[Django]-How to connect postgis to django in docker

NOTE: There is an official image for postgis now https://hub.docker.com/r/postgis/postgis. Use that instead. Also in example below I am using alpine which is not recommended as python base due to issues with wheels (read more https://pythonspeed.com/articles/alpine-docker-python/)

Problem here that you are not using correct postgis image

version: '3'

services:
  web:
    build: .
    command: python3 manage.py runserver 0.0.0.0:8000
    volumes:
      - .:/code
    ports:
      - "8000:8000"
    depends_on:
      - db
  db:
    image: mdillon/postgis:10 # <- here
    environment:
      - POSTGRES_HOST=db  # default postgres
      - POSTGRES_PASSWORD=password  # default postgres
      # all env vars bellow are redundant because they are same as default values
      # - POSTGRES_PORT=5432
      # - POSTGRES_NAME=postgres
      # - POSTGRES_USER=postgres

Here is my alpine based config for working with postgis

NOTE: all my django code is stored in ./backend folder and I use Pipenv, also
this project is using https://github.com/joke2k/django-environ to set DATABASES via DATABASE_URL in my settings

DATABASES = {
    'default': env.db(default='postgis://postgres:postgres@postgres:5432/postgres')
}

docker-compose.yml

version: "3.7"


services:

    postgres:
        image: mdillon/postgis:10-alpine
        volumes:
            - ./docker/postgres/:/docker-entrypoint-initdb.d/
            - postgres_data:/var/lib/postgresql/data

    backend:
        build:
            context: .
            dockerfile: docker/backend/Dockerfile
        ports:
            - "8000:8000"
        depends_on:
            - postgres
        volumes:
            - ./backend:/project/backend


volumes:
    postgres_data:

docker/backend/Dockerfile

FROM python:3.6-alpine3.8

# postgresql-client is required by psql
# postgresql-dev musl-dev gcc are required by psycopg
# NOTE: there is py3-psycopg2
# libxml2-dev libxslt-dev are required by lxml
# gdal-dev geos-dev proj4-dev are required by geodjango
# libcrypto1.1 is required by gdal
# NOTE: we actually need gdal-dev not gdal
# linux-headers is required by uwsgi
# gettext-dev is required by ./manage.py makemessages

# TODO: optimize installation by using --virtual
RUN apk update && apk upgrade \
    && apk add postgresql-client \
        postgresql-dev \
        musl-dev \
        gcc \
        libxml2-dev \
        libxslt-dev \
        linux-headers \
        gettext-dev \
    && apk add --repository http://dl-cdn.alpinelinux.org/alpine/edge/main \
        libcrypto1.1 \
    && apk add --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing \
        gdal-dev \
        geos-dev \
        proj4-dev \
    && pip install pipenv

ENV PYTHONUNBUFFERED=1 \
    PYTHONIOENCODING=UTF-8

COPY docker/backend/docker-entrypoint.sh /
ENTRYPOINT ["/docker-entrypoint.sh"]

WORKDIR /project/backend

COPY backend/Pipfile backend/Pipfile.lock /project/backend/

RUN pipenv install --system --ignore-pipfile --dev

docker/backend/docker-entrypoint.sh

#!/bin/sh
# NOTE: if there is no bash can cause
# standard_init_linux.go:190: exec user process caused "no such file or directory"

# https://docs.docker.com/compose/startup-order/
set -euo pipefail

WAIT_FOR_POSTGRES=${WAIT_FOR_POSTGRES:-true}

if [[ "$WAIT_FOR_POSTGRES" = true ]]; then
    DATABASE_URL=${DATABASE_URL:-postgres://postgres:postgres@postgres:5432/postgres}

    # convert to connection string
    # https://www.postgresql.org/docs/current/static/libpq-connect.html#LIBPQ-CONNSTRING
    POSTGRES_URL=${DATABASE_URL%%\?*}
    # https://www.gnu.org/software/bash/manual/bash.html#Shell-Parameter-Expansion
    POSTGRES_URL=${POSTGRES_URL/#postgis:/postgres:}

    # let postgres and other services (e.g. elasticsearch) to warm up...
    # https://www.caktusgroup.com/blog/2017/03/14/production-ready-dockerfile-your-python-django-app/
    until psql $POSTGRES_URL -c '\q'; do
        >&2 echo "Postgres is not available - sleeping"
        sleep 1
    done
    # >&2 echo "Postgres is up - executing command"
fi

if [[ $# -ge 1 ]]; then
    exec "$@"
else
    echo "Applying migrations"
    python manage.py migrate --noinput -v 0
    echo "Generate translations"
    python manage.py compilemessages --locale ru -v 0
    echo "Starting server"
    exec python manage.py runserver 0.0.0.0:8000
fi