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nim-libp2p-experimental
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nim-libp2p-experimental/libp2p/protocols/pubsub/gossipsub.nim

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## 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* = 1.seconds
# 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
when defined(libp2p_expensive_metrics):
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
when defined(libp2p_expensive_metrics):
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
mesh = g.mesh.peers(topic)
gossipsub = g.gossipsub.peers(topic)
trace "rebalancing 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]())
)
shuffle(grafts)
# Graft peers so we reach a count of D
grafts.setLen(min(grafts.len, GossipSubD - g.mesh.peers(topic)))
trace "grafting", grafts = 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 "pruning", prunes = prunes.len
for peer in prunes:
g.mesh.removePeer(topic, peer)
when defined(libp2p_expensive_metrics):
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])
trace "mesh balanced"
# Send changes to peers after table updates to avoid stale state
if grafts.len > 0:
let graft = RPCMsg(control: some(ControlMessage(graft: @[ControlGraft(topicID: topic)])))
g.broadcast(grafts, graft)
if prunes.len > 0:
let prune = RPCMsg(control: some(ControlMessage(prune: @[ControlPrune(topicID: topic)])))
g.broadcast(prunes, prune)
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
when defined(libp2p_expensive_metrics):
libp2p_gossipsub_peers_per_topic_fanout
.set(g.fanout.peers(topic).int64, labelValues = [topic])
proc getGossipPeers(g: GossipSub): Table[PubSubPeer, 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 not mids.len > 0:
continue
if topic notin g.gossipsub:
trace "topic not in gossip array, skipping", topicID = topic
continue
let ihave = ControlIHave(topicID: topic, messageIDs: toSeq(mids))
for peer in allPeers:
if result.len >= GossipSubD:
trace "got gossip peers", peers = result.len
break
if peer in gossipPeers:
continue
if peer notin result:
result[peer] = controlMsg
result[peer].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()
for peer, control in peers:
g.peers.withValue(peer.peerId, pubsubPeer) do:
g.send(
pubsubPeer[],
RPCMsg(control: some(control)))
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 unsubscribePeer*(g: GossipSub, peer: PeerID) =
## handle peer disconnects
##
trace "unsubscribing gossipsub peer", peer = $peer
let pubSubPeer = g.peers.getOrDefault(peer)
if pubSubPeer.isNil:
return
for t in toSeq(g.gossipsub.keys):
g.gossipsub.removePeer(t, pubSubPeer)
when defined(libp2p_expensive_metrics):
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, pubSubPeer)
when defined(libp2p_expensive_metrics):
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, pubSubPeer)
when defined(libp2p_expensive_metrics):
libp2p_gossipsub_peers_per_topic_fanout
.set(g.fanout.peers(t).int64, labelValues = [t])
procCall FloodSub(g).unsubscribePeer(peer)
method subscribeTopic*(g: GossipSub,
topic: string,
subscribe: bool,
peer: PubSubPeer) {.gcsafe.} =
procCall FloodSub(g).subscribeTopic(topic, subscribe, peer)
logScope:
peer = $peer.id
topic
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)
when defined(libp2p_expensive_metrics):
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])
when defined(libp2p_expensive_metrics):
libp2p_gossipsub_peers_per_topic_gossipsub
.set(g.gossipsub.peers(topic).int64, labelValues = [topic])
trace "gossip peers", peers = g.gossipsub.peers(topic), 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))
when defined(libp2p_expensive_metrics):
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)
when defined(libp2p_expensive_metrics):
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,
rpcMsg: RPCMsg) {.async.} =
await procCall PubSub(g).rpcHandler(peer, rpcMsg)
if rpcMsg.messages.len > 0: # if there are any messages
var toSendPeers: HashSet[PubSubPeer]
for msg in rpcMsg.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.peerId):
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
await handleData(g, t, msg.data)
# forward the message to all peers interested in it
g.broadcast(
toSeq(toSendPeers),
RPCMsg(messages: rpcMsg.messages))
trace "forwared message to peers", peers = toSendPeers.len
if rpcMsg.control.isSome:
let control = rpcMsg.control.get()
g.handlePrune(peer, control.prune)
var respControl: ControlMessage
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 messages.len > 0:
debug "sending control message", msg = shortLog(respControl)
g.send(
peer,
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 (topic, handler) in topics:
# delete from mesh only if no handlers are left
if g.topics[topic].handler.len <= 0:
if topic in g.mesh:
let peers = g.mesh.getOrDefault(topic)
g.mesh.del(topic)
let prune = RPCMsg(control: some(ControlMessage(prune: @[ControlPrune(topicID: topic)])))
g.broadcast(toSeq(peers), prune)
method unsubscribeAll*(g: GossipSub, topic: string) {.async.} =
await procCall PubSub(g).unsubscribeAll(topic)
if topic in g.mesh:
let peers = g.mesh.getOrDefault(topic)
g.mesh.del(topic)
let prune = RPCMsg(control: some(ControlMessage(prune: @[ControlPrune(topicID: topic)])))
g.broadcast(toSeq(peers), prune)
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
if topic.len <= 0: # data could be 0/empty
return 0
var peers: HashSet[PubSubPeer]
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)
if peers.len > 0:
g.broadcast(toSeq(peers), RPCMsg(messages: @[msg]))
when defined(libp2p_expensive_metrics):
if peers.len > 0:
libp2p_pubsub_messages_published.inc(labelValues = [topic])
trace "published message to peers", peers = peers.len,
msg = msg.shortLog()
return peers.len
else:
debug "No peers for gossip message", topic, msg = msg.shortLog()
return 0
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()
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