An introduction to Pallet and Forklift, a standard and tool for deploying and developing web applications on top of Docker.

1. Running Django
on Docker
a workflow and code
Alexey Kotlyarov • Danielle Madeley

2. The problem

5. A diverse world of
applications

6. Reproducible
deployments

9. Base OS (Debian bootstrap)
App dependencies
(Python, libs)
Built application
Transient runtime
Immutable
External
Storage

10. But there's no
standards!
12factor.net is a must read

11. Pallet
An interface for
Docker containers
github.com/infoxchange/pallet

12. What's in deploy?
database migrations
loading fixtures
install static content to static web server
(CDN, Ceph, nginx, etc.)

13. What's in serve?
Start app server
Starting supporting services, e.g. Celery

14. Keep it lean

15. $ docker build .

16. Dockerfile
FROM debian/ubuntu/fedora/etc.
RUN apt-get -qq update && apt-get -qq install
git mercurial
python python-virtualenv python-pip
...

17. RUN useradd -d /app -r app
WORKDIR /app

18. ADD requirements.txt /app/requirements.txt
RUN virtualenv python_env &&
. python_env/bin/activate &&
pip install -r requirements.txt
ADD . /app

19. VOLUME ["/static", "/storage"]
RUN mkdir -p /static /storage &&
chown -R app /static /storage

20. RUN echo "__version__ = '`git describe`'"
> myapp/__version__.py
RUN ./invoke.sh install
ENTRYPOINT ["./invoke.sh"]
EXPOSE 8000

21. invoke.sh
#!/bin/sh
# default parameters
: ${APP_USER:=app}
: ${WEB_CONCURRENCY:=1}
export WEB_CONCURRENCY
if [ "x$(whoami)" != "x$APP_USER" ]; then
# ensure we own our storage
chown -R "$APP_USER" /static /storage
# Call back into ourselves as the app user
exec sudo -sE -u "$APP_USER" -- "$0" "$@"
else

22. else
. ./startenv
case "$1" in
deploy)
shift 1 # consume command from $@
./manage.py migrate "$@"
;;
serve)
gunicorn -w "$WEB_CONCURRENCY"
-b 0.0.0.0:8000 "${APP}.wsgi:applicatio
;;
*)
./manage.py "$@"
;;
esac
fi

23. Django settings.py

24. from dj_database_url import parse
DATABASES = {
'default': parse(os.environ['DB_DEFAULT_URL']),
}

25. # Logging is complex
LOGGING['handlers']['logstash'] = {
'level': 'DEBUG' if DEBUG else 'INFO',
'class': 'logging.handlers.SysLogHandler',
'address': (os.environ['SYSLOG_SERVER'],
int(os.environ['SYSLOG_PORT']))
'socktype': socket.SOCK_STREAM
if os.environ['SYSLOG_PROTO'] ==
else socket.SOCK_DGRAM,
}

26. # Trust our nginx server
USE_X_FORWARDED_HOST = True
SECURE_PROXY_SSL_HEADER = ('HTTP_X_FORWARDED_PROTO',
MY_SITE_DOMAIN = os.environ.get('SITE_DOMAIN')
if MY_SITE_DOMAIN:
ALLOWED_HOSTS = (MY_SITE_DOMAIN,)

27. IXDjango
pallet configuration for
Django
pip install IXDjango
from ixdjango.docker_settings import *
github.com/infoxchange/ixdjango

28. An example
(in Flask)
github.com/danni/linux-conf-au-flask-
tute/tree/dockerify

29. Running the
container

30. docker run
-p 8000:8000
-e DB_DEFAULT_URL=postgres://user:pass@db3:5432/mya
-e SITE_DOMAIN=myapp-staging.company.com
-e SITE_PROTO=https
-e ENVIRONMENT=staging
-e ELASTICSEARCH_URLS=http://elastic-1:9200/myapp
-v /mnt/docker-storage/myapp:/storage
-h WHY_ARE_YOU_STILL_READING_THIS
myapp
serve

31. Urgh!

32. Forklift
a tool for loading pallets
github.com/infoxchange/docker-forklift

33. myapp/forklift.yaml
services:
- postgres
- elasticsearch

34. $ forklift myapp serve

35. Developing with
Forklift

36. $ forklift ./invoke.sh serve
$ forklift ./manage.py test

37. Poking around
inside containers
(aka troubleshooting)

38. $ forklift --mount-root
/tmp/myapp myapp sshd

39. Extending Forklift

40. forklift.services.memcache
@register('memcache')
class Memcache(Service):
providers = ('localhost', 'container')
DEFAULT_PORT = 11211
def __init__(self, key_prefix='', hosts=None):
self.key_prefix = key_prefix
self.hosts = hosts or []

41. def environment(self):
return {
'MEMCACHE_HOSTS': '|'.join(self.hosts),
'MEMCACHE_PREFIX': self.key_prefix,
}
def available(self):
"""
Check whether memcache is available
"""
...

42. @classmethod
def localhost(cls, application_id):
"""The default memcached provider"""
return cls(
key_prefix=application_id,
hosts=['localhost:{0}'.format(cls.DEFAULT

43. @classmethod
@transient_provider
def container(cls, application_id):
"""Memcached provided by a container."""
container = ensure_container(
image='fedora/memcached',
port=cls.DEFAULT_PORT,
application_id=application_id,
)
return cls(
key_prefix=application_id,
hosts=['localhost:{0}'.format(container.p
)

44. Continuous
integration

45. forklift --cleanroom myapp test

46. Legacy
applications

47. Fin ;-P
Questions?
github.com/infoxchange/pallet
github.com/infoxchange/docker-forklift