from ast import literal_eval import asyncio from collections import defaultdict import logging import random from typing import Any, DefaultDict, Dict, Iterable, List, Sequence, Set, Tuple from libp2p.network.stream.exceptions import StreamClosed from libp2p.peer.id import ID from libp2p.pubsub import floodsub from libp2p.typing import TProtocol from libp2p.utils import encode_varint_prefixed from .mcache import MessageCache from .pb import rpc_pb2 from .pubsub import Pubsub from .pubsub_router_interface import IPubsubRouter PROTOCOL_ID = TProtocol("/meshsub/1.0.0") logger = logging.getLogger("libp2p.pubsub.gossipsub") class GossipSub(IPubsubRouter): protocols: List[TProtocol] pubsub: Pubsub degree: int degree_high: int degree_low: int time_to_live: int mesh: Dict[str, Set[ID]] fanout: Dict[str, Set[ID]] # The protocol peer supports peer_protocol: Dict[ID, TProtocol] time_since_last_publish: Dict[str, int] mcache: MessageCache heartbeat_initial_delay: float heartbeat_interval: int def __init__( self, protocols: Sequence[TProtocol], degree: int, degree_low: int, degree_high: int, time_to_live: int, gossip_window: int = 3, gossip_history: int = 5, heartbeat_initial_delay: float = 0.1, heartbeat_interval: int = 120, ) -> None: self.protocols = list(protocols) self.pubsub = None # Store target degree, upper degree bound, and lower degree bound self.degree = degree self.degree_low = degree_low self.degree_high = degree_high # Store time to live (for topics in fanout) self.time_to_live = time_to_live # Create topic --> list of peers mappings self.mesh = {} self.fanout = {} # Create peer --> protocol mapping self.peer_protocol = {} # Create topic --> time since last publish map self.time_since_last_publish = {} # Create message cache self.mcache = MessageCache(gossip_window, gossip_history) # Create heartbeat timer self.heartbeat_initial_delay = heartbeat_initial_delay self.heartbeat_interval = heartbeat_interval # Interface functions def get_protocols(self) -> List[TProtocol]: """ :return: the list of protocols supported by the router """ return self.protocols def attach(self, pubsub: Pubsub) -> None: """ Attach is invoked by the PubSub constructor to attach the router to a freshly initialized PubSub instance. :param pubsub: pubsub instance to attach to """ self.pubsub = pubsub logger.debug("attached to pusub") # Start heartbeat now that we have a pubsub instance asyncio.ensure_future(self.heartbeat()) def add_peer(self, peer_id: ID, protocol_id: TProtocol) -> None: """ Notifies the router that a new peer has been connected. :param peer_id: id of peer to add :param protocol_id: router protocol the peer speaks, e.g., floodsub, gossipsub """ logger.debug("adding peer %s with protocol %s", peer_id, protocol_id) if protocol_id not in (PROTOCOL_ID, floodsub.PROTOCOL_ID): # We should never enter here. Becuase the `protocol_id` is registered by your pubsub # instance in multistream-select, but it is not the protocol that gossipsub supports. # In this case, probably we registered gossipsub to a wrong `protocol_id` # in multistream-select, or wrong versions. raise Exception(f"Unreachable: Protocol={protocol_id} is not supported.") self.peer_protocol[peer_id] = protocol_id def remove_peer(self, peer_id: ID) -> None: """ Notifies the router that a peer has been disconnected. :param peer_id: id of peer to remove """ logger.debug("removing peer %s", peer_id) for topic in self.mesh: self.mesh[topic].discard(peer_id) for topic in self.fanout: self.fanout[topic].discard(peer_id) self.peer_protocol.pop(peer_id, None) async def handle_rpc(self, rpc: rpc_pb2.RPC, sender_peer_id: ID) -> None: """ Invoked to process control messages in the RPC envelope. It is invoked after subscriptions and payload messages have been processed. :param rpc: RPC message :param sender_peer_id: id of the peer who sent the message """ control_message = rpc.control # Relay each rpc control message to the appropriate handler if control_message.ihave: for ihave in control_message.ihave: await self.handle_ihave(ihave, sender_peer_id) if control_message.iwant: for iwant in control_message.iwant: await self.handle_iwant(iwant, sender_peer_id) if control_message.graft: for graft in control_message.graft: await self.handle_graft(graft, sender_peer_id) if control_message.prune: for prune in control_message.prune: await self.handle_prune(prune, sender_peer_id) async def publish(self, msg_forwarder: ID, pubsub_msg: rpc_pb2.Message) -> None: """Invoked to forward a new message that has been validated.""" self.mcache.put(pubsub_msg) peers_gen = self._get_peers_to_send( pubsub_msg.topicIDs, msg_forwarder=msg_forwarder, origin=ID(pubsub_msg.from_id), ) rpc_msg = rpc_pb2.RPC(publish=[pubsub_msg]) logger.debug("publishing message %s", pubsub_msg) for peer_id in peers_gen: if peer_id not in self.pubsub.peers: continue stream = self.pubsub.peers[peer_id] # FIXME: We should add a `WriteMsg` similar to write delimited messages. # Ref: https://github.com/libp2p/go-libp2p-pubsub/blob/master/comm.go#L107 # TODO: Go use `sendRPC`, which possibly piggybacks gossip/control messages. try: await stream.write(encode_varint_prefixed(rpc_msg.SerializeToString())) except StreamClosed: logger.debug("Fail to publish message to %s: stream closed", peer_id) self.pubsub._handle_dead_peer(peer_id) def _get_peers_to_send( self, topic_ids: Iterable[str], msg_forwarder: ID, origin: ID ) -> Iterable[ID]: """ Get the eligible peers to send the data to. :param msg_forwarder: the peer id of the peer who forwards the message to me. :param origin: peer id of the peer the message originate from. :return: a generator of the peer ids who we send data to. """ send_to: Set[ID] = set() for topic in topic_ids: if topic not in self.pubsub.peer_topics: continue # floodsub peers floodsub_peers: Set[ID] = set( peer_id for peer_id in self.pubsub.peer_topics[topic] if self.peer_protocol[peer_id] == floodsub.PROTOCOL_ID ) send_to.update(floodsub_peers) # gossipsub peers gossipsub_peers: Set[ID] = set() if topic in self.mesh: gossipsub_peers = self.mesh[topic] else: # When we publish to a topic that we have not subscribe to, we randomly pick # `self.degree` number of peers who have subscribed to the topic and add them # as our `fanout` peers. topic_in_fanout: bool = topic in self.fanout fanout_peers: Set[ID] = self.fanout[topic] if topic_in_fanout else set() fanout_size = len(fanout_peers) if not topic_in_fanout or ( topic_in_fanout and fanout_size < self.degree ): if topic in self.pubsub.peer_topics: # Combine fanout peers with selected peers fanout_peers.update( self._get_in_topic_gossipsub_peers_from_minus( topic, self.degree - fanout_size, fanout_peers ) ) self.fanout[topic] = fanout_peers gossipsub_peers = fanout_peers send_to.update(gossipsub_peers) # Excludes `msg_forwarder` and `origin` yield from send_to.difference([msg_forwarder, origin]) async def join(self, topic: str) -> None: """ Join notifies the router that we want to receive and forward messages in a topic. It is invoked after the subscription announcement. :param topic: topic to join """ logger.debug("joining topic %s", topic) if topic in self.mesh: return # Create mesh[topic] if it does not yet exist self.mesh[topic] = set() topic_in_fanout: bool = topic in self.fanout fanout_peers: Set[ID] = self.fanout[topic] if topic_in_fanout else set() fanout_size = len(fanout_peers) if not topic_in_fanout or (topic_in_fanout and fanout_size < self.degree): # There are less than D peers (let this number be x) # in the fanout for a topic (or the topic is not in the fanout). # Selects the remaining number of peers (D-x) from peers.gossipsub[topic]. if topic in self.pubsub.peer_topics: selected_peers = self._get_in_topic_gossipsub_peers_from_minus( topic, self.degree - fanout_size, fanout_peers ) # Combine fanout peers with selected peers fanout_peers.update(selected_peers) # Add fanout peers to mesh and notifies them with a GRAFT(topic) control message. for peer in fanout_peers: self.mesh[topic].add(peer) await self.emit_graft(topic, peer) self.fanout.pop(topic, None) async def leave(self, topic: str) -> None: # Note: the comments here are the near-exact algorithm description from the spec """ Leave notifies the router that we are no longer interested in a topic. It is invoked after the unsubscription announcement. :param topic: topic to leave """ logger.debug("leaving topic %s", topic) if topic not in self.mesh: return # Notify the peers in mesh[topic] with a PRUNE(topic) message for peer in self.mesh[topic]: await self.emit_prune(topic, peer) # Forget mesh[topic] self.mesh.pop(topic, None) async def _emit_control_msgs( self, peers_to_graft: Dict[ID, List[str]], peers_to_prune: Dict[ID, List[str]], peers_to_gossip: Dict[ID, Dict[str, List[str]]], ) -> None: graft_msgs: List[rpc_pb2.ControlGraft] = [] prune_msgs: List[rpc_pb2.ControlPrune] = [] ihave_msgs: List[rpc_pb2.ControlIHave] = [] # Starting with GRAFT messages for peer, topics in peers_to_graft.items(): for topic in topics: graft_msg: rpc_pb2.ControlGraft = rpc_pb2.ControlGraft(topicID=topic) graft_msgs.append(graft_msg) # If there are also PRUNE messages to send to this peer if peer in peers_to_prune: for topic in peers_to_prune[peer]: prune_msg: rpc_pb2.ControlPrune = rpc_pb2.ControlPrune( topicID=topic ) prune_msgs.append(prune_msg) del peers_to_prune[peer] # If there are also IHAVE messages to send to this peer if peer in peers_to_gossip: for topic in peers_to_gossip[peer]: ihave_msg: rpc_pb2.ControlIHave = rpc_pb2.ControlIHave( messageIDs=peers_to_gossip[peer][topic], topicID=topic ) ihave_msgs.append(ihave_msg) del peers_to_gossip[peer] control_msg = self.pack_control_msgs(ihave_msgs, graft_msgs, prune_msgs) await self.emit_control_message(control_msg, peer) # Next with PRUNE messages for peer, topics in peers_to_prune.items(): prune_msgs = [] for topic in topics: prune_msg = rpc_pb2.ControlPrune(topicID=topic) prune_msgs.append(prune_msg) # If there are also IHAVE messages to send to this peer if peer in peers_to_gossip: ihave_msgs = [] for topic in peers_to_gossip[peer]: ihave_msg = rpc_pb2.ControlIHave( messageIDs=peers_to_gossip[peer][topic], topicID=topic ) ihave_msgs.append(ihave_msg) del peers_to_gossip[peer] control_msg = self.pack_control_msgs(ihave_msgs, None, prune_msgs) await self.emit_control_message(control_msg, peer) # Fianlly IHAVE messages for peer in peers_to_gossip: ihave_msgs = [] for topic in peers_to_gossip[peer]: ihave_msg = rpc_pb2.ControlIHave( messageIDs=peers_to_gossip[peer][topic], topicID=topic ) ihave_msgs.append(ihave_msg) control_msg = self.pack_control_msgs(ihave_msgs, None, None) await self.emit_control_message(control_msg, peer) # Heartbeat async def heartbeat(self) -> None: """ Call individual heartbeats. Note: the heartbeats are called with awaits because each heartbeat depends on the state changes in the preceding heartbeat """ # Start after a delay. Ref: https://github.com/libp2p/go-libp2p-pubsub/blob/01b9825fbee1848751d90a8469e3f5f43bac8466/gossipsub.go#L410 # Noqa: E501 await asyncio.sleep(self.heartbeat_initial_delay) while True: # Maintain mesh and keep track of which peers to send GRAFT or PRUNE to peers_to_graft, peers_to_prune = self.mesh_heartbeat() # Maintain fanout self.fanout_heartbeat() # Get the peers to send IHAVE to peers_to_gossip = self.gossip_heartbeat() # Pack GRAFT, PRUNE and IHAVE for the same peer into one control message and send it await self._emit_control_msgs( peers_to_graft, peers_to_prune, peers_to_gossip ) self.mcache.shift() await asyncio.sleep(self.heartbeat_interval) def mesh_heartbeat( self ) -> Tuple[DefaultDict[ID, List[str]], DefaultDict[ID, List[str]]]: peers_to_graft: DefaultDict[ID, List[str]] = defaultdict(list) peers_to_prune: DefaultDict[ID, List[str]] = defaultdict(list) for topic in self.mesh: # Skip if no peers have subscribed to the topic if topic not in self.pubsub.peer_topics: continue num_mesh_peers_in_topic = len(self.mesh[topic]) if num_mesh_peers_in_topic < self.degree_low: # Select D - |mesh[topic]| peers from peers.gossipsub[topic] - mesh[topic] selected_peers = self._get_in_topic_gossipsub_peers_from_minus( topic, self.degree - num_mesh_peers_in_topic, self.mesh[topic] ) for peer in selected_peers: # Add peer to mesh[topic] self.mesh[topic].add(peer) # Emit GRAFT(topic) control message to peer peers_to_graft[peer].append(topic) if num_mesh_peers_in_topic > self.degree_high: # Select |mesh[topic]| - D peers from mesh[topic] selected_peers = GossipSub.select_from_minus( num_mesh_peers_in_topic - self.degree, self.mesh[topic], set() ) for peer in selected_peers: # Remove peer from mesh[topic] self.mesh[topic].discard(peer) # Emit PRUNE(topic) control message to peer peers_to_prune[peer].append(topic) return peers_to_graft, peers_to_prune def fanout_heartbeat(self) -> None: # Note: the comments here are the exact pseudocode from the spec for topic in self.fanout: # Delete topic entry if it's not in `pubsub.peer_topics` # or if it's time-since-last-published > ttl # TODO: there's no way time_since_last_publish gets set anywhere yet if ( topic not in self.pubsub.peer_topics or self.time_since_last_publish[topic] > self.time_to_live ): # Remove topic from fanout del self.fanout[topic] del self.time_since_last_publish[topic] else: # Check if fanout peers are still in the topic and remove the ones that are not # ref: https://github.com/libp2p/go-libp2p-pubsub/blob/01b9825fbee1848751d90a8469e3f5f43bac8466/gossipsub.go#L498-L504 # noqa: E501 in_topic_fanout_peers = [ peer for peer in self.fanout[topic] if peer in self.pubsub.peer_topics[topic] ] self.fanout[topic] = set(in_topic_fanout_peers) num_fanout_peers_in_topic = len(self.fanout[topic]) # If |fanout[topic]| < D if num_fanout_peers_in_topic < self.degree: # Select D - |fanout[topic]| peers from peers.gossipsub[topic] - fanout[topic] selected_peers = self._get_in_topic_gossipsub_peers_from_minus( topic, self.degree - num_fanout_peers_in_topic, self.fanout[topic], ) # Add the peers to fanout[topic] self.fanout[topic].update(selected_peers) def gossip_heartbeat(self) -> DefaultDict[ID, Dict[str, List[str]]]: peers_to_gossip: DefaultDict[ID, Dict[str, List[str]]] = defaultdict(dict) for topic in self.mesh: msg_ids = self.mcache.window(topic) if msg_ids: # Get all pubsub peers in a topic and only add them if they are gossipsub peers too if topic in self.pubsub.peer_topics: # Select D peers from peers.gossipsub[topic] peers_to_emit_ihave_to = self._get_in_topic_gossipsub_peers_from_minus( topic, self.degree, self.mesh[topic] ) msg_id_strs = [str(msg_id) for msg_id in msg_ids] for peer in peers_to_emit_ihave_to: peers_to_gossip[peer][topic] = msg_id_strs # TODO: Refactor and Dedup. This section is the roughly the same as the above. # Do the same for fanout, for all topics not already hit in mesh for topic in self.fanout: msg_ids = self.mcache.window(topic) if msg_ids: # Get all pubsub peers in topic and only add if they are gossipsub peers also if topic in self.pubsub.peer_topics: # Select D peers from peers.gossipsub[topic] peers_to_emit_ihave_to = self._get_in_topic_gossipsub_peers_from_minus( topic, self.degree, self.fanout[topic] ) msg_id_strs = [str(msg) for msg in msg_ids] for peer in peers_to_emit_ihave_to: peers_to_gossip[peer][topic] = msg_id_strs return peers_to_gossip @staticmethod def select_from_minus( num_to_select: int, pool: Iterable[Any], minus: Iterable[Any] ) -> List[Any]: """ Select at most num_to_select subset of elements from the set (pool - minus) randomly. :param num_to_select: number of elements to randomly select :param pool: list of items to select from (excluding elements in minus) :param minus: elements to be excluded from selection pool :return: list of selected elements """ # Create selection pool, which is selection_pool = pool - minus if minus: # Create a new selection pool by removing elements of minus selection_pool: List[Any] = [x for x in pool if x not in minus] else: # Don't create a new selection_pool if we are not subbing anything selection_pool = list(pool) # If num_to_select > size(selection_pool), then return selection_pool (which has the most # possible elements s.t. the number of elements is less than num_to_select) if num_to_select >= len(selection_pool): return selection_pool # Random selection selection: List[Any] = random.sample(selection_pool, num_to_select) return selection def _get_in_topic_gossipsub_peers_from_minus( self, topic: str, num_to_select: int, minus: Iterable[ID] ) -> List[ID]: gossipsub_peers_in_topic = set( peer_id for peer_id in self.pubsub.peer_topics[topic] if self.peer_protocol[peer_id] == PROTOCOL_ID ) return self.select_from_minus(num_to_select, gossipsub_peers_in_topic, minus) # RPC handlers async def handle_ihave( self, ihave_msg: rpc_pb2.ControlIHave, sender_peer_id: ID ) -> None: """Checks the seen set and requests unknown messages with an IWANT message.""" # Get list of all seen (seqnos, from) from the (seqno, from) tuples in seen_messages cache seen_seqnos_and_peers = [ seqno_and_from for seqno_and_from in self.pubsub.seen_messages.keys() ] # Add all unknown message ids (ids that appear in ihave_msg but not in seen_seqnos) to list # of messages we want to request # FIXME: Update type of message ID msg_ids_wanted: List[Any] = [ msg_id for msg_id in ihave_msg.messageIDs if literal_eval(msg_id) not in seen_seqnos_and_peers ] # Request messages with IWANT message if msg_ids_wanted: await self.emit_iwant(msg_ids_wanted, sender_peer_id) async def handle_iwant( self, iwant_msg: rpc_pb2.ControlIWant, sender_peer_id: ID ) -> None: """Forwards all request messages that are present in mcache to the requesting peer.""" # FIXME: Update type of message ID # FIXME: Find a better way to parse the msg ids msg_ids: List[Any] = [literal_eval(msg) for msg in iwant_msg.messageIDs] msgs_to_forward: List[rpc_pb2.Message] = [] for msg_id_iwant in msg_ids: # Check if the wanted message ID is present in mcache msg: rpc_pb2.Message = self.mcache.get(msg_id_iwant) # Cache hit if msg: # Add message to list of messages to forward to requesting peers msgs_to_forward.append(msg) # Forward messages to requesting peer # Should this just be publishing? No # because then the message will forwarded to peers in the topics contained in the messages. # We should # 1) Package these messages into a single packet packet: rpc_pb2.RPC = rpc_pb2.RPC() packet.publish.extend(msgs_to_forward) # 2) Serialize that packet rpc_msg: bytes = packet.SerializeToString() # 3) Get the stream to this peer if sender_peer_id not in self.pubsub.peers: logger.debug( "Fail to responed to iwant request from %s: peer disconnected", sender_peer_id, ) return peer_stream = self.pubsub.peers[sender_peer_id] # 4) And write the packet to the stream try: await peer_stream.write(encode_varint_prefixed(rpc_msg)) except StreamClosed: logger.debug( "Fail to responed to iwant request from %s: stream closed", sender_peer_id, ) self.pubsub._handle_dead_peer(sender_peer_id) async def handle_graft( self, graft_msg: rpc_pb2.ControlGraft, sender_peer_id: ID ) -> None: topic: str = graft_msg.topicID # Add peer to mesh for topic if topic in self.mesh: if sender_peer_id not in self.mesh[topic]: self.mesh[topic].add(sender_peer_id) else: # Respond with PRUNE if not subscribed to the topic await self.emit_prune(topic, sender_peer_id) async def handle_prune( self, prune_msg: rpc_pb2.ControlPrune, sender_peer_id: ID ) -> None: topic: str = prune_msg.topicID # Remove peer from mesh for topic if topic in self.mesh: self.mesh[topic].discard(sender_peer_id) # RPC emitters def pack_control_msgs( self, ihave_msgs: List[rpc_pb2.ControlIHave], graft_msgs: List[rpc_pb2.ControlGraft], prune_msgs: List[rpc_pb2.ControlPrune], ) -> rpc_pb2.ControlMessage: control_msg: rpc_pb2.ControlMessage = rpc_pb2.ControlMessage() if ihave_msgs: control_msg.ihave.extend(ihave_msgs) if graft_msgs: control_msg.graft.extend(graft_msgs) if prune_msgs: control_msg.prune.extend(prune_msgs) return control_msg async def emit_ihave(self, topic: str, msg_ids: Any, to_peer: ID) -> None: """Emit ihave message, sent to to_peer, for topic and msg_ids.""" ihave_msg: rpc_pb2.ControlIHave = rpc_pb2.ControlIHave() ihave_msg.messageIDs.extend(msg_ids) ihave_msg.topicID = topic control_msg: rpc_pb2.ControlMessage = rpc_pb2.ControlMessage() control_msg.ihave.extend([ihave_msg]) await self.emit_control_message(control_msg, to_peer) async def emit_iwant(self, msg_ids: Any, to_peer: ID) -> None: """Emit iwant message, sent to to_peer, for msg_ids.""" iwant_msg: rpc_pb2.ControlIWant = rpc_pb2.ControlIWant() iwant_msg.messageIDs.extend(msg_ids) control_msg: rpc_pb2.ControlMessage = rpc_pb2.ControlMessage() control_msg.iwant.extend([iwant_msg]) await self.emit_control_message(control_msg, to_peer) async def emit_graft(self, topic: str, to_peer: ID) -> None: """Emit graft message, sent to to_peer, for topic.""" graft_msg: rpc_pb2.ControlGraft = rpc_pb2.ControlGraft() graft_msg.topicID = topic control_msg: rpc_pb2.ControlMessage = rpc_pb2.ControlMessage() control_msg.graft.extend([graft_msg]) await self.emit_control_message(control_msg, to_peer) async def emit_prune(self, topic: str, to_peer: ID) -> None: """Emit graft message, sent to to_peer, for topic.""" prune_msg: rpc_pb2.ControlPrune = rpc_pb2.ControlPrune() prune_msg.topicID = topic control_msg: rpc_pb2.ControlMessage = rpc_pb2.ControlMessage() control_msg.prune.extend([prune_msg]) await self.emit_control_message(control_msg, to_peer) async def emit_control_message( self, control_msg: rpc_pb2.ControlMessage, to_peer: ID ) -> None: # Add control message to packet packet: rpc_pb2.RPC = rpc_pb2.RPC() packet.control.CopyFrom(control_msg) rpc_msg: bytes = packet.SerializeToString() # Get stream for peer from pubsub if to_peer not in self.pubsub.peers: logger.debug( "Fail to emit control message to %s: peer disconnected", to_peer ) return peer_stream = self.pubsub.peers[to_peer] # Write rpc to stream try: await peer_stream.write(encode_varint_prefixed(rpc_msg)) except StreamClosed: logger.debug("Fail to emit control message to %s: stream closed", to_peer) self.pubsub._handle_dead_peer(to_peer)