Linking django and mysql containers using docker-compose - mysql

Question

I've been following with the docker-compose tutorial here (linking django and postgres container). Although I was able to go through with the tutorial I'm however not able to proceed with repeating the same
using a mysql container.
The following are my dockerfile and docker-compose.yml
`
db:
image: mysql
web:
build: .
command: python manage.py runserver 0.0.0.0:8000
volumes:
- .:/code
ports:
- "8000:8000"
links:
- db:db
`
dockerfile
FROM python:2.7
RUN mkdir /code
WORKDIR /code
RUN pip install mysql-python
RUN pip install django
They both build fine when I do docker-compose up but it seems the db environment variables are not passed to the django container since when I run os.environ.keys() in one of my django views I can't see any of the expected DB_* environment variables.
So does mysql require a different setup or am I missing something.
Thank you.
[EDIT]
Docker compose version
docker-compose version: 1.3.0
CPython version: 2.7.9
OpenSSL version: OpenSSL 1.0.1e 11 Feb 2013
Docker version
Docker version 1.6.2, build 7c8fca2

Answer 1

In Django settings.py file make sure you have something like:
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.mysql',
'NAME': 'django1',
'USER': 'django',
'PASSWORD': 'password',
'HOST': 'db',
'PORT': 3306,
}
}
then in your docker-compose.yml file make sure you have something along the lines of:
db:
image: mysql
environment:
MYSQL_ROOT_PASSWORD: docker
MYSQL_DATABASE: docker
MYSQL_USER: docker
MYSQL_PASSWORD: docker
then as per the docker/django tutorial you are following run the following again to rebuild everything and things should start working
docker-compose run web django-admin.py startproject composeexample .
In response to a further question, the mysql root password variable is required by docker when creating new databases.
EDIT: added run to docker-compose above; see edit comment

Answer 2

you don't need to worry about environment variable. When linking containers together you just use the container alias defined by the link as if it was the hostname.
for instance if your docker-compose.yml file were:
db:
image: postgres
web:
build: .
command: python manage.py runserver 0.0.0.0:8000
volumes:
- .:/code
ports:
- "8000:8000"
links:
- db:mydb
In your django settings you would have to set the database host to mydb.

Answer 3

First you need to modify the settings file...
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql_psycopg2',
'NAME': 'postgres',
'USER': 'postgres',
'HOST': 'db',
'PORT': 5432,
} }
Then if you used the docker-compose command properly, the containers should be linked, and it should resolve the hostname db properly based on the links in the docker-compose.yml file.
Still, if you want to check the environment...
~/django-example: docker-compose run web env
Starting djangoexample_db_1...
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=66ff09ed8632
TERM=xterm
DJANGOEXAMPLE_DB_1_PORT=tcp://172.17.0.35:5432
DJANGOEXAMPLE_DB_1_PORT_5432_TCP=tcp://172.17.0.35:5432
DJANGOEXAMPLE_DB_1_PORT_5432_TCP_ADDR=172.17.0.35
DJANGOEXAMPLE_DB_1_PORT_5432_TCP_PORT=5432
DJANGOEXAMPLE_DB_1_PORT_5432_TCP_PROTO=tcp
DJANGOEXAMPLE_DB_1_NAME=/djangoexample_web_run_2/djangoexample_db_1
DJANGOEXAMPLE_DB_1_ENV_affinity:container==52c78c810792b0e7b9a231eab7ab7a3d50c95b76faf0abb8ec38a7d1ff0c7e5f
DJANGOEXAMPLE_DB_1_ENV_LANG=en_US.utf8
DJANGOEXAMPLE_DB_1_ENV_PG_MAJOR=9.4
DJANGOEXAMPLE_DB_1_ENV_PG_VERSION=9.4.4-1.pgdg70+1
DJANGOEXAMPLE_DB_1_ENV_PGDATA=/var/lib/postgresql/data
DB_PORT=tcp://172.17.0.35:5432
DB_PORT_5432_TCP=tcp://172.17.0.35:5432
DB_PORT_5432_TCP_ADDR=172.17.0.35
DB_PORT_5432_TCP_PORT=5432
DB_PORT_5432_TCP_PROTO=tcp
DB_NAME=/djangoexample_web_run_2/db
DB_ENV_affinity:container==52c78c810792b0e7b9a231eab7ab7a3d50c95b76faf0abb8ec38a7d1ff0c7e5f
DB_ENV_LANG=en_US.utf8
DB_ENV_PG_MAJOR=9.4
DB_ENV_PG_VERSION=9.4.4-1.pgdg70+1
DB_ENV_PGDATA=/var/lib/postgresql/data
DB_1_PORT=tcp://172.17.0.35:5432
DB_1_PORT_5432_TCP=tcp://172.17.0.35:5432
DB_1_PORT_5432_TCP_ADDR=172.17.0.35
DB_1_PORT_5432_TCP_PORT=5432
DB_1_PORT_5432_TCP_PROTO=tcp
DB_1_NAME=/djangoexample_web_run_2/db_1
DB_1_ENV_affinity:container==52c78c810792b0e7b9a231eab7ab7a3d50c95b76faf0abb8ec38a7d1ff0c7e5f
DB_1_ENV_LANG=en_US.utf8
DB_1_ENV_PG_MAJOR=9.4
DB_1_ENV_PG_VERSION=9.4.4-1.pgdg70+1
DB_1_ENV_PGDATA=/var/lib/postgresql/data
LANG=C.UTF-8
PYTHON_VERSION=2.7.10
PYTHON_PIP_VERSION=7.0.3
PYTHONUNBUFFERED=1
HOME=/root