web host

1.1.1.1 web

Obviouslly you'll have to replace 1.1.1.1 with the web server's real ip address (a private one I suppose). Save the file and try again. Another workaround would be to replace in the config:

upstream docker-web {
    server web:8000;
}

with

upstream docker-web {
    server web-ip-address:8000;
}

If you'll go for the 2nd, don't forget to restart/reload nginx!

Answer 3

I figured out how to fix the problem. Got some help to fix the docker-compose.yml, so it looks like this:

docker-compose-yml:

version: "3"
services:
  web:
    image: user/repo:web
    deploy:
      resources:
        limits:
          cpus: "0.1"
          memory: 50M
      restart_policy:
        condition: on-failure
    ports:
      - "8000:80"
    networks:
        main:
            aliases:
                - web


  nginx:
    image: user/repo:nginx
    ports:
      - 80:80
    links:
      - web:web
    depends_on:
      - web
    networks:
        main:
            aliases:
                - nginx
networks:
  main:

After this the nginx container actually ran, but it was still not capable of connecting to the web-container. Found out I was able to use both curl web and curl web -p 8000 to get the page from web, from inside the nginx container. Then I changed the upstream in my nginx.conf from this

upstream docker-web {
    server web:8000;
}

to this:

upstream docker-web {
    server web;
}

Answer 4

Hello your problem is with the port when you linked web:web you need to specify the port in which the container runs the service for exemple

    ports:
  - "8000:80"

means inside the container i can access on port 80 but in the host machine i can acess via 8000. here's the doc about linking two services in docker-compose

so if you want to access web in proxy nginx don't use 8000 but use :

upstream docker-web {
server web:80;
  }

instead, this should work :)

or (those are both the same)

 upstream docker-web {
    server web;
      }