Concurrency

Use ConcurrentTransitionMixin to avoid concurrent state changes. If the state changed in the database, django_fsm.ConcurrentTransition is raised on save().

from django_fsm import FSMField, ConcurrentTransitionMixin, FSMModelMixin

class BlogPost(ConcurrentTransitionMixin, FSMModelMixin, models.Model):
    state = FSMField(default='new')

For guaranteed protection against race conditions caused by concurrently executed transitions, make sure:

• Your transitions do not have side effects except for database changes.
• You always call save() within a django.db.transaction.atomic() block.

Following these recommendations, ConcurrentTransitionMixin will cause a rollback of all changes executed in an inconsistent state.