Download - Waffle: A feature switch/flag/toggle application for Django

Waffle

Toby Championgithub.com/tobych

Feature switches for Django

Feature branches are nasty

• Must deploy a branch to try things out• Unlikely to run full tests on a branch• Many branches: painful and confusing• Branching inhibits refactoring

Feature Switches

Allow you to include all new features on your master branch, hiding them from users so you can deploy all your code to production.

Now you can hide features!

• Features are developed in masteralongside others

• You have separate deploy and release steps• Your work need not impact users until ready• Leave branching just for spikes• Tests on master run on all features• Code is more often ready to deploy

Let’s use feature switches!

Use your switches everywhere

• Templates• JavaScript• Views• Models• Jinja2 templates (via Jingo)• Mustache/Handlebars templates• Management commands• Celery tasks

{% load waffle_tags %}

{% switch switch_name %} Switch is active!{% else %} Switch is inactive!{% endswitch %}

Django template

Wrap an entire view

JavaScript

Examples

Switchesshow_replace_buttonShow icon for incomplete feature

show_custom_fieldsShow custom fields on the edit dialog (delete this switch!)

no_fancy_tag_defaultsDisable broken JavaScript code until we fix it

debug_liveWrite extra live update debugging info to JavaScript console

use_reftag_kalman_filteringUse kalman filtering for reference tag barometer smoothing

Flags know about users and groups

Examples

Flagsshow_manage_rulesShow navigation item for new rule manager feature

use_selectionsUse new fancy check-box selection instead of drag’n’drop

no_xmppDon’t try to contact XMPP (BOSH) server at page load

no_mapsDon’t try to load map tiles at page load

Query string

http://example.com/?dwft_my_flag=0 – Offhttp://example.com/?dwft_my_flag=1 – On

Persisted for the session using cookies.

Also use Waffle for

• A/B testing (Waffle chooses randomly)• Canary releasing (roll out to % of users)

Be careful!

• Even inactive code can break your product• Unit tests must cover both cases• Integration tests should cover combinations• Remove unused switches! • Harder to follow code wrapped in switches

Persistence

• memcached• Redis

Waffle• http://coffeeonthekeyboard.com/introducing-waffle-for-django-541/• https://github.com/jsocol/django-waffle• http://waffle.readthedocs.org/

Feature Switches/Flags/Bits/Toggles• http://martinfowler.com/bliki/FeatureToggle.html• http://www.pgrs.net/2011/08/29/why-i-dont-like-feature-branches /• http://blog.disqus.com/post/789540337/partial-deployment-with-feature-switches• http://arialdomartini.wordpress.com/2011/11/02/help-me-because-i-think-martin-fowler-has-a-merge-paranoia/• http://www.youtube.com/watch?v=xzstASOvqNc• http://codeascraft.com/2011/02/04/how-does-etsy-manage-development-and-operations/• http://www.infoq.com/presentations/Feature-Bits

https://github.com/jsocol/django-waffle

https://github.com/jsocol/django-waffle

http://waffle.readthedocs.org/

http://www.pgrs.net/2011/08/29/why-i-dont-like-feature-branches/




http://blog.disqus.com/post/789540337/partial-deployment-with-feature-switches

http://arialdomartini.wordpress.com/2011/11/02/help-me-because-i-think-martin-fowler-has-a-merge-paranoia/

http://www.youtube.com/watch?v=xzstASOvqNc

http://codeascraft.com/2011/02/04/how-does-etsy-manage-development-and-operations/

http://www.infoq.com/presentations/Feature-Bits



Toby Champion

@tobychlinkedin.com/in/tobychampion

github.com/tobych/[email protected]

Seattle Python Day 2013

• Seattle Python Interest Group (SeaPIG)• Late September?• One day (Saturday)• Free or at least very cheap• Sprints on the Sunday?