Merge pull request #690 from mystical-prog/px-backoff

Peer Exchange and Back Off

Author: seetadev

libp2p/peer/peerinfo.py

@@ -66,5 +66,23 @@ def info_from_p2p_addr(addr: multiaddr.Multiaddr) -> PeerInfo:
     return PeerInfo(peer_id, [addr])
 
 
+def peer_info_to_bytes(peer_info: PeerInfo) -> bytes:
+    lines = [str(peer_info.peer_id)] + [str(addr) for addr in peer_info.addrs]
+    return "\n".join(lines).encode("utf-8")
+
+
+def peer_info_from_bytes(data: bytes) -> PeerInfo:
+    try:
+        lines = data.decode("utf-8").splitlines()
+        if not lines:
+            raise InvalidAddrError("no data to decode PeerInfo")
+
+        peer_id = ID.from_base58(lines[0])
+        addrs = [multiaddr.Multiaddr(addr_str) for addr_str in lines[1:]]
+        return PeerInfo(peer_id, addrs)
+    except Exception as e:
+        raise InvalidAddrError(f"failed to decode PeerInfo: {e}")
+
+
 class InvalidAddrError(ValueError):
     pass

libp2p/pubsub/gossipsub.py

@@ -32,6 +32,8 @@
 )
 from libp2p.peer.peerinfo import (
     PeerInfo,
+    peer_info_from_bytes,
+    peer_info_to_bytes,
 )
 from libp2p.peer.peerstore import (
     PERMANENT_ADDR_TTL,
@@ -92,6 +94,12 @@ class GossipSub(IPubsubRouter, Service):
     direct_connect_initial_delay: float
     direct_connect_interval: int
 
+    do_px: bool
+    px_peers_count: int
+    back_off: dict[str, dict[ID, int]]
+    prune_back_off: int
+    unsubscribe_back_off: int
+
     def __init__(
         self,
         protocols: Sequence[TProtocol],
@@ -106,6 +114,10 @@ def __init__(
         heartbeat_interval: int = 120,
         direct_connect_initial_delay: float = 0.1,
         direct_connect_interval: int = 300,
+        do_px: bool = False,
+        px_peers_count: int = 16,
+        prune_back_off: int = 60,
+        unsubscribe_back_off: int = 10,
     ) -> None:
         self.protocols = list(protocols)
         self.pubsub = None
@@ -140,6 +152,12 @@ def __init__(
         self.direct_connect_initial_delay = direct_connect_initial_delay
         self.time_since_last_publish = {}
 
+        self.do_px = do_px
+        self.px_peers_count = px_peers_count
+        self.back_off = dict()
+        self.prune_back_off = prune_back_off
+        self.unsubscribe_back_off = unsubscribe_back_off
+
     async def run(self) -> None:
         self.manager.run_daemon_task(self.heartbeat)
         if len(self.direct_peers) > 0:
@@ -334,15 +352,22 @@ async def join(self, topic: str) -> None:
         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_peers: set[ID] = set()
+
+        if topic_in_fanout:
+            for peer in self.fanout[topic]:
+                if self._check_back_off(peer, topic):
+                    continue
+                fanout_peers.add(peer)
+
         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:
+            if self.pubsub is not None and topic in self.pubsub.peer_topics:
                 selected_peers = self._get_in_topic_gossipsub_peers_from_minus(
-                    topic, self.degree - fanout_size, fanout_peers
+                    topic, self.degree - fanout_size, fanout_peers, True
                 )
                 # Combine fanout peers with selected peers
                 fanout_peers.update(selected_peers)
@@ -369,7 +394,8 @@ async def leave(self, topic: str) -> None:
             return
         # Notify the peers in mesh[topic] with a PRUNE(topic) message
         for peer in self.mesh[topic]:
-            await self.emit_prune(topic, peer)
+            await self.emit_prune(topic, peer, self.do_px, True)
+            self._add_back_off(peer, topic, True)
 
         # Forget mesh[topic]
         self.mesh.pop(topic, None)
@@ -505,7 +531,7 @@ def mesh_heartbeat(
             if num_mesh_peers_in_topic < self.degree_low:
                 # Select D - |mesh[topic]| peers from peers.gossipsub[topic] - mesh[topic]  # noqa: E501
                 selected_peers = self._get_in_topic_gossipsub_peers_from_minus(
-                    topic, self.degree - num_mesh_peers_in_topic, self.mesh[topic]
+                    topic, self.degree - num_mesh_peers_in_topic, self.mesh[topic], True
                 )
 
                 for peer in selected_peers:
@@ -568,9 +594,7 @@ def _handle_topic_heartbeat(
         if len(in_topic_peers) < self.degree:
             # Select additional peers from peers.gossipsub[topic]
             selected_peers = self._get_in_topic_gossipsub_peers_from_minus(
-                topic,
-                self.degree - len(in_topic_peers),
-                in_topic_peers,
+                topic, self.degree - len(in_topic_peers), in_topic_peers, True
             )
             # Add the selected peers
             in_topic_peers.update(selected_peers)
@@ -581,7 +605,7 @@ def _handle_topic_heartbeat(
             if msg_ids:
                 # Select D peers from peers.gossipsub[topic] excluding current peers
                 peers_to_emit_ihave_to = self._get_in_topic_gossipsub_peers_from_minus(
-                    topic, self.degree, current_peers
+                    topic, self.degree, current_peers, True
                 )
                 msg_id_strs = [str(msg_id) for msg_id in msg_ids]
                 for peer in peers_to_emit_ihave_to:
@@ -655,7 +679,11 @@ def select_from_minus(
         return selection
 
     def _get_in_topic_gossipsub_peers_from_minus(
-        self, topic: str, num_to_select: int, minus: Iterable[ID]
+        self,
+        topic: str,
+        num_to_select: int,
+        minus: Iterable[ID],
+        backoff_check: bool = False,
     ) -> list[ID]:
         if self.pubsub is None:
             raise NoPubsubAttached
@@ -664,8 +692,88 @@ def _get_in_topic_gossipsub_peers_from_minus(
             for peer_id in self.pubsub.peer_topics[topic]
             if self.peer_protocol[peer_id] == PROTOCOL_ID
         }
+        if backoff_check:
+            # filter out peers that are in back off for this topic
+            gossipsub_peers_in_topic = {
+                peer_id
+                for peer_id in gossipsub_peers_in_topic
+                if self._check_back_off(peer_id, topic) is False
+            }
         return self.select_from_minus(num_to_select, gossipsub_peers_in_topic, minus)
 
+    def _add_back_off(
+        self, peer: ID, topic: str, is_unsubscribe: bool, backoff_duration: int = 0
+    ) -> None:
+        """
+        Add back off for a peer in a topic.
+        :param peer: peer to add back off for
+        :param topic: topic to add back off for
+        :param is_unsubscribe: whether this is an unsubscribe operation
+        :param backoff_duration: duration of back off in seconds, if 0, use default
+        """
+        if topic not in self.back_off:
+            self.back_off[topic] = dict()
+
+        backoff_till = int(time.time())
+        if backoff_duration > 0:
+            backoff_till += backoff_duration
+        else:
+            if is_unsubscribe:
+                backoff_till += self.unsubscribe_back_off
+            else:
+                backoff_till += self.prune_back_off
+
+        if peer not in self.back_off[topic]:
+            self.back_off[topic][peer] = backoff_till
+        else:
+            self.back_off[topic][peer] = max(self.back_off[topic][peer], backoff_till)
+
+    def _check_back_off(self, peer: ID, topic: str) -> bool:
+        """
+        Check if a peer is in back off for a topic and cleanup expired back off entries.
+        :param peer: peer to check
+        :param topic: topic to check
+        :return: True if the peer is in back off, False otherwise
+        """
+        if topic not in self.back_off or peer not in self.back_off[topic]:
+            return False
+        if self.back_off[topic].get(peer, 0) > int(time.time()):
+            return True
+        else:
+            del self.back_off[topic][peer]
+            return False
+
+    async def _do_px(self, px_peers: list[rpc_pb2.PeerInfo]) -> None:
+        if len(px_peers) > self.px_peers_count:
+            px_peers = px_peers[: self.px_peers_count]
+
+        for peer in px_peers:
+            peer_id: ID = ID(peer.peerID)
+
+            if self.pubsub and peer_id in self.pubsub.peers:
+                continue
+
+            try:
+                peer_info = peer_info_from_bytes(peer.signedPeerRecord)
+                try:
+                    if self.pubsub is None:
+                        raise NoPubsubAttached
+                    await self.pubsub.host.connect(peer_info)
+                except Exception as e:
+                    logger.warning(
+                        "failed to connect to px peer %s: %s",
+                        peer_id,
+                        e,
+                    )
+                    continue
+            except Exception as e:
+                logger.warning(
+                    "failed to parse peer info from px peer %s: %s",
+                    peer_id,
+                    e,
+                )
+                continue
+
     # RPC handlers
 
     async def handle_ihave(
@@ -758,24 +866,46 @@ async def handle_graft(
                     logger.warning(
                         "GRAFT: ignoring request from direct peer %s", sender_peer_id
                     )
-                    await self.emit_prune(topic, sender_peer_id)
+                    await self.emit_prune(topic, sender_peer_id, False, False)
                     return
 
+            if self._check_back_off(sender_peer_id, topic):
+                logger.warning(
+                    "GRAFT: ignoring request from %s, back off until %d",
+                    sender_peer_id,
+                    self.back_off[topic][sender_peer_id],
+                )
+                self._add_back_off(sender_peer_id, topic, False)
+                await self.emit_prune(topic, sender_peer_id, False, False)
+                return
+
             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)
+            await self.emit_prune(topic, sender_peer_id, self.do_px, False)
 
     async def handle_prune(
         self, prune_msg: rpc_pb2.ControlPrune, sender_peer_id: ID
     ) -> None:
         topic: str = prune_msg.topicID
+        backoff_till: int = prune_msg.backoff
+        px_peers: list[rpc_pb2.PeerInfo] = []
+        for peer in prune_msg.peers:
+            px_peers.append(peer)
 
         # Remove peer from mesh for topic
         if topic in self.mesh:
+            if backoff_till > 0:
+                self._add_back_off(sender_peer_id, topic, False, backoff_till)
+            else:
+                self._add_back_off(sender_peer_id, topic, False)
+
             self.mesh[topic].discard(sender_peer_id)
 
+        if px_peers:
+            await self._do_px(px_peers)
+
     # RPC emitters
 
     def pack_control_msgs(
@@ -824,15 +954,36 @@ async def emit_graft(self, topic: str, id: ID) -> None:
 
         await self.emit_control_message(control_msg, id)
 
-    async def emit_prune(self, topic: str, id: ID) -> None:
+    async def emit_prune(
+        self, topic: str, to_peer: ID, do_px: bool, is_unsubscribe: bool
+    ) -> None:
         """Emit graft message, sent to to_peer, for topic."""
         prune_msg: rpc_pb2.ControlPrune = rpc_pb2.ControlPrune()
         prune_msg.topicID = topic
 
+        back_off_duration = self.prune_back_off
+        if is_unsubscribe:
+            back_off_duration = self.unsubscribe_back_off
+
+        prune_msg.backoff = back_off_duration
+
+        if do_px:
+            exchange_peers = self._get_in_topic_gossipsub_peers_from_minus(
+                topic, self.px_peers_count, [to_peer]
+            )
+            for peer in exchange_peers:
+                if self.pubsub is None:
+                    raise NoPubsubAttached
+                peer_info = self.pubsub.host.get_peerstore().peer_info(peer)
+                signed_peer_record: rpc_pb2.PeerInfo = rpc_pb2.PeerInfo()
+                signed_peer_record.peerID = peer.to_bytes()
+                signed_peer_record.signedPeerRecord = peer_info_to_bytes(peer_info)
+                prune_msg.peers.append(signed_peer_record)
+
         control_msg: rpc_pb2.ControlMessage = rpc_pb2.ControlMessage()
         control_msg.prune.extend([prune_msg])
 
-        await self.emit_control_message(control_msg, id)
+        await self.emit_control_message(control_msg, to_peer)
 
     async def emit_control_message(
         self, control_msg: rpc_pb2.ControlMessage, to_peer: ID

libp2p/pubsub/pb/rpc.proto

@@ -47,6 +47,13 @@ message ControlGraft {
 
 message ControlPrune {
 	optional string topicID = 1;
+	repeated PeerInfo peers = 2;
+	optional uint64 backoff = 3;
+}
+
+message PeerInfo {
+	optional bytes peerID = 1;
+	optional bytes signedPeerRecord = 2;
 }
 
 message TopicDescriptor {