def handle_worker_messages(self, timeout):
        """
        Read messages that are placed in self.incoming_mailbox,
        and then update the job states corresponding to each message.

        Args:
            timeout: How long to wait for an incoming message, if the mailbox is empty right now.

        Returns: None

        """
        msgs = self.messaging_backend.popn(self.incoming_mailbox, n=20)

        for msg in msgs:
            self.handle_single_message(msg)