Channel Interface

class Channel(six.with_metaclass(abc.ABCMeta)):
    """Affords RPC invocation via generic methods on client-side.
    Channel objects implement the Context Manager type, although they need not
    support being entered and exited multiple times.
    """

    @abc.abstractmethod
    def subscribe(self, callback, try_to_connect=False):
        """Subscribe to this Channel's connectivity state machine.
        A Channel may be in any of the states described by ChannelConnectivity.
        This method allows application to monitor the state transitions.
        The typical use case is to debug or gain better visibility into gRPC
        runtime's state.
        Args:
          callback: A callable to be invoked with ChannelConnectivity argument.
            ChannelConnectivity describes current state of the channel.
            The callable will be invoked immediately upon subscription
            and again for every change to ChannelConnectivity until it
            is unsubscribed or this Channel object goes out of scope.
          try_to_connect: A boolean indicating whether or not this Channel
            should attempt to connect immediately. If set to False, gRPC
            runtime decides when to connect.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def unsubscribe(self, callback):
        """Unsubscribes a subscribed callback from this Channel's connectivity.
        Args:
          callback: A callable previously registered with this Channel from
          having been passed to its "subscribe" method.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def unary_unary(self,
                    method,
                    request_serializer=None,
                    response_deserializer=None):
        """Creates a UnaryUnaryMultiCallable for a unary-unary method.
        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None
            is passed.
        Returns:
          A UnaryUnaryMultiCallable value for the named unary-unary method.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def unary_stream(self,
                     method,
                     request_serializer=None,
                     response_deserializer=None):
        """Creates a UnaryStreamMultiCallable for a unary-stream method.
        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None is
            passed.
        Returns:
          A UnaryStreamMultiCallable value for the name unary-stream method.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def stream_unary(self,
                     method,
                     request_serializer=None,
                     response_deserializer=None):
        """Creates a StreamUnaryMultiCallable for a stream-unary method.
        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None is
            passed.
        Returns:
          A StreamUnaryMultiCallable value for the named stream-unary method.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def stream_stream(self,
                      method,
                      request_serializer=None,
                      response_deserializer=None):
        """Creates a StreamStreamMultiCallable for a stream-stream method.
        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None
            is passed.
        Returns:
          A StreamStreamMultiCallable value for the named stream-stream method.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def close(self):
        """Closes this Channel and releases all resources held by it.
        Closing the Channel will immediately terminate all RPCs active with the
        Channel and it is not valid to invoke new RPCs with the Channel.
        This method is idempotent.
        """
        raise NotImplementedError()

    def __enter__(self):
        """Enters the runtime context related to the channel object."""
        raise NotImplementedError()

    def __exit__(self, exc_type, exc_val, exc_tb):
        """Exits the runtime context related to the channel object."""
        raise NotImplementedError()