Signalling Message

Implements a signalling message as a structured dataclass. Used to pass signaling message between the Django Message Broker clients and server.

class django_message_broker.server.signalling_message.SignallingMessageCommands

Valid message commands for signalling messages.

Client to server

  • GROUP_ADD (b”GROUPADD”) - Add a channel to a group.

  • GROUP_DISCARD (b”GROUPDIS”) - Remove a channel from a group.

  • FLUSH (b”FLUSHXXX”) - Remove all groups, subscriptions and messages from the server.

  • PRINT (b”PRINTXXX”) - Print contents of message store and group store to terminal.

  • PERFORMANCE (b”PERFMNCE”) - Request performance report

Server to client

  • COMPLETE (b”COMPLETE”) - Command complete

  • EXCEPTION (b”EXCEPTON”) - Command raised an exception.

  • PERFORMANCE_REPORT (b”PERFRPRT”) - Transmit performance report

  • FLUSH_CLIENT (b”FLUSHCXX”) - Flush client message store.

Both ways

  • KEEPALIVE (b”HARTBEAT”) - Intermittent message confirming client/server alive.

class django_message_broker.server.signalling_message.SignallingMessage(endpoints: typing.List = <factory>, id: bytes = <factory>, command: bytes = b'XXXXXXXX', properties: typing.Dict = <factory>)

Message is formatted on wire as n + 1 + 3 frames. Where n is the number of routing_ids added to the front of a message on zmq.DEALER to zmq.ROUTER messages; 1 is the null frame to separate routing_ids from the message; and 3 is the number of frames in the message.

  • frame -1:-n: Routing IDs (list of zmq.DEALER identities)

  • frame 0: b”” blank frame

  • frame 1: id - Unique universal identifier for tracking commands

  • frame 2: command - Message type (publish to channel, to group, subscribe to channel)

  • frame 3: properties - Properties appended to message

__getitem__(key: Union[int, str]) → Any

Returns values stored in the properties frame of the message.

Parameters

key (Union[int, str]) – Property key

Returns

Value stored in the property.

Return type

Optional[Any]

Raises

KeyError – If the key doesn’t exist.

get(key: Union[int, str], default: Optional[Any] = None) → Optional[Any]

Returns values stored in the properties frame of the message.

Parameters

  • key (Union[int, str]) – Property key.

  • default (Any, optional) – Default value if key doesn’t exist.

Returns

Property value if key exists, default or None if it doesn’t.

Return type

Optional[Any]

__setitem__(key: Union[int, str], value: Any) → None

Sets the value of a property in the properties frame of the message.

Parameters

  • key (Union[int, str]) – Property key

  • value (Any) – Value of the property (must be serialisable by msgspec)

__repr__() → str

Returns a printable string of signalling message contents.

Returns:

  • Endpoint list

  • Unique message id

  • Command

  • Properties

Returns

Signalling message contents.

Return type

str

async send(socket: Union[zmq.sugar.socket.Socket, zmq.eventloop.zmqstream.ZMQStream]) → None

Sends a message on the defined socket or stream.

Parameters

socket (Union[zmq.Socket, ZMQStream]) – Socket or stream on which message sent.

Raises
classmethod recv(socket: zmq.sugar.socket.Socket) → django_message_broker.server.signalling_message.SignallingMessage

Reads message from socket, returns new message instance.

classmethod from_msg(multipart_message: Union[_asyncio.Future, List]) → django_message_broker.server.signalling_message.SignallingMessage

Returns a new message instance from zmq multipart message frames.

Args:

multipart_message (Union[Future, List]): A list (or list in a Future) of zmq multipart frames.

Raises

MessageFormatException – If the number of frames in the multipart message doesn’t match the schema.

Returns

New instance of the message.

Return type

DataMessage