Postgres database, Error : NetworkError when attempting to fetch resource - docker

Question

I am trying to do a Docker image but I have some problems. Here is my docker-compose.yml :
version: '3.7'
services:
web:
container_name: web
build:
context: .
dockerfile: Dockerfile
command: python manage.py runserver 0.0.0.0:8000
volumes:
- .:/usr/src/web/
ports:
- 8000:8000
- 3000:3000
- 35729:35729
stdin_open: true
depends_on:
- db
db:
restart: always
environment:
- POSTGRES_USER=admin
- POSTGRES_PASS=pass
- POSTGRES_DB=mydb
- POSTGRES_PORT=5432
- POSTGRES_HOST=localhost
- POSTGRES_HOST_AUTH_METHOD=trust
container_name: db
image: postgres:12.0-alpine
volumes:
- postgres_data:/var/lib/postgresql/data/
volumes:
postgres_data:
And there my Dockerfile :
# pull official base image
FROM python:3.8.3-alpine
# set work directory
WORKDIR /usr/src/web
# set environment variables
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1
# install psycopg2 dependencies
RUN apk update \
&& apk add postgresql-dev gcc python3-dev musl-dev
# install nodejs
RUN apk add --update nodejs nodejs-npm
RUN apk add zlib-dev jpeg-dev gcc musl-dev
# copy project
COPY . .
RUN python -m pip install -U --force-reinstall pip
RUN python -m pip install Pillow
# install dependencies
RUN pip install --upgrade pip
RUN pip install -r requirements.txt
RUN pip install Pillow
# run entrypoint.sh
ENTRYPOINT ["sh", "./entrypoint.sh"]
Anf finally my entrypoint.sh :
#!/bin/sh
if [ "$DATABASE" = "postgres" ]
then
echo "Waiting for postgres..."
while ! nc -z $SQL_HOST $SQL_PORT; do
sleep 0.1
done
echo "PostgreSQL started"
fi
exec "$#"
When I do that :
docker-compose up -d --build
It works perfectly. Then I type that :
docker-compose exec web npm start --prefix ./front/
It looks ok but when I type in my browser http://localhost:3000/
I got that kind of messages : Error : NetworkError when attempting to fetch resource.
I thought the front is ok but I am not able to communicate with the back and so the database.
Could you help me please ?
Thank you very much !

Answer 1

As I can see in docker-compose.yml file you did not define the environment variables for Postgres in the web container. Please define the environment variables for the below :
DATABASE
SQL_HOST
SQL_PORT
Then bring down the docker and bring up the docker hopefully it will help you.