Question

Unable to connect Nginx and backend container in my droplet

hello. I am running my web app constituted of

  • nginx (installed directly in the droplet)
  • django container (backend)
  • Next.js container (frontend0. I deploy all in the droplet I bought a domain name and pointed it to my IP server adress.

My app is running well locally, After deployement, I am getting the famous 502 bad gateway. i have the following files /etc/nginx/sites-available/web.conf


###########################################  UPSTREAMS

#upstream django_upstream {
#  server django:8000;
#}


#upstream nextjs_upstream {
#  server frontend:3000;
#}

############################################  SERVER

server {
    listen 80;
    server_name domain.com www.domain.com.ca;
    #server_tokens off;

    location / {
       try_files $uri @proxy_frontend;
    }

    location @proxy_frontend {
        proxy_set_header X-Forwarded-Proto https;
        proxy_set_header X-Url-Scheme $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_pass http://localhost:3000;
        #proxy_pass   http://nextjs_upstream; <--- (tried this with upstrea. but not worked)
    }

    
    #----------------------      Backend      ------------------------------


    location /backend/api {
        try_files $uri @proxy_api;
    }

    location /backend/api/docs {
        try_files $uri @proxy_api;
    }

    location /admin {
        try_files $uri @proxy_api;
    }

    location @proxy_api {
        proxy_set_header X-Forwarded-Proto https;
        proxy_set_header X-Url-Scheme $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_pass http://localhost:8000;
        # proxy_pass   http://django_upstream; <--- (tried this with upstrea. but not worked)
    }

    location /django_static/ {
        alias /app/backend/staticfiles/;
    }

    location /django_media/ {
        alias /app/backend/mediafiles/;
    }


}

and my docker-compose file is

version: '3.9'

services:
  db:
    build:
      context: .
      dockerfile: ./docker/database/Dockerfile
    container_name: c-db
    restart: always
    volumes:
      - db:/var/lib/postgresql/data
    environment:
      - POSTGRES_DB=${DB_NAME}
      - POSTGRES_USER=${DB_USER}
      - POSTGRES_PASSWORD=${DB_PASS}

  django:
    hostname: django
    restart: always
    image: i-api-prod:django-prod
    container_name: c-api
    build:
      context: .
      dockerfile: ./docker/backend/Dockerfile
    volumes:
      - staticfiles:/app/backend/staticfiles
      - mediafiles:/app/backend/mediafiles
    environment:
      - DB_HOST=db
      - DB_NAME=${DB_NAME}
      - DB_USER=${DB_USER}
      - DB_PASS=${DB_PASS}
      - SECRET_KEY=${DJANGO_SECRET_KEY}
      - ALLOWED_HOSTS=${DJANGO_ALLOWED_HOSTS}
    expose:
      - 8000
    depends_on:
      - db
    # networks:
    #   - django-network

  frontend:
    hostname: frontend
    build:
      context: .
      dockerfile: ./docker/frontend/Dockerfile
    container_name: c-frontend
    expose:
      - 3000

    # volumes:
    #   - frontend_static_assets:/app/frontend/static_assets
    depends_on:
      - django

volumes:
  db:
  staticfiles:
  mediafiles:

The .env file for my project is


# Database variables

DB_NAME=dbname
DB_USER=rootuser
DB_PASS=changeme



DJANGO_SECRET_KEY=secretkey_for_production_environment


DJANGO_ALLOWED_HOSTS=localhost 0.0.0.0 


# Frontend variables

API_BASE_URL="http:0.0.0.0/backend"

When I check nginx status is active(running).

  • When I tried to a request in the broweser and check the logs, I obtained the following error.
2022/12/31 13:44:51 [error] 42558#42558: *62 connect() failed (111: Unknown error) while connecting to upstream, client: 31.2.136.184, server: domain.com, request: "GET /2.FKbxrpmVH1CttsoTtQEudY?O8A=bMnAfQJ7939h5tlyVuH_Uog&uS=ulh.AJJYMMaSJctgUQWEwiIZ.D&RPFsTVxAu=XkD HTTP/1.1", upstream: "http://localhost:3000/2.FKbxrpmVH1CttsoTtQEudY?O8A=bMnAfQJ7939h5tlyVuH_Uog&uS=ulh.AJJYMMaSJctgUQWEwiIZ.D&RPFsTVxAu=XkD", host: "www.ws.k12.ny.us"

and the understand that the problem is not nginx, but the connection to my backend and frontend. But I don’t know how to fix it.


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Bobby Iliev
Site Moderator
Site Moderator badge
January 3, 2023

Hi there,

Indeed the Nginx configuration looks good. The error indicates that the Docker container that is supposed to be running on 3000 is not reachable.

If you check the container status with docker ps -a is the container up and running?

Also if you check the logs of that container do you see any errors in there?

Best,

Bobby