Docker-compose with django could not translate host name "db" to address: Name or service not known

Question

I have currently a system built with docker-compose, it creates a Django application.

Up until now I've used a database inside a container (postgresql) in my testing build. Now I've changed the database from this container to an RDS instance in AWS.

Using Pg_dump I have recreated the database inside RDS and changed the settings.py, everything was supposedly normal. I have accessed the data from the database inside my webapp without any problems.

Everything was ok until I had to make a migration. Without the database container the Django container gives me this message:

django.db.utils.OperationalError: could not translate host name "db" to address: Name or service not known

My Docker-compose.yml file before the changes:

 version: '2'

    services:
      db:
        image: postgres:9.5
        restart: always
        environment:
          POSTGRES_USER: testing
          POSTGRES_PASSWORD: tests
          POSTGRES_DB: test
        volumes:
          - /dbdata:/var/lib/postgresql/data
      django:
        build: ./django
        command: gunicorn contactto.wsgi:application -b 0.0.0.0:8000
        restart: always
        volumes:
          - ./django:/usr/src/app
          - ./django/static:/usr/src/app/contactto/static
        ports:
          - "8000:8000"
        depends_on:
          - db

Now after the changes:

    version: '2'

    services:
      django:
        build: ./django
        command: gunicorn contactto.wsgi:application -b 0.0.0.0:8000
        restart: always
        volumes:
          - ./django:/usr/src/app
          - ./django/static:/usr/src/app/contactto/static
        ports:
          - "8000:8000"

And the DATABASES from settings.py . Before:

DATABASES = {
        'default': {
            'ENGINE': 'tenant_schemas.postgresql_backend',
            'NAME': 'testing',
            'USER': 'test',
            'PASSWORD': 'test',
            'HOST': 'db',
            'PORT': '5432',
        }
    }

After:

DATABASES = {
        'default': {
            'ENGINE': 'tenant_schemas.postgresql_backend',
            'NAME': 'testing',
            'USER': 'test',
            'PASSWORD': 'test',
            'HOST': 'xxx.rds.amazonaws.com',
            'PORT': '5432',
        }
    }

The weird thing is, I can use the aws database inside my app... I can create users and do things inside the database and the changes appear. Now in the CLI I can't even use manage.py shell without the message.

I am completely lost.

The answer can be found at this stackoverflow.com/a/61393097/10526787 — curtly critchlow
– curtly critchlow, Commented Jul 10, 2020 at 12:04

tech · Accepted Answer · 2020-05-23 12:14:07Z

19

Add network, link and depends_on configuration in docker compose file.

example:

  services:
      db:
          build: .
          container_name: db
          networks:
              - djangonetwork
      web:
          build: .
          depends_on:
             - db
          links:
             - db:db
          networks:
             - djangonetwork

  networks:
      djangonetwork:
          driver: bridge

answered May 23, 2020 at 12:14

tech

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2 Comments

Neil Gaetano Lindberg Over a year ago

This greatly helped me get past the docs.docker Quickstart, which is sans networks. Two things I tripped up on with this is the networks being at the same level as services and adding the networks to both the web and db configurations.

ztindall Over a year ago

This got me past a problem with my compose file. Namely I did not have the networks field for my web defined.

Mostafa Barmshory · Accepted Answer · 2020-04-11 09:40:22Z

12

To the others experiencing this.

The following command (which removes all unused containers, networks, images, and optionally, volumes) solve my problem:

docker system prune

See docker document for more information

edited Apr 11, 2020 at 9:40

Mostafa Barmshory

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answered Apr 10, 2020 at 14:33

Mik Goldwyn

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3 Comments

snakecharmerb Over a year ago

It would be much better if this answer explained why taking this action fixes the problem.

sajid Over a year ago

Why does this work? Is it a magic spell?

geekt Over a year ago

Usually such an error appears because docker volumes overreach the limit of how much size can be stored. If the data generated by all volumes reach a certain threshold (disk space), containers stop to function properly (especially when a --build operation is performed). docker system prune is a way of freeing memory, thus allowing to container to allocate memory and have enough space to function properly. This is why this command works like charm.

Matheus Campello · Accepted Answer · 2017-01-10 16:59:20Z

4

Answering my question, this was a stupid one...

My manage.py was selecting only the base.py settings file, and was not taking into account the staging.py settings file. So it was breaking in the CLI and was not breaking inside the app.

answered Jan 10, 2017 at 16:59

Matheus Campello

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4 Comments

John Mee Over a year ago

Does that mean you didn't have the settings file configured correctly?

Yash Marmat Over a year ago

Can someone elaborate how he fixed that issue? I'm also getting this error it's being two days and I didn't find a solution :(

Rob Over a year ago

I had this same issue while trying to run tests in Github Actions. The key insight is that your django app is starting up and attempting to connect to postgres. Somewhere in your settings, or in inherited settings at the time of run, the database name / port config is incorrect. If you think you know where you're setting it, and you change it, and still see 'db' then it is being overridden somewhere or you aren't actually working with the branch you think you are.

Hamedio Over a year ago

@JohnMee No as he said his manage.py was pointing toward wrong settings file.See in application development a good practice is making several settings file for diffrent environments which will make running program smother , safer and faster in each environment.

Octatron · Accepted Answer · 2018-08-07 02:04:21Z

1

In the "django" part of your docker-compose.yml under "depends_on" section try adding links: - db:db after it, or even replace the depends_on: db with that.

I'll bet if you typed in docker logs (container name) you'd see it's obviously having trouble working out where "db" points to.

I think they're looking to end support for links in docker-compose in new iterations at least I read that somewhere..

answered Aug 7, 2018 at 2:04

Octatron

191 bronze badge

Comments

Michelle Fernández · Accepted Answer · 2023-06-22 18:39:57Z

1

FWIW, for anyone using Podman, this issue could be due to the containers not being able to find each other within the network. This post helped me solve the problem https://github.com/containers/podman/issues/9292.

Essentially, you also need to make sure that the network's dns_enable is set to true.

answered Jun 22, 2023 at 18:39

Michelle Fernández

4183 silver badges9 bronze badges

Comments

Andreas · Accepted Answer · 2023-02-28 23:20:02Z

0

If you use docker (compose), you can try:

Terminal: docker compose down --remove-orphans
Terminal: docker compose up -d

The problem seems to occure because of stale containers/networks which are interfering with the DNS resolution. By using docker system prune or a simple down and up you remove/restart those containers. By using --remove-orphans you also take care of containers not started by the docker-compose.yml

edited Feb 28, 2023 at 23:20

answered Feb 28, 2023 at 23:13

Andreas

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Comments

adrian n · Accepted Answer · 2024-12-20 09:07:06Z

0

For me the problem was that I was running makemigrations && migrate on build Dockerfile, so database wasn't running at that stage. I had to run migrations on CMD instead.

answered Dec 20, 2024 at 9:07

adrian n

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Comments

Ceres · Accepted Answer · 2021-03-14 10:57:21Z

-2

click on this link to get your answer or add command: bash -c "python manage.py migrate && python manage.py runserver 0.0.0.0:8000" in docker-compose.yaml.I hope this will work for you. It worked for me

edited Mar 14, 2021 at 10:57

Ceres

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answered Mar 14, 2021 at 2:23

Lakshit Khanna

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1 Comment

sajid Over a year ago

Why did it work for you and why should it work for them?

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