Tim Penhey: Deploying a Django application using Juju

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Tim Penhey:
Deploying a Django application using Juju
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@ Kiwi PyCon 2014 - Sunday, 14 Sep 2014 - Track 2
http://kiwi.pycon.org/

**Audience level**

Intermediate

**Description**

Juju is a service orchestration tool for deploying services into public or private clouds. I will talk about how I deployed my Django application using Juju.

**Abstract**

Juju is a service orchestration tool for deploying services into public or private clouds. The services that Juju deploys are described in Charms. A Charm should use the "best practice" for deploying the service. In the case of Django, this would be using gunicorn and nginx. I explain how the postgresql charm communicates with the django charm, and how I had to change my application's settings and urls to work with the django charm. The application that is deployed is a "proprietary" app, and as such, the deployment of the application itself is done with another charm. The interaction between the subordinate charms and the principal django charm are explained, and how the data is exchanged between the charms. As well as the deployment story, I also explain how application updates are deployed very simply.

**YouTube**

https://www.youtube.com/watch?v=6hc8VkFeHjA

Transcript

1. Deploying a Django based application with Juju Tim Penhey @howbazaar
2. or perhaps
3. How I used Juju to deploy our Django based website to Amazon EC2 Tim Penhey @howbazaar
4. • Not a Django talk • Not about how Juju works • Not lots of python code What this talk is not
5. Backstory • Rachel had this cool idea… • I said “I know how to do that…”
6. Backstory • Co-founded “know about when and where” (kawaw) with Rachel Saunders and Brenton Hall • Web site and mobile application combo • MVP ready… now what?
7. • Django • PostgreSQL • jQuery, backbone.js • PhoneGap The basics
8. Developing on my laptop We did what all developers did… ./manage.py runserver … but then, after a while … ./manage.py runserver_plus
9. Making it publicly visible Now we had real issues • keeping the site alive • backups • secure connections • scalability
10. Disclaimer I work for Canonical on the Juju project
11. What is Juju? • Service orchestration in the cloud Configure, manage, maintain, deploy and scale efficiently with best-practice Charms on any public, private or hybrid cloud from a powerful GUI or the command-line.
12. Charms give Juju its power • encapsulate application configurations • define how services get deployed • define how they connect to other services • know how to scale
13. but really… why?
15. Existing charms postgresql python-django gunicorn
16. Test deployment locally • deploy into LXC containers on my laptop • same charms are used • tests interaction
17. Juju can help with scaling later • Add ha-proxy, memcached • Multiple database servers • Scale out the application servers
18. Simple repeatable deployments • Repeatability is a key • New code as easy as upgrading a charm
19. however private codebase
20. Writing a subordinate charm • Simplest way to get code on to the same machine as the python-django charm was to write a subordinate charm • a.k.a. payload charm • puts the python code and resources into the right place on the disk
21. Hooks • install • config-changed • upgrade-charm • python-django-relation-joined • python-django-relation-changed
22. Hooks - continued • Hooks are just scripts • Juju is hook language agnostic • Just needs to be executable • I use python (with charm-helpers)
23. Hooks - reality • Install packages ◦ apt, pip ◦ install, upgrade-charm • Everything else ◦ copy code across ◦ config-changed, relationship hooks ◦ config-changed also gets called after upgrade- charm
24. Charm settings.py import glob from os.path import abspath, dirname, join PROJECT_DIR = abspath(dirname(__file__)) conffiles = glob.glob(join(PROJECT_DIR, '{{ dir }}', '*.py')) conffiles.sort() if not 'INSTALLED_APPS' in locals(): from django.conf.global_settings import * for f in conffiles: exec(open(abspath(f)).read())
25. First real code change • break up settings.py • charm makes files based on relationships or configuration settings ◦ config options ▪ 10-secret.py ▪ 30-allowed.py ▪ 40-debug.py ▪ 50-extra-config.py ◦ relationships - e.g. postgresql ▪ 20-engine-pgsql.py
26. Mirror the charm settings • Very similar base settings.py • Added settings dir ◦ 10-secret.py - SECRET_KEY ◦ 15-defaults.py - template loaders, base apps ◦ 20-database.py - local db settings ◦ 25-static-files.py - STATIC* settings ◦ 30-debug.py - DEBUG and TEMPLATE_DEBUG ◦ 40-project.py - root urls, wsgi app ◦ 45-debug-toolbar-juju.py ◦ 50-kawaw-juju.py ◦ 60-allauth-juju.py ◦ 70-logging-juju.py ◦ 80-email-juju.py
27. urls.py was next • Similar loading pattern for urls • Kinda makes sense for a framework charm
28. First deployment
30. Error • Improperly configured • hmm… more info needed • increased logging • turned on debug
31. Second deployment
33. Error • debug toolbar not configured • manual registration needed for urls if not using ./manage.py
34. Third deployment
36. Error • allauth not configured • hadn’t set up the google and facebook entries • oh yeah… • off to the admin interface
38. No CSS, no images • default static file serving not enabled with gunicorn • google suggests nginx
39. nginx • no promoted nginx charm • I wanted it to run beside the django charm • simplest approach was to roll it into the kawaw subordinate • added SSL • ./manage.py collectstatic --noinput
40. Fourth deployment
41. OMG - it worked!
42. kawaw charm makefile update-payload: @mkdir -p payload/ssl @cat ../../../requirements.txt | grep -v "^pytz" | grep -v "^psycopg2" > payload/requirements.txt @cp -r ../../../wit payload @cp ../../ssl/server.key payload/ssl @cp ../../ssl/kawaw.pem payload/ssl @rm -r payload/wit/fixtures
43. Deploying updated code $ juju upgrade-charm kawaw That’s it
44. Lessons learned
45. Lessons learned • insufficient documentation around using the python-django charm, had to read the code • insufficient documentation around how to write a payload charm for python-django, very much work it out as you go
46. Lessons learned • python-django and gunicorn still needs nginx to be really useful • should have a full stack django charm that includes gunicorn and nginx by default ◦ that just knows how to enable SSL for apps
47. Future work • PostgreSQL charm has daily backups by default, need to test restore • Database still lives on the ephemeral instance, need to move it elsewhere • Automated staging site based of production that has a copy of production database
48. Juju commands cd ~/src/wit/working/juju export JUJU_REPOSITORY=$(pwd) juju bootstrap --constraints 'mem=2048 root-disk=20G' juju deploy --to 0 cs:trusty/postgresql --config kawaw-prod.yaml juju deploy --to 0 local:python-django --config kawaw-prod.yaml juju deploy local:gunicorn juju add-relation postgresql:db python-django juju add-relation python-django gunicorn juju deploy local:kawaw juju add-relation python-django kawaw juju expose kawaw
49. Questions?