Docker-compose: nginx does not work with django and gunicorn

Question

I've been trying to set up an environment in docker-compose where there are several containers:

• Django
• Nginx
• Postgres
• DbData
• Storage

I've used the following configuration:

 app:
  restart: always
  build: src
  expose:
    - "8000"
  links:
    - postgres:postgres
  volumes_from:
    - storage_files_1
  env_file: .env
  command: gunicorn barbell.wsgi:application \
            -b 0.0.0.0:8000 -w 4

nginx:
  restart: always
  build: nginx
  ports:
    - "80:80"
    - "443:443"
  volumes_from:
    - storage_files_1
  links:
    - app:app

postgres:
  restart: always
  image: postgres:latest
  volumes_from:
    - storage_data_1
  ports:
    - "5432:5432"

My nginx sites-enabled config file looked like this:

server {

    listen 80;
    server_name localhost;
    error_log /var/log/nginx/error.log;
    access_log /var/log/nginx/access.log;

    location /static {
        alias /static/;
        autoindex on;
    }

    location / {
         proxy_pass http://app:8000;
         proxy_set_header X-Forwarded-Host $server_name;
         proxy_set_header X-Real-IP $remote_addr;
         add_header P3P 'CP="ALL DSP COR PSAa PSDa OUR NOR ONL UNI COM NAV"';
    }
}

And it doesn't work - nginx always returns 502, but serves static files perfectly. I also tried the same setup with uwsgi, no luck. However, when I combine the Django with nginx and serve everything from the same container, everything works (again, both on uwsgi and gunicorn).

Any idea what am I missing?

Update

Here are the nginx logs:

*1 connect() failed (111: Connection refused) while connecting to upstream,
client: 172.17.42.1, server: 0.0.0.0, request: "GET / HTTP/1.1", upstream:   
"http://172.17.1.75:8000/", host: "localhost"

Answer 1

It turned out that Gunicorn was the culprit. Putting its configuration into a file resolved the issue.

gunicorn_config.py put in the same folder as manage.py:

bind = "0.0.0.0:8000"
loglevel = "INFO"
workers = "4"
reload = True

errorlog = "/var/log/gunicorn/error.log"
accesslog = "/var/log/gunicorn/access.log"

And some changes in docker-compose.yml:

app:
  restart: always
  build: src
  expose:
    - "8000"
  links:
    - postgres:postgres
  volumes_from:
    - storage_files_1
  env_file: .env
  command: gunicorn --config=gunicorn_config.py barbell.wsgi:application

Now it works as it should.