Django：在 Docker 上连接到 PostgreSQL 数据库时出现 OperationalError

Question

I have a problem with connecting Django with PostgreSQL installed in docker, when run Django using

python manage.py runserver

it returns the following error

OperationalError: could not translate host name "db" to address: Unknown host

settings.py:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'postgres',
        'USER': 'postgres',
        'PASSWORD': 'trytofindme',
        'HOST': 'db',
        'PORT': '5432',
    }
}

Dockerfile:

# pull official base image
FROM python:3.6.4-alpine

# set work directory
WORKDIR /usr/src/app

# set environment variables
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1

# install wkhtmltopdf dependencies
RUN wget https://s3.amazonaws.com/shopify-managemant-app/wkhtmltopdf-0.9.9-static-amd64.tar.bz2
RUN tar xvjf wkhtmltopdf-0.9.9-static-amd64.tar.bz2
RUN mv wkhtmltopdf-amd64 /usr/local/bin/wkhtmltopdf
RUN chmod +x /usr/local/bin/wkhtmltopdf

# install python dependencies
RUN pip install --upgrade pip
COPY ./requirements.txt /usr/src/app/requirements.txt
RUN apk --update add libxml2-dev libxslt-dev libffi-dev gcc musl-dev libgcc openssl-dev curl
RUN apk add jpeg-dev zlib-dev freetype-dev lcms2-dev openjpeg-dev tiff-dev tk-dev tcl-dev
RUN \
 apk add --no-cache postgresql-libs && \
 apk add --no-cache --virtual .build-deps gcc musl-dev postgresql-dev && \
 python3 -m pip install -r requirements.txt --no-cache-dir && \
 apk --purge del .build-deps

# copy project
COPY . /usr/src/app/

docker-compose:

version: '3.7'

services:
  db:
    image: postgres:13.0
    restart: always
    environment:
      POSTGRES_PASSWORD: trytofindme
    ports:
      - 15432:5432
  adminer:
    image: adminer
    restart: always
    ports:
      - 8020:8080

I can't find mistake in my code. Are there any variant to connect PostgreSQL and Django, not loosing the protection?

I used:

docker-compose up -d --build

And then:

docker-compose up

Docker container starts working and said, that db was ready to accept the connections. So I think, that problem is in my Django setup

Answer 1

The host has to be a hostname, so an address to your database. In your case, it should be set to either localhost or 127.0.0.1 . Django has no knowledge of the logical names of your Docker services.

Your docker-compose.yaml also specifies a different host port than the ones you put in your Django config (see docs ):

Either specify both ports (HOST:CONTAINER), or just the container port (an ephemeral host port is chosen).

You should either change the port in your Django config to 15432 , or better change the port mapping as follows

...

services:
  db:
    ...
    ports:
      - "5432:5432"
...

Using a standard port like 5432 is preferable because it makes it easier to identify host services/processes from the open ports on the host.