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How to fix django.db.utils.OperationalError: could not translate host name "db" to address: Temporary failure in name resolution

Seen this question already asked but still no solution working for me.
My docker-compose:
version: '3.9'
services:
db:
image: postgres
volumes:
- ./data/db:/var/lib/postgresql/data
environment:
- POSTGRES_DB=postgres
- POSTGRES_USER=postgres
- POSTGREES_PASSWORD=password
web:
build: .
command: python manage.py runserver 0.0.0.0:8000
volumes:
- .:/books
ports:
- "8000:8000"
depends_on:
- db
my requirements.txt
Django>=3.2
psycopg2-binary>=2.8
my settings.py:
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER' : 'postgres',
'PASSWORD' : 'postgres',
'HOST' : 'db',
'PORT' : 5432,
}
}
my dockerfile:
FROM python:3
ENV PYTHONUNBUFFERED=1
WORKDIR /books
COPY requirements.txt /books/
RUN pip install -r requirements.txt
COPY . /books/
the error that is showing on my terminal
File "/usr/local/lib/python3.10/site-packages/psycopg2/__init__.py", line 122, in connect
web_1 | conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
web_1 | django.db.utils.OperationalError: could not translate host name "db" to address: Temporary failure in name resolution

django.db.utils.OperationalError: FATAL: password authentication failed for user "postgres" - django

I am trying docker-compose an app with django and postgres using docker-compose but I get an error with the "NAME"
Here is my settings.py
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'PASSWORD': 'postgres',
'HOST': 'db',
'PORT': 5432,
}
}
Here is my docker-compose
version: "3.9"
services:
db:
restart: always
image: postgres:latest
ports:
- "5432:5432"
volumes:
- ./data/db:/var/lib/postgresql/data
environment:
- POSTGRES_DB=postgres
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=postgres
web:
restart: always
build: ./backend
command: python manage.py runserver 0.0.0.0:8000
volumes:
- .:/usr/src/app
ports:
- "8000:8000"
depends_on:
- db
django.db.utils.OperationalError: FATAL: password authentication
failed for user "postgres"
Thanks for your help

Lots of things were wrong in my code.
After 6 hours of debugging.
First I changed all my docker-compose.yml to
version: "3.9"
services:
db:
image: postgres
volumes:
- ./data/db:/var/lib/postgresql/data
web:
build: ./backend
command: python manage.py runserver 0.0.0.0:8000
volumes:
- .:/usr/src/app
ports:
- "8000:8000"
depends_on:
- db
In my settings.py I did:
import environ
import os
env = environ.Env(
# set casting, default value
DEBUG=(bool, False)
)
# Set the project base directory
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
# Take environment variables from .env file
environ.Env.read_env(os.path.join(BASE_DIR, '.env'))
# False if not in os.environ because of casting above
DEBUG = env('DEBUG')
# Raises Django's ImproperlyConfigured
# exception if SECRET_KEY not in os.environ
SECRET_KEY = env('SECRET_KEY')
# Parse database connection url strings
# like psql://user:pass#127.0.0.1:8458/db
DATABASES = {
# read os.environ['DATABASE_URL'] and raises
# ImproperlyConfigured exception if not found
#
# The db() method is an alias for db_url().
'default': env.db(),
}
I then created the .env
DEBUG=on
SECRET_KEY=xxx
DATABASE_URL=psql://postgres:123#db:5432/postgres
I then entered into docker using
docker ps -a
docker exec -it <container_id> bash
psql postgres postgres
\password postgres
123
123
I then migrated my database
docker-compose exec web python manage.py makemigrations
docker-compose exec web python manage.py migrate

django OperationalError when trying to migrate with docker

django.db.utils.OperationalError: could not translate host name "db" to address: Name or service not known
That is the error I get when running docker-compose exec web python manage.py migrate
my docker-compose.yml contains:
version: '3.8'
services:
web:
build: .
command: python /code/manage.py runserver 0.0.0.0:8000
volumes:
- .:/code
ports:
- 8000:8000
depends_on:
- db
db:
image: postgres:11
This Is what I put for DATABASE in settings.py:
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'PASSWORD': 'postgres',
'HOST': 'db',
'PORT': 5432
}
}
I have tried running docker-compose up -d --build and then docker-compose exec web python manage.py migrate
But that doesn't work.

You will need to add an environment for your db service:
services:
# ...
db:
# ...
environment:
POSTGRES_PASSWORD: postgres
as POSTGRES_PASSWORD is the only non-optional env variable needed to run the image as stated in the docs.

Can't connect to MySQL while building docker-compose image

I have a configuration of docker-compose, and on building database step, django management throws an error:
django.db.utils.OperationalError: (2002, "Can't connect to MySQL server on '127.0.0.1' (115)")
I think - the docker refusing connections.
Configuration by socket similar not working (Says error connection by socket)
Docker Compose file
version: '3'
services:
db:
image: mariadb:5.5
restart: always
environment:
MYSQL_ROOT_PASSWORD: "root"
MYSQL_DATABASE: "bh"
MYSQL_USER: "root"
MYSQL_PASSWORD: "root"
ports:
- "3302:3306"
behealthy_dev:
build: .
container_name: behealthy_dev
expose:
- "86"
command: python manage.py runserver 0.0.0.0:80
volumes:
- /behealthy_dev/
ports:
- "86:86"
depends_on:
- db
Dockerfile
FROM python:3.6
ENV PYTHONUNBUFFERED 1
RUN mkdir /behealthy_dev
WORKDIR /behealthy_dev
ADD requirements.txt /behealthy_dev/
RUN pip install -r requirements.txt
ADD . /behealthy_dev/
RUN python manage.py makemigrations
RUN python manage.py migrate
RUN python manage.py collectstatic --noinput
Database settings (settings)
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.mysql',
'NAME': 'bh',
'HOST': '127.0.0.1',
'PORT': '3306',
'USER': 'root',
'PASSWORD': 'root',
'OPTIONS': {
'sql_mode': 'traditional',
'init_command': 'SET innodb_strict_mode=1',
'charset': 'utf8mb4',
},
},
}
Have any solutions? I tried to resolve from other stack answer but it's not working for me.

in your service behealthy_dev change the MySQL host from
'HOST': '127.0.0.1'
to
'HOST': 'db',
Edit:
Change also the MYSQL_ROOT_PASSWORD: "root" to:
`MYSQL_ROOT_PASSWORD: "rootpassword"`
and your Database settings to:
'PASSWORD': 'rootpassword',

Wrong configuration for database in seetings.py or docker

I'm learning how to work with Compose + Django using this manual https://docs.docker.com/compose/django/
Here are my configuration files
docker-compose.yml
version: '3'
services:
db:
image: postgres
web:
build: .
command: python3 manage.py runserver 0.0.0.0:8000
volumes:
- .:/code
ports:
- "8000:8000"
depends_on:
- db
setting.py
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'HOST': 'db',
'PORT': 5432,
}
}
When I run using docker-compose up everything is fine.
But when I run using python manage.py runserver I got this error
psycopg2.OperationalError: could not translate host name "db" to address: Name or service not known
Guess, I have wrong cofiguration

You forgot set hostname in db service.
version: '3'
services:
db:
image: postgres
hostname: db
web:
build: .
command: python3 manage.py runserver 0.0.0.0:8000
volumes:
- .:/code
ports:
- "8000:8000"
depends_on:
- db
Tip: Don't use runserver when you deploy production server. Check this doc
The solution is described in comments
Edit)
separate settings example. Make your original settings.py to base.py in settings folder.
<your_app>/settings/local.py
from .base import *
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'HOST': 'localhost',
'PORT': 5432,
}
}
<your_app>/settings/deploy.py
from .base import *
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'HOST': 'db',
'PORT': 5432,
}
}
So finally, your settings folder contains three python file. base.py, local.py, deploy.py
And when you run server with local settings, python manage.py runserver --settings <your_app>.settings.local.

This is a common problem in docker/django setup , postgres container is initialized but the engine is not ready yet.
You must wait for the postgresql server to start before running the web container.
You can do this in several ways , have a look at dockerize
dockerize -timeout=20s -wait ${POSTGRES_PORT}

I guess you trying to run manage.py runserver on host machine. Error means, that you have no access to host 'db' from it (try ping db in console). There are several causes of this:
Your docker container db is down. Try run docker-compose up -d db
You are using Windows as host system. In Windows there is no access to containers from host, you must install postgres locally.
You have networking problems. Try ping 127.0.0.11 (it's docker's DNS server)
P.S. Do you really want local Django use Postgres in container?