This document discusses dockerizing a Django web application. It begins by outlining problems with differing environments and proposes containerizing the application using Docker to help standardize environments. It then provides steps to containerize a simple Django app, add database and admin services, configure environment variables, add static file serving and logging. The goal is to make development and production environments more similar to improve productivity.

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Docker and Django
Hendrik Frentrup
hendrik@systemati.co
31 January 2019
Auckland, NZ

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Ways to get in touch
hendrik@systemati.co
@HendrikFrentrup
linkedin.com/in/frentrup/
github.com/hendrikfrentrup
medium.com/@hendrik.frentrup

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Links
•GitHub repo for the code
•github.com/hendrikfrentrup/docker-django
•Walkthrough:
•medium.com/devopslinks/tech-edition-how-to-dockerize-a-django-web-
app-elegantly-924c0b83575d
•https://medium.com/@hendrik.frentrup/tech-edition-django-dockerization-
with-bells-and-whistles-and-a-tad-bit-of-cleverness-2b5d1b57e289
•Further reading:
•medium.com/panaseer-labs-engineering-data-science/how-devops-
helped-us-solve-our-big-data-development-problem-263474dfeedb
•Contact details:
•Email: hendrik@systemati.co
•Twitter: @hendrikfrentrup
•LinkedIn: linkedin.com/in/frentrup/

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The Problem
• Moving code from development environments to staging or
production can break things
• The state of environments drifts and is hard to manage
• For lack of access, developers have no insight into the specifics of
production environments

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From here
Application
Database
Local machine

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To here
Docker
web
gunicorn
server
db
postgres
Local machine
db-admin
pgadmin
server
nginx
nginx
server
python
manage.py
runserver
*.conf
+ static/
pg-data/

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• Move a locally running app into a container
• Setup database, admin and nginx services
• Run migrations
• Logging
• Infrastructure-as-code
• Bring development and production
environments close together
• Increased productivity
Outline

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Simple app running locally
python manage.py runserver
db.sqlite3
Local machine

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10 commands to set up
> git init
> git checkout -b develop
> virtualenv env
> source env/bin/activate
> pip install Django>=2.1
> echo 'Django>=2.1' >> requirements.txt
> django-admin startproject my-site
> git add * && git commit -m "..."
> python mysite/manage.py runserver

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App running in container
Docker
web
python manage.py runserver
db.sqlite3
Local machine

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App inside Docker
> touch Dockerfile
> docker build -t django-docker:0.0.1 .
> docker run -p 8001:8001 docker-django:0.0.1
______Dockerfile____________________________________________________________
FROM python:3.6.7-alpine
ENV PYTHONUNBUFFERED 1
RUN mkdir /code
WORKDIR /code
ADD ./ /code/
RUN pip install -r requirements.txt
CMD ["python", "mysite/manage.py", "runserver", "0.0.0.0:8001"]

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Success looks like …

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Local storage
Docker
web
python manage.py runserver
db.sqlite3db.sqlite3
Local machine

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Moving to docker-compose
> touch docker-compose.yml
> docker-compose up
______docker-compose.yml__________________________________________________
version: "3"
services:
web:
build: .
command: python mysite/manage.py runserver 8001
ports:
- “8001:8001”
volumes:
- ./mysite/:/code
maps ports and container code/db to local filesystem

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Database service
Docker
web
python
manage.py
runserver
db
postgres
Local machine

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Adding a database service
______docker-compose.yml__________________________________________________
version: "3"
services:
web:
build: .
command: python mysite/manage.py runserver 8001
ports:
- “8001:8001”
volumes:
- ./mysite/:/code
db:
image: postgres
networks:
- backend
networks:
backend:
driver: bridge

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Handling env. variables
______settings.py____________________________________________________________
POSTGRES_PASSWORD = os.environ.get('POSTGRES_PASSWORD')
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'PASSWORD': POSTGRES_PASSWORD,
'HOST': ‘db',
'PORT': '5432',
},
______.env__________________________________________________________________
POSTGRES_PASSWORD=secret
POSTGRES_USER=postgres
DJANGO_SECRET_KEY=secret
> touch .env
> echo 'psycopg2-binary' >> requirements.txt

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Credentials in envvars
______docker-compose.yml__________________________________________________
version: "3"
services:
web:
[...]
environment:
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
POSTGRES_USER: ${POSTGRES_USER}
db:
[...]
environment:
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
POSTGRES_USER: ${POSTGRES_USER}

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Rebuilding the web image
______Dockerfile____________________________________________________________
FROM python:3.6.7-alpine
ENV PYTHONUNBUFFERED 1
RUN apk update &&
apk add --virtual build-deps gcc python-dev musl-dev &&
apk add postgresql-dev
RUN mkdir /code
WORKDIR /code
ADD ./ /code/
RUN pip install -r requirements.txt

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A bit of admin
> docker-compose exec web python mysite/manage.py migrate
> docker-compose exec web python mysite/manage.py createsuperuser
Run that every time we tear down our containers?
Note down the credentials we’ve used?

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Data migrations
______0001_initial.py___________________________________________________________
import os
from django.db import migrations
class Migration(migrations.Migration):
dependencies = []
def generate_superuser(apps, schema_editor):
from django.contrib.auth.models import User
DJANGO_SU_NAME = os.environ.get('DJANGO_SU_NAME')
DJANGO_SU_EMAIL = os.environ.get('DJANGO_SU_EMAIL')
DJANGO_SU_PASSWORD = os.environ.get('DJANGO_SU_PASSWORD')
superuser = User.objects.create_superuser(
username=DJANGO_SU_NAME, email=DJANGO_SU_EMAIL,
password=DJANGO_SU_PASSWORD)
superuser.save()
operations = [
migrations.RunPython(generate_superuser),
]

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More credentials
______docker-compose.yml__________________________________________________
version: "3"
services:
web:
[...]
environment:
DJANGO_DB_NAME: ${DJANGO_DB_NAME}
DJANGO_SU_NAME: ${DJANGO_SU_NAME}
DJANGO_SU_EMAIL: ${DJANGO_SU_EMAIL}
DJANGO_SU_PASSWORD: ${DJANGO_SU_PASSWORD}
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
POSTGRES_USER: ${POSTGRES_USER}

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web, db and admin services
Docker
web
python
manage.py
runserver
db
postgres
Local machine
db-admin
pgadmin server

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Adding a DB admin service
______docker-compose.yml__________________________________________________
[...]
db-admin:
image: dpage/pgadmin4
environment:
PGADMIN_DEFAULT_EMAIL: ${PGADMIN_DEFAULT_EMAIL}
PGADMIN_DEFAULT_PASSWORD: ${PGADMIN_DEFAULT_PASSWORD}
depends_on:
- db
ports:
- "8080:80"
networks:
- backend
[...]

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Local app for debugging
Docker
web
python
manage.py
runserver
db
postgres
Local machine
db-admin
pgadmin
server
python
manage.py
runserver

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Run a local app alongside
______settings.py____________________________________________________________
from decouple import config
SECRET_KEY = config(‘DJANGO_SECRET_KEY')
DEBUG = config('DJANGO_DEBUG', default=False, cast=bool)
WEB_HOST = config('DJANGO_WEB_HOST', default='localhost')
DB_HOST = config('DJANGO_DB_HOST', default='localhost')
DB_NAME = config(‘DJANGO_DB_NAME’)
[...]
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': POSTGRES_USER,
'PASSWORD': POSTGRES_PASSWORD,
'HOST': DB_HOST,
'PORT': '5432',
},

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Run a local app alongside
______docker-compose.yml_____________________________________
[...]
environment:
DJANGO_DEBUG: "True"
DJANGO_SECRET_KEY: ${DJANGO_SECRET_KEY}
DJANGO_DB_HOST: “db"
[...]

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With nginx
Docker
web
gunicorn
server
db
postgres
Local machine
db-admin
pgadmin
server
nginx
nginx
server
python
manage.py
runserver

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Add nginx server
______default.conf_______________________________
server {
listen 80;
server_name localhost;
location / {
proxy_pass http://web:8001;
}
}
______settings.py________________________________
[...]
ALLOWED_HOSTS = [WEB_HOST, ‘localhost']
[...]
> echo “gunicorn” >> requirements.txt

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Add nginx server
______docker-compose.yml__________________________________________________
[...]
web:
command: gunicorn mysite.wsgi --bind 0.0.0.0:8001
[...]
nginx:
image: nginx:latest
ports:
- 8088:80
volumes:
- ./nginx/default.conf:/etc/nginx/conf.d/default.conf
networks:
- backend
depends_on:
- web
[...]

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Static files & persistent data
Docker
web
gunicorn
server
db
postgres
Local machine
db-admin
pgadmin
server
nginx
nginx
server
python
manage.py
runserver
*.conf
+ static/
pg-data/

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Serving static assets
______settings.py_______________________________________
[...]
STATIC_ROOT = os.path.join(BASE_DIR, 'static')
> python mysite/manage.py collectstatic
______default.conf_____________________
server {
[...]
location /static {
alias /code/static;
}
}

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Serving static assets
______docker-compose.yml__________________________________________________
[...]
nginx:
[...]
volumes:
- ./nginx/default.conf:/etc/nginx/conf.d/default.conf
- ./mysite/static:/code/static
[...]
db:
volumes:
- ./postgres-data:/var/lib/postgresql/data
[...]

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Mapped ports
Docker
web
8001
db
5432
Local machine
db-admin
8080
nginx
8088
8000

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Logs

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Logging locally
• To STDOUT!

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Logs in shared envs
• Complex topic and no one size fits all
• Log aggregator (SumoLogic, Splunk, ELK etc.)
• A complete ELK stack in one container
• Various logging driver options
• Fluentd
• Gelf
Log aggregator
Fluentd
LogStash
ElasticSearch
Kibana

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Logging
Local machine
Staging environment
Build
server
Log aggregator
Production
Code
repo
Local machine
push
trigger
tail
deploy
stream
deploy
stream

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That’s all!
Thanks