About

Django Triggers is a light-weight framework for having one part of an application generate a trigger while another part responds to to it. Triggers are persistent and can be scheduled to be processed at a later time.

Usage

Triggers are defined by subclassing the Trigger model. Trigger defines common data structures and logic for all child triggers. The only thing a child should have to do is override the _process method and set typed to a unique slug.

Settings

The following settings are used:

• DJTRIGGERS_TRIES_BEFORE_WARNING: the number of times a task can be retried before a warning is logged. Defaults to 3.
• DJTRIGGERS_TRIES_BEFORE_ERROR: the number of times a task can be retried before an error is raised. Defaults to 5.
• DJTRIGGERS_ASYNC_HANDLING: whether processing should be asynchronous (using Celery) or not. Default to False.
• DJTRIGGERS_CELERY_TASK_MAX_RETRIES: the number of times the Celery task for a trigger should be retried. Defaults to 0.
• DJTRIGGERS_TYPE_TO_TABLE: mapping of trigger types to database tables. Used for the cleanup script. Defaults to {}.
• DJTRIGGERS_REDIS_URL: the URL of the Redis instance used for locks.
• DJTRIGGERS_LOGGERS: separate logging config for django-triggers. Defaults to ().

Examples

General use

from djtriggers.models import Trigger

class BreakfastTrigger(Trigger):
    class Meta:
        # There is no trigger specific data so make a proxy model.
        # This ensures no additional db table is created.
        proxy = True
    typed = 'breakfast'

    def _process(self, dictionary={}):
        prepare_toast()
        prepare_juice()
        eat()

Trigger specific data

from djtriggers.models import Trigger

class PayBill(Trigger):
    class Meta:
        # We need a regular model as the trigger specific data needs a
        # place to live in the db.
        proxy = False

    amount = models.IntegerField()
    recipient = models.ForeignKey(User)

    def _process(self, dictionary={}):
        amount = self.amount
        recipient = self.recipient
        check_balance()
        pay_bill(amount, recipient)

Trigger processing

from .models import BreakfastTrigger
from .exceptions import ProcessError

trigger = BreakfastTrigger.objects.get(pk=1)
try:
    trigger.process()
except ProcessError as e:
    report_error(e)

Delayed processing

from .models import BreakfastTrigger

trigger = BreakfastTrigger()
# Process 8 hours later (this can be any datetime)
trigger.process_after = now() + timedelta(hour=8)