On Condition

Run actions based on conditions.

Why?

To provide transparency into 'What happens When?' and 'Is This working?' when bundling arbitrary logic into your application. For example creating email notifications based on the form filledness criterias is a good use-case.

Environment Settings

CELERY_MODULE = "foo.app"

Optional Environment Settings

ET_MODEL = "oncondition.Event"
ET_WAITMODEL = "oncondition.EventWaiting"

Usage

An Event, that fires when any User has changes:

from oncondition.events import Event
class MyEvent(Event):
    def condition(self, instance, changes):
        return 5>4

    def action(self, instance, context):
        self.mail(subject='[EVENT] Breakthrough!', body="--", to=self.recipients())
        self.log("My Event fired! Recipients: [%s]"%self.recipients())

Register the Event:

from oncondition.events import event_model
event_model().objects.get_or_create(name="my-event", cls="project.MyEvent", model="auth.User", recipients="me@company.com,you@company.com")

Delayed Events

On Condition supports any number of CONDITION_NAME -methods to run for a single Event, with their respective (optional) 'CONDITION_NAME_failure' -methods. Out of the box time_condition has a respective time_condition_failure, that creates an EventWaiting -instance. This allows to poll changes to an Event out of a request/response cycle. When the time_condition is met, it is marked as done.

    CELERYBEAT_SCHEDULE = {
        'waiting-events': {
            'task': 'oncondition.tasks.handle_timed_events',
            'schedule': timedelta(minutes=60),
        }
    }

Project integration and testing

To test against Celery, provide your own CELERY_CONFIG_MODULE (see app_test_runner.py), eg:

# manage.py
    if 'test' in sys.argv:
        os.environ["CELERY_CONFIG_MODULE"] = "foo.tests.celeryconfig"
# foo.tests.celeryconfig
from foo.celeryconfig import *
CELERY_ALWAYS_EAGER = True
CELERY_EAGER_PROPAGATES_EXCEPTIONS = True

Best practices

Extend oncondition.models.Event and point ET_MODEL, ET_WAITMODEL to these.