Django - leaving messages to (offline) users using the new messages framework

Question

So message_set is deprecated in favor of the new messages framework. The good old message_set allowed me to leave messages to offline users (for example, when I do some stuff in a cron job I may want to notify some user about that). Now take a glance at the new framework and it seems that a message can only be added to the request object.

Have I missed anything or is the functionality of adding a message to a user object gone, which means I'll have to roll my own?

Answer 1

The docs claim there are 4 different storage engines. The FallbackStorage engine writes to the session.

Answer 2

It doesn't look like you're missing anything. The functionality of adding messages to a user object will be deprecated in Django 1.2, and removed completely in 1.4 (from the django authentication docs here). And none of the new messaging storage backends are pre-rolled for persistent (e.g. database or file storage) of messages.

But all is not lost. I see nothing in the new messaging storage backend code that insists that you provide a valid request when storing a message (so storing a message from, for instance, a cron job would work). If I were you, I would roll my own backend that stashes messages in a database table.

Edit: How you might implement this

If your ok with implementing the offline message storage as a bolt on to one of the new messaging backends one possible approach is:

1. Define a message Model

   class UserMessage(models.Model):
     user = models.ForeignKey('auth.User')
     message = models.CharField(max_length=200)
     created = models.DateTimeField(auto_now_add=True)
   

2. Manually create UserMessages from your cron job

   def some_func_in_my_cron_job():
     ...
     UserMessage.create(user=some_user, message="Something happened")
     ...
   

3. Define a new message storage engine, overriding one of the existing engines, and redefine _get()

   from django.contrib.messages.storage.session import SessionStorage
   
   
   class MyStorageEngine(SessionStorage):
     _get(self, *args, **kwargs):
       if hasattr(self.request, "user") and self.request.user.is_authenticated():
           offline_messages = UserMessage.objects.filter(user=self.request.user)
           # and delete the messages from the database
       else:
           offline_messages = None
   
   
     other_messages = super(MyStorageEngine, self)._get(*args, **kwargs)
   
   
     # all_messages = combine offline_messages and other_messages
   
   
     return all_messages
   

4. Turn on your new message engine in settings:

   MESSAGE_STORAGE = 'myproj.custom_message_storage.MyStorageEngine'
   

With this approach, you won't write to your database backend using the new messaging api, but you can read your manually set messages with it. Hope this helps.