Making sure django model was properly saved

Question

When saving a django model using it's save method is there any way to make sure nothing happened during save and send a message to the user? I was thinking of the message framework and try except block?

try:
    model.save()
    add success message to message framework
except DatabaseError:
    add error message to message framework
except TransactionManagementError:
    add error message

Is this the right way to do that?Also which exception is more likely to be raised when trying to save a new instance of a model?I fairly new to django so be kind :)

Its cleaner to catch exception in view and put success/failure messages from there. — Rohan, Nov 11 '13 at 08:56

score 3 · Answer 1 · answered Nov 13 '13 at 10:22

My approach is to use a base abstract model that all my models extend and in which I override the save method in order to catch exceptions and rollback transactions:

class AbstractModel(models.Model):
    class Meta:
        abstract = True

    def save(self, force_insert=False, force_update=False, using=None, update_fields=None):
        try:
            super(AbstractModel, self).save(force_insert, force_update, using, update_fields)
        except IntegrityError as saveException:
            logger.exception('Rolling back transaction due to an error while saving %s...' % self.__class__.__name__)
            try:
                transaction.rollback()
            except Exception as rollbackException:
                logger.exception('Unable to rollback!')

score 1 · Answer 2 · answered Nov 13 '13 at 10:10

You would generally want to divide this to two problems:

Content problems, i.e. you have tried to save the same row in the db twice, triggering an error caused by a database constraint. This would raise a catchable IntegrityError. See: https://docs.djangoproject.com/en/dev/ref/exceptions/#database-exceptions (Django 1.6+ has some more errors). You should probably catch those and use something like messages.error to notify the user.
The database is down or having some other critical problem. You should probably avoid catching the errors, and let django handle it for you, and show your own 500 page until the db is back online. See: https://docs.djangoproject.com/en/dev/howto/error-reporting/ and https://docs.djangoproject.com/en/dev/ref/urls/#handler500

Is the TransactionManagementError the right exception for this job?I would like if django docs shared some real life case studies... — Apostolos, Nov 13 '13 at 10:36

Making sure django model was properly saved

2 Answers2