lockable_model.py

class LockableModel(TimeStampedModel):
    class Meta:
        abstract = True

    @ensure_atomic
    @contextmanager
    def get_exclusive_lock(self,
                           _connection=connection,
                           timeout=settings.PG_LOCKING_TIMEOUT_MS,
                           wait=True):
        cursor = _connection.cursor()
        # set timeout
        cursor.execute('SET LOCAL statement_timeout = %s;', (timeout,))
        # build the query
        sql = 'SELECT ctid from {table_name} WHERE id=%s FOR UPDATE'.format(
            table_name=self._meta.db_table
        )
        if not wait:
            sql += ' NOWAIT'

        try:
            # this will block untill timeout or the lock is aquired
            cursor.execute(sql, (self.pk,))
        except OperationalError:
            raise LockTakenException()
        else:
            yield True