Shout-out to eventlog

If you do things with the Django ORM and want an audit trails of all changes you have two options:

1. Insert some cleverness into a pre_save signal that writes down all changes some way.

2. Use eventlog and manually log things in your views.

(you have other options too but I'm trying to make a point here)

eventlog is almost embarrassingly simple. It's basically just a model with three fields:

• User
• An action string
• A JSON dump field

You use it like this:

from eventlog.models import log

def someview(request):
    if request.method == 'POST':
        form = SomeModelForm(request.POST)
        if form.is_valid():
            new_thing = form.save()
            log(request.user, 'mymodel.create', {
                'id': new_thing.id,
                'name': new_thing.name,
                # You can put anything JSON 
                # compatible in here
            })
            return redirect('someotherview')
    else:
        form = SomeModelForm()
    return render(request, 'view.html', {'form': form})

That's all it does. You then have to do something with it. Suppose you have an admin page that only privileged users can see. You can make a simple table/dashboard with these like this:

from eventlog.models import Log  # Log the model, not log the function

def all_events(request):
    all = Log.objects.all()
    return render(request, 'all_events.html', {'all': all})

And something like this to to all_events.html:

<table>
  <tr>
    <th>Who</th><th>When</th><th>What</th><th>Details</th>
  </tr>
  {% for event in all %}
  <tr>
    <td>{{ event.user.username }}</td>
    <td>{{ event.timestamp | date:"D d M Y" }}</td>
    <td>{{ event.action }}</td>
    <td>{{ event.extra }}</td>
  </tr>
  {% endfor %}
</table>

What I like about it is that it's very deliberate. By putting it into views at very specific points you're making it an audit log of actions, not of data changes.

Projects with overly complex model save signals tend to dig themselves into holes that make things slow and complicated. And it's not unrealistic that you'll then record events that aren't particularly important to review. For example, a cron job that increments a little value or something. It's more interesting to see what humans have done.

I just wanted to thank the Eldarion guys for eventlog. It's beautifully simple and works perfectly for me.