protocol.py 文件源码

def _write_header(self, buff, api_version=0, correlation_id=0):
        """Write the header for an outgoing message.

        :param buff: The buffer into which to write the header
        :type buff: buffer
        :param api_version: The "kafka api version id", used for feature flagging
        :type api_version: int
        :param correlation_id: This is a user-supplied integer. It will be
            passed back in the response by the server, unmodified. It is useful
            for matching request and response between the client and server.
        :type correlation_id: int
        """
        fmt = '!ihhih%ds' % len(self.CLIENT_ID)
        struct.pack_into(fmt, buff, 0,
                         len(buff) - 4,  # msglen excludes this int
                         self.API_KEY,
                         api_version,
                         correlation_id,
                         len(self.CLIENT_ID),
                         self.CLIENT_ID)