## Nim-LibP2P ## Copyright (c) 2019 Status Research & Development GmbH ## Licensed under either of ## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE)) ## * MIT license ([LICENSE-MIT](LICENSE-MIT)) ## at your option. ## This file may not be copied, modified, or distributed except according to ## those terms. import std/[tables, sets, options, sequtils, random] import chronos, chronicles, metrics import pubsub, floodsub, pubsubpeer, peertable, mcache, timedcache, rpc/[messages, message], ../protocol, ../../peerinfo, ../../stream/connection, ../../peerid, ../../errors, ../../utility logScope: topics = "gossipsub" const GossipSubCodec* = "/meshsub/1.0.0" # overlay parameters const GossipSubD* = 6 const GossipSubDlo* = 4 const GossipSubDhi* = 12 # gossip parameters const GossipSubHistoryLength* = 5 const GossipSubHistoryGossip* = 3 # heartbeat interval const GossipSubHeartbeatInitialDelay* = 100.millis const GossipSubHeartbeatInterval* = 5.seconds # TODO: per the spec it should be 1 second # fanout ttl const GossipSubFanoutTTL* = 1.minutes type GossipSub* = ref object of FloodSub mesh*: PeerTable # peers that we send messages to when we are subscribed to the topic fanout*: PeerTable # peers that we send messages to when we're not subscribed to the topic gossipsub*: PeerTable # peers that are subscribed to a topic lastFanoutPubSub*: Table[string, Moment] # last publish time for fanout topics gossip*: Table[string, seq[ControlIHave]] # pending gossip control*: Table[string, ControlMessage] # pending control messages mcache*: MCache # messages cache heartbeatFut: Future[void] # cancellation future for heartbeat interval heartbeatRunning: bool heartbeatLock: AsyncLock # heartbeat lock to prevent two consecutive concurrent heartbeats declareGauge(libp2p_gossipsub_peers_per_topic_mesh, "gossipsub peers per topic in mesh", labels = ["topic"]) declareGauge(libp2p_gossipsub_peers_per_topic_fanout, "gossipsub peers per topic in fanout", labels = ["topic"]) declareGauge(libp2p_gossipsub_peers_per_topic_gossipsub, "gossipsub peers per topic in gossipsub", labels = ["topic"]) method init*(g: GossipSub) = proc handler(conn: Connection, proto: string) {.async.} = ## main protocol handler that gets triggered on every ## connection for a protocol string ## e.g. ``/floodsub/1.0.0``, etc... ## await g.handleConn(conn, proto) g.handler = handler g.codec = GossipSubCodec proc replenishFanout(g: GossipSub, topic: string) = ## get fanout peers for a topic trace "about to replenish fanout" if g.fanout.peers(topic) < GossipSubDLo: trace "replenishing fanout", peers = g.fanout.peers(topic) if topic in g.gossipsub: for peer in g.gossipsub[topic]: if g.fanout.addPeer(topic, peer): if g.fanout.peers(topic) == GossipSubD: break libp2p_gossipsub_peers_per_topic_fanout .set(g.fanout.peers(topic).int64, labelValues = [topic]) trace "fanout replenished with peers", peers = g.fanout.peers(topic) proc rebalanceMesh(g: GossipSub, topic: string) {.async.} = logScope: topic trace "about to rebalance mesh" # create a mesh topic that we're subscribing to var grafts, prunes: seq[PubSubPeer] if g.mesh.peers(topic) < GossipSubDlo: trace "replenishing mesh", peers = g.mesh.peers(topic) # replenish the mesh if we're below Dlo grafts = toSeq( g.gossipsub.getOrDefault(topic, initHashSet[PubSubPeer]()) - g.mesh.getOrDefault(topic, initHashSet[PubSubPeer]()) ) logScope: meshPeers = g.mesh.peers(topic) grafts = grafts.len shuffle(grafts) # Graft peers so we reach a count of D grafts.setLen(min(grafts.len, GossipSubD - g.mesh.peers(topic))) trace "getting peers", topic, peers = grafts.len for peer in grafts: if g.mesh.addPeer(topic, peer): g.fanout.removePeer(topic, peer) if g.mesh.peers(topic) > GossipSubDhi: # prune peers if we've gone over Dhi prunes = toSeq(g.mesh[topic]) shuffle(prunes) prunes.setLen(prunes.len - GossipSubD) # .. down to D peers trace "about to prune mesh", prunes = prunes.len for peer in prunes: g.mesh.removePeer(topic, peer) libp2p_gossipsub_peers_per_topic_gossipsub .set(g.gossipsub.peers(topic).int64, labelValues = [topic]) libp2p_gossipsub_peers_per_topic_fanout .set(g.fanout.peers(topic).int64, labelValues = [topic]) libp2p_gossipsub_peers_per_topic_mesh .set(g.mesh.peers(topic).int64, labelValues = [topic]) # Send changes to peers after table updates to avoid stale state for p in grafts: await p.sendGraft(@[topic]) for p in prunes: await p.sendPrune(@[topic]) trace "mesh balanced, got peers", peers = g.mesh.peers(topic) proc dropFanoutPeers(g: GossipSub) = # drop peers that we haven't published to in # GossipSubFanoutTTL seconds let now = Moment.now() for topic in toSeq(g.lastFanoutPubSub.keys): let val = g.lastFanoutPubSub[topic] if now > val: g.fanout.del(topic) g.lastFanoutPubSub.del(topic) trace "dropping fanout topic", topic libp2p_gossipsub_peers_per_topic_fanout .set(g.fanout.peers(topic).int64, labelValues = [topic]) proc getGossipPeers(g: GossipSub): Table[string, ControlMessage] {.gcsafe.} = ## gossip iHave messages to peers ## trace "getting gossip peers (iHave)" let topics = toHashSet(toSeq(g.mesh.keys)) + toHashSet(toSeq(g.fanout.keys)) let controlMsg = ControlMessage() for topic in topics: var allPeers = toSeq(g.gossipsub.getOrDefault(topic)) shuffle(allPeers) let mesh = g.mesh.getOrDefault(topic) let fanout = g.fanout.getOrDefault(topic) let gossipPeers = mesh + fanout let mids = g.mcache.window(topic) if mids.len <= 0: continue let ihave = ControlIHave(topicID: topic, messageIDs: toSeq(mids)) if topic notin g.gossipsub: trace "topic not in gossip array, skipping", topicID = topic continue for peer in allPeers: if result.len >= GossipSubD: trace "got gossip peers", peers = result.len break if peer in gossipPeers: continue if peer.id notin result: result[peer.id] = controlMsg result[peer.id].ihave.add(ihave) proc heartbeat(g: GossipSub) {.async.} = while g.heartbeatRunning: try: trace "running heartbeat" for t in toSeq(g.topics.keys): await g.rebalanceMesh(t) g.dropFanoutPeers() # replenish known topics to the fanout for t in toSeq(g.fanout.keys): g.replenishFanout(t) let peers = g.getGossipPeers() var sent: seq[Future[void]] for peer in peers.keys: if peer in g.peers: sent &= g.peers[peer].send(RPCMsg(control: some(peers[peer]))) checkFutures(await allFinished(sent)) g.mcache.shift() # shift the cache except CancelledError as exc: raise exc except CatchableError as exc: trace "exception ocurred in gossipsub heartbeat", exc = exc.msg await sleepAsync(GossipSubHeartbeatInterval) method handleDisconnect*(g: GossipSub, peer: PubSubPeer) = ## handle peer disconnects procCall FloodSub(g).handleDisconnect(peer) for t in toSeq(g.gossipsub.keys): g.gossipsub.removePeer(t, peer) libp2p_gossipsub_peers_per_topic_gossipsub .set(g.gossipsub.peers(t).int64, labelValues = [t]) for t in toSeq(g.mesh.keys): g.mesh.removePeer(t, peer) libp2p_gossipsub_peers_per_topic_mesh .set(g.mesh.peers(t).int64, labelValues = [t]) for t in toSeq(g.fanout.keys): g.fanout.removePeer(t, peer) libp2p_gossipsub_peers_per_topic_fanout .set(g.fanout.peers(t).int64, labelValues = [t]) method subscribePeer*(p: GossipSub, conn: Connection) = procCall PubSub(p).subscribePeer(conn) asyncCheck p.handleConn(conn, GossipSubCodec) method subscribeTopic*(g: GossipSub, topic: string, subscribe: bool, peerId: string) {.gcsafe, async.} = await procCall FloodSub(g).subscribeTopic(topic, subscribe, peerId) logScope: peer = peerId topic let peer = g.peers.getOrDefault(peerId) if peer == nil: debug "subscribeTopic on a nil peer!" return if subscribe: trace "peer subscribed to topic" # subscribe remote peer to the topic discard g.gossipsub.addPeer(topic, peer) else: trace "peer unsubscribed from topic" # unsubscribe remote peer from the topic g.gossipsub.removePeer(topic, peer) g.mesh.removePeer(topic, peer) g.fanout.removePeer(topic, peer) libp2p_gossipsub_peers_per_topic_mesh .set(g.mesh.peers(topic).int64, labelValues = [topic]) libp2p_gossipsub_peers_per_topic_fanout .set(g.fanout.peers(topic).int64, labelValues = [topic]) libp2p_gossipsub_peers_per_topic_gossipsub .set(g.gossipsub.peers(topic).int64, labelValues = [topic]) trace "gossip peers", peers = g.gossipsub.peers(topic), topic # also rebalance current topic if we are subbed to if topic in g.topics: await g.rebalanceMesh(topic) proc handleGraft(g: GossipSub, peer: PubSubPeer, grafts: seq[ControlGraft]): seq[ControlPrune] = for graft in grafts: let topic = graft.topicID logScope: peer = peer.id topic trace "peer grafted topic" # If they send us a graft before they send us a subscribe, what should # we do? For now, we add them to mesh but don't add them to gossipsub. if topic in g.topics: if g.mesh.peers(topic) < GossipSubDHi: # In the spec, there's no mention of DHi here, but implicitly, a # peer will be removed from the mesh on next rebalance, so we don't want # this peer to push someone else out if g.mesh.addPeer(topic, peer): g.fanout.removePeer(topic, peer) else: trace "peer already in mesh" else: result.add(ControlPrune(topicID: topic)) else: debug "peer grafting topic we're not interested in" result.add(ControlPrune(topicID: topic)) libp2p_gossipsub_peers_per_topic_mesh .set(g.mesh.peers(topic).int64, labelValues = [topic]) libp2p_gossipsub_peers_per_topic_fanout .set(g.fanout.peers(topic).int64, labelValues = [topic]) proc handlePrune(g: GossipSub, peer: PubSubPeer, prunes: seq[ControlPrune]) = for prune in prunes: trace "peer pruned topic", peer = peer.id, topic = prune.topicID g.mesh.removePeer(prune.topicID, peer) libp2p_gossipsub_peers_per_topic_mesh .set(g.mesh.peers(prune.topicID).int64, labelValues = [prune.topicID]) proc handleIHave(g: GossipSub, peer: PubSubPeer, ihaves: seq[ControlIHave]): ControlIWant = for ihave in ihaves: trace "peer sent ihave", peer = peer.id, topic = ihave.topicID, msgs = ihave.messageIDs if ihave.topicID in g.mesh: for m in ihave.messageIDs: if m notin g.seen: result.messageIDs.add(m) proc handleIWant(g: GossipSub, peer: PubSubPeer, iwants: seq[ControlIWant]): seq[Message] = for iwant in iwants: for mid in iwant.messageIDs: trace "peer sent iwant", peer = peer.id, messageID = mid let msg = g.mcache.get(mid) if msg.isSome: result.add(msg.get()) method rpcHandler*(g: GossipSub, peer: PubSubPeer, rpcMsgs: seq[RPCMsg]) {.async.} = await procCall PubSub(g).rpcHandler(peer, rpcMsgs) for m in rpcMsgs: # for all RPC messages if m.messages.len > 0: # if there are any messages var toSendPeers: HashSet[PubSubPeer] for msg in m.messages: # for every message let msgId = g.msgIdProvider(msg) logScope: msgId if msgId in g.seen: trace "message already processed, skipping" continue trace "processing message" g.seen.put(msgId) # add the message to the seen cache if g.verifySignature and not msg.verify(peer.peerInfo): trace "dropping message due to failed signature verification" continue if not (await g.validate(msg)): trace "dropping message due to failed validation" continue # this shouldn't happen if g.peerInfo.peerId == msg.fromPeer: trace "skipping messages from self" continue for t in msg.topicIDs: # for every topic in the message if t in g.floodsub: toSendPeers.incl(g.floodsub[t]) # get all floodsub peers for topic if t in g.mesh: toSendPeers.incl(g.mesh[t]) # get all mesh peers for topic if t in g.topics: # if we're subscribed to the topic for h in g.topics[t].handler: trace "calling handler for message", topicId = t, localPeer = g.peerInfo.id, fromPeer = msg.fromPeer.pretty try: await h(t, msg.data) # trigger user provided handler except CatchableError as exc: trace "exception in message handler", exc = exc.msg # forward the message to all peers interested in it let published = await g.publishHelper(toSendPeers, m.messages) trace "forwared message to peers", peers = published var respControl: ControlMessage if m.control.isSome: let control = m.control.get() g.handlePrune(peer, control.prune) respControl.iwant.add(g.handleIHave(peer, control.ihave)) respControl.prune.add(g.handleGraft(peer, control.graft)) let messages = g.handleIWant(peer, control.iwant) if respControl.graft.len > 0 or respControl.prune.len > 0 or respControl.ihave.len > 0 or respControl.iwant.len > 0: await peer.send( RPCMsg(control: some(respControl), messages: messages)) method subscribe*(g: GossipSub, topic: string, handler: TopicHandler) {.async.} = await procCall PubSub(g).subscribe(topic, handler) await g.rebalanceMesh(topic) method unsubscribe*(g: GossipSub, topics: seq[TopicPair]) {.async.} = await procCall PubSub(g).unsubscribe(topics) for pair in topics: let topic = pair.topic if topic in g.mesh: let peers = g.mesh.getOrDefault(topic) g.mesh.del(topic) for peer in peers: await peer.sendPrune(@[topic]) method publish*(g: GossipSub, topic: string, data: seq[byte]): Future[int] {.async.} = # base returns always 0 discard await procCall PubSub(g).publish(topic, data) trace "publishing message on topic", topic, data = data.shortLog var peers: HashSet[PubSubPeer] if topic.len <= 0: # data could be 0/empty return 0 if topic in g.topics: # if we're subscribed use the mesh peers = g.mesh.getOrDefault(topic) else: # not subscribed, send to fanout peers # try optimistically peers = g.fanout.getOrDefault(topic) if peers.len == 0: # ok we had nothing.. let's try replenish inline g.replenishFanout(topic) peers = g.fanout.getOrDefault(topic) # even if we couldn't publish, # we still attempted to publish # on the topic, so it makes sense # to update the last topic publish # time g.lastFanoutPubSub[topic] = Moment.fromNow(GossipSubFanoutTTL) inc g.msgSeqno let msg = Message.init(g.peerInfo, data, topic, g.msgSeqno, g.sign) msgId = g.msgIdProvider(msg) trace "created new message", msg, topic, peers = peers.len if msgId notin g.mcache: g.mcache.put(msgId, msg) let published = await g.publishHelper(peers, @[msg]) if published > 0: libp2p_pubsub_messages_published.inc(labelValues = [topic]) trace "published message to peers", peers = published, msg = msg.shortLog() return published method start*(g: GossipSub) {.async.} = trace "gossipsub start" ## start pubsub ## start long running/repeating procedures # interlock start to to avoid overlapping to stops await g.heartbeatLock.acquire() # setup the heartbeat interval g.heartbeatRunning = true g.heartbeatFut = g.heartbeat() g.heartbeatLock.release() method stop*(g: GossipSub) {.async.} = trace "gossipsub stop" ## stop pubsub ## stop long running tasks await g.heartbeatLock.acquire() # stop heartbeat interval g.heartbeatRunning = false if not g.heartbeatFut.finished: trace "awaiting last heartbeat" await g.heartbeatFut trace "heartbeat stopped" g.heartbeatLock.release() method initPubSub*(g: GossipSub) = procCall FloodSub(g).initPubSub() randomize() g.mcache = newMCache(GossipSubHistoryGossip, GossipSubHistoryLength) g.mesh = initTable[string, HashSet[PubSubPeer]]() # meshes - topic to peer g.fanout = initTable[string, HashSet[PubSubPeer]]() # fanout - topic to peer g.gossipsub = initTable[string, HashSet[PubSubPeer]]()# topic to peer map of all gossipsub peers g.lastFanoutPubSub = initTable[string, Moment]() # last publish time for fanout topics g.gossip = initTable[string, seq[ControlIHave]]() # pending gossip g.control = initTable[string, ControlMessage]() # pending control messages g.heartbeatLock = newAsyncLock()