def callback(self, timestamp, event_type, payload):
try:<EOL><INDENT>data = (event_type, payload)<EOL>LOG.debug('<STR_LIT>'<EOL>'<STR_LIT>', (<EOL>{'<STR_LIT>': event_type, '<STR_LIT>': payload}))<EOL>if '<STR_LIT>' in event_type:<EOL><INDENT>pri = self._create_pri<EOL><DEDENT>elif '<STR_LIT>' in event_type:<EOL><INDENT>pri = self._delete_pri<EOL><DEDENT>elif '<STR_LIT>' in event_type:<EOL><INDENT>pri = self._update_pri<EOL><DEDENT>else:<EOL><INDENT>pri = self._delete_pri<EOL><DEDENT>self._pq.put((pri, timestamp, data))<EOL><DEDENT>except Exception as exc:<EOL><INDENT>LOG.exception('<STR_LIT>',<EOL>{'<STR_LIT>': str(exc), '<STR_LIT>': event_type})<EOL><DEDENT>
Callback method for processing events in notification queue.

        :param timestamp: time the message is received.
        :param event_type: event type in the notification queue such as
                           identity.project.created, identity.project.deleted.
        :param payload: Contains information of an event