A feature flipper for Django.
Project description
Django Waffle is (yet another) feature flipper for Django. You can define the conditions for which a flag should be active, and use it in a number of ways.
Installation
To start using Waffle, you just need to add it to your INSTALLED_APPS and MIDDLEWARE_CLASSES:
INSTALLED_APPS = (
# ...
'waffle',
# ...
)
MIDDLEWARE_CLASSES = (
# ...
'waffle.middleware.WaffleMiddleware',
# ...
)
Since Waffle will be setting cookies on response objects, you probably want it below any middleware that tweaks cookies before sending them out.
Flags and Switches
Waffle supports two separate but ultimately similar concepts: Flags and Switches.
Basically, a Flag is tied to a request, while a Switch is not. Consequently, Flags are much more complicated, while Switches are basically just a named boolean in the database.
Flags
Creating and managing flags is done through the Django admin interface. Each feature flag is represented by a Flag object, which has several properties.
- Name:
The name of the flag. Will be used to identify the flag everywhere.
- Everyone:
You can flip this flag on (Yes) or off (No) for everyone, overriding all other settings. Leave as Unknown to use normally.
- Percent:
A percentage of users for whom the flag will be active. This is maintained through cookies, so clever users can get around it. Still, it’s the most common case.
- Superusers:
Is this flag always active for superusers?
- Staff:
Is this flag always active for staff?
- Authenticated:
Is this flag always active for authenticated users?
- Groups:
A list of group IDs for which this flag will always be active.
- Users:
A list of user IDs for which this flag will always be active.
- Rollout:
Activate Rollout mode? (See Rollout Mode below.)
You can combine multiple settings here. For example, you could offer a feature to 12% of users and all superusers. When combining settings, the flag will be active for the user if any of the settings matches for them.
Switches
New in 0.4!
Switches are also managed through the Django admin. Each Switch object has only two properties:
- Name:
The name of the switch.
- Active:
Is the switch active or inactive.
Like Flags, Switches can be used in views, templates, or wrapped around entire templates. But because they don’t rely on a request objects, Switches can also be used in crons, Celery tasks, daemons–basically anywhere you can access the database.
Using Waffle
Flags and Switches can be used in templates, in views, or wrapped around entire views.
If you try to use a flag or switch that is not defined, it will always be inactive.
Using Waffle in Templates
Jingo/Jinja2
To use a Flag in a Jinja2 template via Jingo, you can simply do:
{% if waffle_flag('flag_name') %}
Content if flag is active
{% endif %}
You can also add an {% else %} section, of course:
{% if waffle_flag('flag_name') %}
Flag is active!
{% else %}
Flag is inactive!
{% endif %}
To use a Switch in a Jinja2 template via Jingo, you can do:
{% if waffle_switch('switch_name') %}
Content if switch is active
{% endif %}
You can also add an {% else %} section, of course:
{% if waffle_switch('switch_name') %}
Switch is active!
{% else %}
Switch is inactive!
{% endif %}
Django Templates
To use a flag in vanilla Django templates, you can use the waffleflag tag:
{% load waffle_tags %}
{% waffleflag flag_name %}
Content if flag is active
{% endwaffleflag %}
The {% waffleflag %} tag also supports an {% else %} section:
{% waffleflag flag_name %}
Flag is active!
{% else %}
Flag is inactive!
{% endwaffleflag %}
To use a switch in vanilla Django templates, you can use the waffleswitch tag:
{% load waffle_tags %}
{% waffleswitch flag_name %}
Content if switch is active
{% endwaffleswitch %}
The {% waffleswitch %} tag also supports an {% else %} section:
{% waffleswitch flag_name %}
Switch is active!
{% else %}
Switch is inactive!
{% endwaffleswitch %}
Using Waffle in Views
To use a flag in a view, you just need waffle.flag_is_active:
import waffle
def my_view(request):
if waffle.flag_is_active(request, 'flag_name'):
# Behavior if flag is active.
else:
# Behavior if flag is inactive.
For switches, just use the switch_is_active method:
import waffle
def myview(request):
if waffle.switch_is_active('myswitch'):
return 'switch is active'
return 'switch is inactive'
Because it doesn’t need a request object, switch_is_active can be used anywhere.
Wraping a Whole View
You can also wrap an entire view in a flag:
from waffle.decorators import waffle_flag
@waffle_flag('flag_name')
def my_view(request):
# View only available if flag is active.
…or a switch:
from waffle.decorators import waffle_switch
@waffle_switch('switch_name')
def my_view(request):
# View only available if switch is active.
If the flag or switch is not active for the request, the view will be a 404.
You can reverse either decorator with an exclamation point at the start of the flag or switch name, for example:
@waffle_flag('!flag_name')
def my_view(request):
# View is only available if flag is INactive.
Global Settings
There are a few global settings you can define to adjust Waffle’s behavior.
Setting |
Default |
Description |
|---|---|---|
WAFFLE_COOKIE |
'dwf_%s' |
The format for the cookies Waffle sets. Must contain '%s'. |
WAFFLE_DEFAULT |
False |
By default, if a flag is undefined, Waffle treats it as inactive for everyone. Set this to True to treat undefined flags as active. |
WAFFLE_MAX_AGE |
2,529,000 |
How long should Waffle cookies last? (Integer, in seconds.) See the Cookies section. |
WAFFLE_OVERRIDE |
False |
Whether flags can be forced to be active from the query string. |
WAFFLE_SECURE |
False |
Whether to set the secure flag on cookies. |
Overriding Flags
If you turn on the WAFFLE_OVERRIDE setting, you can guarantee a flag will be active for a request by putting it in the query string.
For example, if I use the flag example in a view that serves the URL /search, then I can turn on the flag by adding ?example=1 to the query string, or turn it off by adding ?example=0.
By default, WAFFLE_OVERRIDE is off. It may be useful for testing, automated testing in particular.
Switches cannot be overridden at this time.
Rollout Mode
Rollout Mode allows you to gradually enable a feature for all users. In “normal” mode, a flag’s value will be set in a cookie until WAFFLE_MAX_AGE whether the flag is active or not. In Rollout Mode, an inactive flag will set a session cookie, and an active flag will set a longer-lived cookie.
Every time a user starts a new session, they’ll have a chance (determined by the percentage of the flag) to have the feature turned on “permanently”. Once it’s on, it should stay on, unless they clear their cookies or use a different browser (see To Do).
To guarantee an even rollout, it will likely be necessary to gradually increase the flag’s percentage as more and more users get stuck with the active cookie.
Rollout Mode is enabled per flag.
Waffle in JavaScript
Waffle now helps you use flags directly in JavaScript. You need to add the wafflejs view to your urls.py:
from waffle.views import wafflejs
urlpatterns = patterns('',
# ...
url(r'^wafflejs$', wafflejs, name='wafflejs'),
# ...
)
You can then load the Waffle JavaScript in your templates:
<script src="{% url wafflejs %}"></script>
Once you’ve loaded the JavaScript, you can use the global waffle object. Just pass in a flag name. As in the Python API, if a flag or switch is undefined, it will always be false.
if (waffle.flag('some_flag')) {
// Flag is active.
} else {
// Flag is inactive.
}
if (waffle.switch('some_switch')) {
// Switch is active.
} else {
// Switch is inactive.
}
To Do
Keep a flag setting for a given user, regardless of browser/device.
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