CODEWITHSUNDEEP
djangopostgresqlamazon-web-servicesdocker-compose
Matheus Campello
Matheus Campello

Reputation: 447

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

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.

Upvotes: 39

Views: 63796

Answers (8)

adrian n
adrian n

Reputation: 51

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.

Upvotes: 0

Michelle Fernández
Michelle Fernández

Reputation: 408

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.

Upvotes: 1

Andreas
Andreas

Reputation: 9207

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

  1. Terminal: docker compose down --remove-orphans
  2. 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

Upvotes: 0

Lakshit Khanna
Lakshit Khanna

Reputation: 55

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

Upvotes: -2

tech
tech

Reputation: 189

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

Upvotes: 18

Mik Goldwyn
Mik Goldwyn

Reputation: 145

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

Upvotes: 12

Octatron
Octatron

Reputation: 19

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..

Upvotes: 1

Matheus Campello
Matheus Campello

Reputation: 447

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.

Upvotes: 4

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