Source code for tuna.zeromq.zmq_client

"""
This module's scope is the ZeroMQ client.
"""

import logging
import zmq

class zmq_client ( object ):
    """
    This class' responsibility is to define a ZeroMQ client that connects to a proxy to mediate communication with other clients.

    Utilizes the `lazy pirate pattern <http://zguide.zeromq.org/page:all#Client-Side-Reliability-Lazy-Pirate-Pattern>`_.
    """

    def __init__ ( self ):
        self.log = logging.getLogger ( )
        self.log.setLevel ( logging.DEBUG )

        self.zmq_context = zmq.Context ( )
        self.zmq_socket_req = None
        self.poller = None
        
    def close_socket ( self ):
        """
        This method's goal is to gracefully close the client connection with the proxy.
        """
        self.zmq_socket_req.setsockopt ( zmq.LINGER, 0 )
        self.zmq_socket_req.close ( )
        self.poller.unregister ( self.zmq_socket_req )

    def send ( self, message ):
        """
        This method's goal is to send a message to the proxy.

        Parameters:

        * message : string

        Returns:

        * string
            Containing the answer, which should be "ACK".
        """
        self.open_socket ( )
        self.register_poller ( )

        self.zmq_socket_req.send_unicode ( prefixed_msg )
        
        retries = 0
        answer = None
        while answer == None:
            answer = dict ( self.poller.poll ( 1000 ) )
            if answer.get ( self.zmq_socket_req ) == zmq.POLLIN:
                received = self.zmq_socket_req.recv ( )
                answer = received.decode ( 'utf-8' )
                if answer != 'ACK':
                    self.log ( 'Something is fishy!' )
                    self.log ( 'Received: "%s".' % answer.decode("utf-8") )
                    self.log ( "Expected: 'ACK'" )
            else:
                retries += 1
                self.open_socket ( )
                self.register_poller ( )
                suffixed_message = prefixed_msg + " (message resent " + str ( retries ) + " times)" 
                self.zmq_socket_req.send_unicode ( suffixed_message )

        self.close_socket ( )
        return answer

    def open_socket ( self ):
        """
        This method's goal is to gracefully open the connection with the ZeroMQ proxy.
        """
        self.zmq_socket_req = self.zmq_context.socket ( zmq.REQ )
        self.zmq_socket_req.connect ( "tcp://127.0.0.1:5000" )

    def register_poller ( self ):
        """
        This method's goal is to create a polling mechanism so that message passing is non-blocking.
        """
        self.poller = zmq.Poller ( )
        self.poller.register ( self.zmq_socket_req,
                               zmq.POLLIN )