master_slave_connection.py 文件源码

def _send_message_with_response(self, message, _connection_to_use=None,
                                    _must_use_master=False, **kwargs):
        """Receive a message from Mongo.

        Sends the given message and returns a (connection_id, response) pair.

        :Parameters:
          - `operation`: opcode of the message to send
          - `data`: data to send
        """
        if _connection_to_use is not None:
            if _connection_to_use == -1:
                member = self.__master
                conn = -1
            else:
                member = self.__slaves[_connection_to_use]
                conn = _connection_to_use
            return (conn,
                    member._send_message_with_response(message, **kwargs)[1])

        # _must_use_master is set for commands, which must be sent to the
        # master instance. any queries in a request must be sent to the
        # master since that is where writes go.
        if _must_use_master or self.in_request():
            return (-1, self.__master._send_message_with_response(message,
                                                                  **kwargs)[1])

        # Iterate through the slaves randomly until we have success. Raise
        # reconnect if they all fail.
        for connection_id in helpers.shuffled(xrange(len(self.__slaves))):
            try:
                slave = self.__slaves[connection_id]
                return (connection_id,
                        slave._send_message_with_response(message,
                                                          **kwargs)[1])
            except AutoReconnect:
                pass

        raise AutoReconnect("failed to connect to slaves")