Gargoyle

Gargoyle is a platform built on top of Django which allows you to switch functionality of your application on and off based on conditions.

Installation

Install using pip:

pip install gargoyle-yplan

If you are upgrading from the original to this fork, you will need to run the following first, since the packages clash:

pip uninstall django-modeldict gargoyle

Failing to do this will mean that pip uninstall gargoyle will also erase the files for gargoyle-yplan, and similarly for our django-modeldict fork.

Enable Gargoyle

Once you’ve downloaded the Gargoyle package, you simply need to add it to your INSTALLED_APPS:

INSTALLED_APPS = (
    ...
    'gargoyle',
)

If you do not use Nexus, you will also need to enable discovery of gargoyle.py modules (which contain ConditionSets). The best place to do this is within your urls.py file:

import gargoyle

gargoyle.autodiscover()

If you do use gargoyle.py files, Python 2.7, and the autodiscovery code, you’ll need to ensure your imports are not relative:

from __future__ import absolute_import

from gargoyle.conditions import ConditionSet

Nexus Frontend

While Gargoyle can be used without a frontend, we highly recommend using Nexus.

Nexus will automatically detect Gargoyle’s NexusModule, assuming its autodiscovery is on. If not, you will need to register the module by hand:

from gargoyle.nexus_modules import GargoyleModule

nexus.site.register(GargoyleModule, 'gargoyle')

Disabling Auto Creation

Under some conditions you may not want Gargoyle to automatically create switches that don’t currently exist. To disable this behavior, you may use the GARGOYLE_AUTO_CREATE setting your settings.py:

GARGOYLE_AUTO_CREATE = False

Default Switch States

The GARGOYLE_SWITCH_DEFAULTS setting allows engineers to set the default state of a switch before it’s been added via the gargoyle admin interface. In your settings.py add something like:

GARGOYLE_SWITCH_DEFAULTS = {
    'new_switch': {
      'is_active': True,
      'label': 'New Switch',
      'description': 'When you want the newness',
    },
    'funky_switch': {
      'is_active': False,
      'label': 'Funky Switch',
      'description': 'Controls the funkiness.',
    },
}

Usage

Gargoyle is designed to work around a very simple API. Generally, you pass in the switch key and a list of instances to check this key against.

@switch_is_active

The simplest way to use Gargoyle is as a decorator. The decorator will automatically integrate with filters registered to the User model, as well as IP address (using RequestConditionSet):

from gargoyle.decorators import switch_is_active

@switch_is_active('my switch name')
def my_view(request):
    return 'foo'

In the case of the switch being inactive and you are using the decorator, a 404 error is raised. You may also redirect the user to an absolute URL (relative to domain), or a named URL pattern:

# If redirect_to starts with a /, we assume it's a url path
@switch_is_active('my switch name', redirect_to='/my/url/path')

# Alternatively use a name that will be passed to reverse()
@switch_is_active('my switch name', redirect_to='access_denied')

gargoyle.is_active

An alternative, more flexible use of Gargoyle is with the is_active method. This allows you to perform validation on your own custom objects:

from gargoyle import gargoyle

def my_function(request):
    if gargoyle.is_active('my switch name', request):
        return 'foo'
    else:
        return 'bar'

# with custom objects
from gargoyle import gargoyle

def my_method(user):
    if gargoyle.is_active('my switch name', user):
        return 'foo'
    else:
        return 'bar'

ifswitch

If you prefer to use templatetags, Gargoyle provides two helpers called ifswitch and ifnotswitch to give you easy conditional blocks based on active switches (for the request):

{% load gargoyle_tags %}

{% ifswitch switch_name %}
    switch_name is active!
{% else %}
    switch_name is not active :(
{% endifswitch %}

{% ifnotswitch other_switch_name %}
    other_switch_name is not active!
{% else %}
    other_switch_name is active!
{% endifnotswitch %}

The else clauses are optional.

ifswitch and ifnotswitch can also be used with custom objects, like the gargoyle.is_active method:

{% ifswitch "my switch name" user %}
    "my switch name" is active!
{% endifswitch %}

Switch Inheritance

Switches utilizing the named pattern of parent:child will automatically inherit state from their parents. For example, if your switch, parent:child is globally enabled, but parent is disabled, when is_active('parent:child') is called it will return False.

A parent switch that has its status set to ‘inherit’ will return the default value for a switch, which is False (the same as disabled).

Note

Currently inheritance does not combine filters. If your child defines any filters, they will override all of the parents.

Testing Switches

Gargoyle includes a context manager, which may optionally be used as a decorator, to give temporary state to a switch on the currently executing thread.

from gargoyle.testutils import switches

@switches(my_switch_name=True)
def test_switches_overrides():
    assert gargoyle.is_active('my_switch_name')  # passes

def test_switches_context_manager():
    with switches(my_switch_name=True):
        assert gargoyle.is_active('my_switch_name')  # passes

You may also optionally pass an instance of SwitchManager as the first argument:

def test_context_manager_alt_gargoyle():
    with switches(gargoyle, my_switch_name=True):
        assert gargoyle.is_active('my_switch_name')  # passes

API Reference

Condition Set API reference

This document describes the Condition Set API, which allows you to create your own custom switch validation logic.

Manager API reference

This document describes the Switch Manager API. This is generally referred to as the global gargoyle object, which lives in gargoyle.gargoyle.

class gargoyle.manager.SwitchManager(*args, **kwargs)
get_all_conditions()

Returns a generator which yields groups of lists of conditions.

>>> for set_id, label, field in gargoyle.get_all_conditions():
>>>     print("%(label)s: %(field)s" % (label, field.label))
get_condition_set_by_id(switch_id)

Given the identifier of a condition set (described in ConditionSet.get_id()), returns the registered instance.

get_condition_sets()

Returns a generator yielding all currently registered ConditionSet instances.

is_active(key, *instances, **kwargs)

Returns True if any of instances match an active switch. Otherwise returns False.

>>> gargoyle.is_active('my_feature', request)
register(condition_set)

Registers a condition set with the manager.

>>> condition_set = MyConditionSet()
>>> gargoyle.register(condition_set)
unregister(condition_set)

Unregisters a condition set with the manager.

>>> gargoyle.unregister(condition_set)

Switches are handled through the ModelDict interface, which is registered under the Switch model.

Signals

gargoyle.signals.switch_added

This signal is sent when a switch is added (similar to Django’s post_save, when created is True).

Example subscriber:

def switch_added_callback(sender, request, switch, **extra):
    logging.debug('Switch was added: %r', switch.label)

from gargoyle.signals import switch_added
switch_added.connect(switch_added_callback)
gargoyle.signals.switch_deleted

This signal is sent when a switch is deleted (similar to Django’s post_delete).

Example subscriber:

def switch_deleted_callback(sender, request, switch, **extra):
    logging.debug('Switch was deleted: %r', switch.label)

from gargoyle.signals import switch_deleted
switch_deleted.connect(switch_deleted_callback)
gargoyle.signals.switch_updated

This signal is sent when a switch is updated (similar to Django’s post_save, when created is False).

Example subscriber:

def switch_updated_callback(sender, request, switch, **extra):
    logging.debug('Switch was updated: %r', switch.label)

from gargoyle.signals import switch_updated
switch_updated.connect(switch_updated_callback)
gargoyle.signals.switch_status_updated

This signal is sent when a condition is updated in a switch.

Example subscriber:

def switch_status_updated_callback(sender, request, switch, status, **extra):
    logging.debug('Switch has updated status: %r; %r', switch.label, status)

from gargoyle.signals import switch_status_updated
switch_status_updated.connect(switch_status_updated_callback)
gargoyle.signals.switch_condition_added

This signal is sent when a condition is added to a switch.

Example subscriber:

def switch_condition_added_callback(sender, request, switch, condition, **extra):
    logging.debug('Switch has new condition: %r; %r', switch.label, condition)

from gargoyle.signals import switch_condition_added
switch_condition_added.connect(switch_condition_added_callback)
gargoyle.signals.switch_condition_deleted

This signal is sent when a condition is removed from a switch.

Example subscriber:

def switch_condition_deleted_callback(sender, request, switch, condition, **extra):
    logging.debug('Switch has deleted condition: %r; %r', switch.label, condition)

from gargoyle.signals import switch_condition_deleted
switch_condition_deleted.connect(switch_condition_deleted_callback)

Test Utilities

class gargoyle.testutils.SwitchContextManager(gargoyle=<SimpleLazyObject: <function make_gargoyle at 0x7f49461730c8>>, **keys)

Allows temporarily enabling or disabling a switch.

Ideal for testing.

>>> @switches(my_switch_name=True)
>>> def foo():
>>>     print(gargoyle.is_active('my_switch_name'))

>>> def foo():
>>>     with switches(my_switch_name=True):
>>>         print(gargoyle.is_active('my_switch_name'))

You may also optionally pass an instance of SwitchManager as the first argument.

>>> def foo():
>>>     with switches(gargoyle, my_switch_name=True):
>>>         print(gargoyle.is_active('my_switch_name'))