502 bad gateway with nginx and node inside docker

Question

I'm trying to run node and nginx each inside their own docker containers and proxy from nginx to node. I tried the configuration below without docker at first and it worked. However when using docker it's not working and gives Status Code:502 Bad Gateway when trying to connect to http://localhost/.

node server

var http = require('http');
http.createServer(function (req, res) {
    res.setHeader('content-type', 'text/html');
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Request-Headers', '*');
    res.setHeader('Access-Control-Request-Method', '*');
    res.setHeader('Access-Control-Allow-Methods', 'OPTIONS, GET');
    res.setHeader('Access-Control-Allow-Headers', '*');
    res.end('<html>Hey</html>');
}).listen(3001);

docker-compose.yml

version: '3'
services:
  app:
    build: ./servers
  nginx:
    build: ./nginx
    depends_on: 
      - app
    links:
      - app
    volumes:
      - ./nginx/conf:/etc/nginx/conf.d:ro
    ports: 
      - 80:80

nginx conf

server {
        listen 80;
        listen [::]:80;

        location / {
                proxy_pass http://app;
        }
}

app dockerfile

FROM node:alpine
RUN mkdir /app/
COPY ./server.js /app
EXPOSE 3001
WORKDIR /app
CMD node server

nginx dockerfile

FROM nginx:alpine
RUN rm /etc/nginx/conf.d/*

I'm not very familiar with Docker, so I might be asking stupid questions ;D Is there a mapping somewhere to port 3001 on which the Node server is running (I see it's being exposed, but I don't see where NGINX is told to use it). — robertklep
– robertklep, Commented Jun 8, 2017 at 16:44
@robertklep Yes, you are right, I fixed the error. . Do you want to answer the question ? — Ced
– Ced, Commented Jun 8, 2017 at 16:51
you solved it, so you get to answer it (as you already did :) — robertklep
– robertklep, Commented Jun 8, 2017 at 18:25

Ced · Accepted Answer · 2017-06-08 17:05:45Z

1

This now looks like a stupid question but I had the misconception that docker linked containers to whatever ports it opened without specifying the port. It turns out all the example I followed used port 80 on the other side. Anyway, enough with justifying myself, all I had to do was make the js server listen on port 80.

http.createServer(function (req, res) {
   ...
}).listen(80);

Alternatively I believe I could have used port 3001 in nginx conf

    location / {
            proxy_pass http://app:3001;
    }

edited Jun 8, 2017 at 17:05

answered Jun 8, 2017 at 16:56

Ced

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