Ngnix Django 502 网关坏

Question

I deployed a django app using CI/CD from gitlab. The app is wrapped in a docker container and uses Nginx server. The deployment is successful from git but I get the error when I visit the IP.

502 Bad Gateway
nginx/1.17.4

I checked the log of the app's container and it outputs

no destination
no destination
no destination
no destination
no destination
no destination
no destination

Also, that of the Nginx container outputs

2020/06/06 16:49:29 [error] 6#6: *754 connect() failed (111: Connection refused) while connecting to upstream, client: 196.251.20.105, server: , request: "GET /favicon.ico HTTP/1.1", upstream: "http://172.18.0.3:8000/favicon.ico", host: "18.189.11.120", referrer: "http://18.189.11.120/"
196.251.20.105 - - [06/Jun/2020:16:49:29 +0000] "GET /favicon.ico HTTP/1.1" 502 559 "http://18.189.11.120/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36" "-"

For some additional context, I will post the content of some of my files

Dockerfile

FROM python:3.6-slim

# create the appropriate directories

ENV APP_HOME=/web
RUN mkdir $APP_HOME
RUN mkdir $APP_HOME/static
RUN mkdir $APP_HOME/mediafiles
WORKDIR $APP_HOME



ENV PYTHONUNBUFFERED=1

# Add unstable repo to allow us to access latest GDAL builds
# Existing binutils causes a dependency conflict, correct version will be installed when GDAL gets intalled
RUN echo deb http://deb.debian.org/debian testing main contrib non-free >> /etc/apt/sources.list && \
    apt-get update && \
    apt-get remove -y binutils && \
    apt-get autoremove -y

# Install GDAL dependencies
RUN apt-get install -y libgdal-dev g++ --no-install-recommends && \
    pip install pipenv && \
    pip install whitenoise && \
    pip install gunicorn && \
    apt-get clean -y

# Update C env vars so compiler can find gdal
ENV CPLUS_INCLUDE_PATH=/usr/include/gdal
ENV C_INCLUDE_PATH=/usr/include/gdal

ENV LC_ALL="C.UTF-8"
ENV LC_CTYPE="C.UTF-8"

# -- Adding Pipfiles
# COPY Pipfile Pipfile
# COPY Pipfile.lock Pipfile.lock
# COPY package.json package.json

# -- Install dependencies:
RUN pip install --upgrade pip
COPY ./requirements.txt /web/requirements.txt
RUN pip install -r requirements.txt

RUN apt-get update -yq \
    && apt-get install curl gnupg -yq \
    && apt-get install -y netcat \
    && curl -sL https://deb.nodesource.com/setup_8.x | bash \
    && apt-get install nodejs -yq

# copy entrypoint.sh
COPY ./entrypoint.prod.sh /web/entrypoint.prod.sh

# copy project
COPY . /web/

# run entrypoint.sh
ENTRYPOINT ["/web/entrypoint.prod.sh"]

entrypoint.prod.sh

#!/bin/sh

if [ "$DATABASE" = "postgres" ]
then
    echo "Waiting for postgres..."

    while ! nc -z $SQL_HOST $SQL_PORT; do
      sleep 0.1
    done

    echo "PostgreSQL started"
fi

exec "$@"

docker-compose.yml

version: '3.7'

services:
  web:
    image: "${WEB_IMAGE}"
    command: gunicorn web.wsgi:application --bind 0.0.0.0:8000
    volumes:
      - static_volume:/web/staticfiles
      - media_volume:/web/mediafiles
    ports:
      - 8000:8000
    env_file: .env
    depends_on:
      - db
  nginx:
    image: "${NGINX_IMAGE}"
    volumes:
      - static_volume:/web/staticfiles
      - media_volume:/web/mediafiles
    ports:
      - 80:80
    depends_on:
      - web
  db:
    image: postgres:12.0-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data/
    env_file: .env

volumes:
  postgres_data:
  static_volume:
  media_volume:

Nginx Dockerfile

FROM nginx:1.17.4-alpine

RUN rm /etc/nginx/conf.d/default.conf
COPY nginx.conf /etc/nginx/conf.d

nginx.conf

upstream web {
    server web:8000;
}

server {

    listen 80;

    location / {
        proxy_pass http://web;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
    }

    location /static/ {
        alias /web/static/;
    }

    location /mediafiles/ {
        alias /web/mediafiles/;
    }

}

Answer 1

you should make link from web to nginx in docker-compose.yml,

nginx:
  ...
  links:
     - "web"

Your nginx don`t see upstream web . more info: https://docs.docker.com/compose/compose-file/#links

Answer 2

This should not be your case, but I had a similar problem and the error was due to the connection of my application to an external database.

One way to try to find the problem is to access the web container and run curl localhost:8000 to see if it works locally.

Another attempt you can make is to use networks, something like this:

version: '3.7'

services:
  web:
    image: "${WEB_IMAGE}"
    command: gunicorn web.wsgi:application --bind 0.0.0.0:8000
    volumes:
      - static_volume:/web/staticfiles
      - media_volume:/web/mediafiles
    ports:
      - 8000:8000
    env_file: .env
    depends_on:
      - db
    networks:
      - nginx-network
      - db-network
  nginx:
    image: "${NGINX_IMAGE}"
    volumes:
      - static_volume:/web/staticfiles
      - media_volume:/web/mediafiles
    ports:
      - 80:80
    depends_on:
      - web
    networks:
      - nginx-network
  db:
    image: postgres:12.0-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data/
    env_file: .env
    networks:
      - db-network

volumes:
  postgres_data:
  static_volume:
  media_volume:

networks:
  nginx-network:
    driver: bridge
  db-network:
    driver: bridge