docker nginx proxy nginx connect() failed (111: Connection refused) while connecting to upstream

Question

I'm trying to run a nginx container as the main entry point for all of my websites and web services. I managed to run a portainer as a container, and I'm able to reach it from the internet. Right now I'm trying to reach a static website hosted by another nginx container, but I fail doing so - when I go to the URL, I get

502 Bad Gateway

I've tried adding the upstream section to my main nginx's config, but nothing changed (after every config change, I reload my main nginx service inside the container).

On the other hand, adding upstream is something I'd like to avoid if it's possible because spawning multiple different applications would require adding an upstream for each application - and that's much more work than I'd expect.

Here is my main nginx's configuration file:

events {
    worker_connections 1024;
}
http {
    server {
        listen 80;

        location /portainer/ {
            proxy_pass http://portainer:9000/;
        }
        location /helicon/ {
            proxy_pass http://helicon:8001/;
        }
    }
}

Here is how I start my main nginx container:

docker run -p 80:80 --name nginx -v /var/nginx/conf:/etc/nginx:ro --net=internal-net -d nginx

Here is my static website's nginx configuration file:

events {
    worker_connections 1024;
}
http {
    server {
        listen  80;

    server_name helicon;
        root /var/www/html/helicon;

        error_log /var/log/nginx/localhost.error.log;
        access_log /var/log/nginx/localhost.access.log;
    }
}

Here is how the docker-compose file to create and start that container:

version: '3.5'
services:
    helicon:
        build: .
        image: helicon
        ports:
            - "127.0.0.1:8001:80"
        container_name: helicon
        networks:
            - internal-net
networks:
    internal-net:
        external: true

I'm using internal-net network to keep all apps in the same network instead of deprecated --link option for docker run

When I go to http://my.server.ip.address/helicon I get 502. Then I check logs with docker logs nginx and there is an information

2018/06/24 11:15:28 [error] 848#848: *466 connect() failed (111: Connection refused) while connecting to upstream, client: Y.Y.Y.Y, server: , request: "GET /helicon/ HTTP/1.1", upstream: "http://172.18.0.2:8001/", host: "X.X.X.X"

The helicon container indeed has an IP address of 172.18.0.2.

What am I missing? Maybe my approach should be completely different from using networks?

Kind regards,

Daniel

Answer 1

Solved. I was working on this for hours thinking it was a nginx config issue. I modified nginx.conf endlessly but couldn't fix it. I was getting 502 Bad Gateway and the error description was:

failed (111: Connection refused) while connecting to upstream

I was looking in the wrong place. It turns out that the http server in my index.js file was listening on the url 'localhost'.

httpServer.listen(PORT, 'localhost', async err => {

This works fine on your development machine, but when running inside a container it must be named the url of the container itself. My containers are networked, and in my case the container is named 'backend'

I changed the url from 'localhost' to 'backend' and everything works fine.

httpServer.listen(PORT, 'backend', async err => {