Django Finite State Machine Log

Automatic logging for the excellent Django FSM package.

Logs can be accessed before a transition occurs and before they are persisted to the database by enabling a cached backend. See Advanced Usage

Compatability

• Python 2.7 and 3.3+
• Django 1.6+
• South (if using 1.6) or 1.7 core migrations
• Django-FSM 2+

Installation

First, install the package with pip. This will automatically install any dependencies you may be missing

pip install django-fsm-log

Register django_fsm_log in your list of Django applications:

INSTALLED_APPS = (
    ...,
    'django_fsm_log',
    ...,
)

Then migrate the app to create the database table

python manage.py migrate django_fsm_log

Usage

The app will listen for django_fsm.signals.post_transition to be fired and create a new record for each transition.

To query logs simply

from django_fsm_log.models import StateLog
StateLog.objects.all()
# ...all recorded logs...

Disabling logging for specific models

By default transitions are logged for all models. Logging can be disabled for specific models by adding their fully qualified name to DJANGO_FSM_LOG_IGNORED_MODELS.

DJANGO_FSM_LOG_IGNORED_MODELS = ('poll.models.Vote')

for_ Manager Method

For convenience there is a custom for_ manager method to easily filter on the generic foreign key

from my_app.models import Article
from django_fsm_log.models import StateLog

article = Article.objects.all()[0]

StateLog.objects.for_(article)
# ...logs for article...

by Decorator

We found that our transitions are commonly called by a user, so we've added a decorator to make logging that painless

from django.db import models
from django_fsm import FSMField, transition
from django_fsm_log.decorators import fsm_log_by

class Article(models.Model):

    state = FSMField(default='draft', protected=True)

    @fsm_log_by
    @transition(field=state, source='draft', target='submitted')
    def submit(self, by=None):
        pass

Then every time the transition is called with the by kwarg set, it will be logged

article = Article.objects.create()
article.submit(by=some_user) # StateLog.by will be some_user

Advanced Usage

You can change the behaviour of this app by turning on caching for StateLog records. Simply add DJANGO_FSM_LOG_STORAGE_METHOD = 'django_fsm_log.backends.CachedBackend' to your project's settings file. It will use your project's default cache backend by default. If you wish to use a specific cache backend, you can add to your project's settings:

DJANGO_FSM_LOG_CACHE_BACKEND = 'some_other_cache_backend'

The StateLog object is now available after the django_fsm.signals.pre_transition signal is fired, but is deleted from the cache and persisted to the database after django_fsm.signals.post_transition is fired.

This is useful if:

• you need immediate access to StateLog details, and cannot wait until django_fsm.signals.post_transition has been fired
• at any stage, you need to verify whether or not the StateLog has been written to the database

Access to the pending StateLog record is available via the pending_objects manager

from django_fsm_log.models import StateLog
article = Article.objects.get(...)
pending_state_log = StateLog.pending_objects.get_for_object(article)

Running Tests

$ pip install tox
$ tox