def start(self, fork=True):
        """Starts the registry aggregator.

        :param fork: whether to fork a process; if ``False``, blocks and stays in the existing process
        """
        if not fork:
            distributed_logger.info('Starting metrics aggregator, not forking')
            _registry_aggregator(self.reporter, self.socket_addr)
        else:
            distributed_logger.info('Starting metrics aggregator, forking')
            p = Process(target=_registry_aggregator, args=(self.reporter, self.socket_addr, ))
            p.start()
            distributed_logger.info('Started metrics aggregator as PID %s', p.pid)
            self.process = p
Starts the registry aggregator.

        :param fork: whether to fork a process; if ``False``, blocks and stays in the existing process