py-libp2p/libp2p/pubsub/gossipsub.py
mhchia 4358a4bc89
Negotiate multiselect version for Muxer
`MuxerMultistream` is introduced to negotiate `Multiselect` version
before negotiating Multiplexer's version. This is required by
multistream 1.x
2019-08-21 11:43:24 +08:00

605 lines
23 KiB
Python

from ast import literal_eval
import asyncio
import random
from typing import Any, Dict, Iterable, List, Sequence, Set
from libp2p.peer.id import ID
from libp2p.typing import TProtocol
from .mcache import MessageCache
from .pb import rpc_pb2
from .pubsub import Pubsub
from .pubsub_router_interface import IPubsubRouter
class GossipSub(IPubsubRouter):
protocols: List[TProtocol]
pubsub: Pubsub
degree: int
degree_high: int
degree_low: int
time_to_live: int
mesh: Dict[str, List[ID]]
fanout: Dict[str, List[ID]]
peers_to_protocol: Dict[ID, str]
time_since_last_publish: Dict[str, int]
peers_gossipsub: List[ID]
peers_floodsub: List[ID]
mcache: MessageCache
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_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.peers_to_protocol = {}
# Create topic --> time since last publish map
self.time_since_last_publish = {}
self.peers_gossipsub = []
self.peers_floodsub = []
# Create message cache
self.mcache = MessageCache(gossip_window, gossip_history)
# Create heartbeat timer
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
# Start heartbeat now that we have a pubsub instance
# TODO: Start after delay
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
"""
# Add peer to the correct peer list
peer_type = GossipSub.get_peer_type(protocol_id)
self.peers_to_protocol[peer_id] = protocol_id
if peer_type == "gossip":
self.peers_gossipsub.append(peer_id)
elif peer_type == "flood":
self.peers_floodsub.append(peer_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
"""
del self.peers_to_protocol[peer_id]
if peer_id in self.peers_gossipsub:
self.peers_gossipsub.remove(peer_id)
if peer_id in self.peers_gossipsub:
self.peers_floodsub.remove(peer_id)
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])
for peer_id in peers_gen:
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.
await stream.write(rpc_msg.SerializeToString())
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
for peer_id in self.pubsub.peer_topics[topic]:
# FIXME: `gossipsub.peers_floodsub` can be changed to `gossipsub.peers` in go.
# This will improve the efficiency when searching for a peer's protocol id.
if peer_id in self.peers_floodsub:
send_to.add(peer_id)
# gossipsub peers
in_topic_gossipsub_peers: List[ID] = None
# TODO: Do we need to check `topic in self.pubsub.my_topics`?
if topic in self.mesh:
in_topic_gossipsub_peers = self.mesh[topic]
else:
# TODO(robzajac): Is topic DEFINITELY supposed to be in fanout if we are not
# subscribed?
# I assume there could be short periods between heartbeats where topic may not
# be but we should check that this path gets hit appropriately
if (topic not in self.fanout) or (len(self.fanout[topic]) == 0):
# If no peers in fanout, choose some peers from gossipsub peers in topic.
self.fanout[topic] = self._get_in_topic_gossipsub_peers_from_minus(
topic, self.degree, []
)
in_topic_gossipsub_peers = self.fanout[topic]
for peer_id in in_topic_gossipsub_peers:
send_to.add(peer_id)
# Excludes `msg_forwarder` and `origin`
yield from send_to.difference([msg_forwarder, origin])
async def join(self, topic: str) -> None:
# Note: the comments here are the near-exact algorithm description from the spec
"""
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
"""
if topic in self.mesh:
return
# Create mesh[topic] if it does not yet exist
self.mesh[topic] = []
topic_in_fanout: bool = topic in self.fanout
fanout_peers: List[ID] = self.fanout[topic] if topic_in_fanout else []
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 += selected_peers
# Add fanout peers to mesh and notifies them with a GRAFT(topic) control message.
for peer in fanout_peers:
if peer not in self.mesh[topic]:
self.mesh[topic].append(peer)
await self.emit_graft(topic, peer)
if topic_in_fanout:
del self.fanout[topic]
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
"""
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)
# Interface Helper Functions
@staticmethod
def get_peer_type(protocol_id: str) -> str:
# TODO: Do this in a better, more efficient way
if "gossipsub" in protocol_id:
return "gossip"
if "floodsub" in protocol_id:
return "flood"
return "unknown"
async def deliver_messages_to_peers(
self, peers: List[ID], msg_sender: ID, origin_id: ID, serialized_packet: bytes
) -> None:
for peer_id_in_topic in peers:
# Forward to all peers that are not the
# message sender and are not the message origin
if peer_id_in_topic not in (msg_sender, origin_id):
stream = self.pubsub.peers[peer_id_in_topic]
# Publish the packet
await stream.write(serialized_packet)
# 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
"""
while True:
await self.mesh_heartbeat()
await self.fanout_heartbeat()
await self.gossip_heartbeat()
await asyncio.sleep(self.heartbeat_interval)
async def mesh_heartbeat(self) -> None:
# Note: the comments here are the exact pseudocode from the spec
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]
)
fanout_peers_not_in_mesh: List[ID] = [
peer for peer in selected_peers if peer not in self.mesh[topic]
]
for peer in fanout_peers_not_in_mesh:
# Add peer to mesh[topic]
self.mesh[topic].append(peer)
# Emit GRAFT(topic) control message to peer
await self.emit_graft(topic, peer)
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], []
)
for peer in selected_peers:
# Remove peer from mesh[topic]
self.mesh[topic].remove(peer)
# Emit PRUNE(topic) control message to peer
await self.emit_prune(topic, peer)
async def fanout_heartbeat(self) -> None:
# Note: the comments here are the exact pseudocode from the spec
for topic in self.fanout:
# If time since last published > ttl
# TODO: there's no way time_since_last_publish gets set anywhere yet
if 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:
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].extend(selected_peers)
async def gossip_heartbeat(self) -> None:
for topic in self.mesh:
msg_ids = self.mcache.window(topic)
if msg_ids:
# TODO: Make more efficient, possibly using a generator?
# 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, []
)
for peer in peers_to_emit_ihave_to:
# TODO: this line is a monster, can hopefully be simplified
if (
topic not in self.mesh or (peer not in self.mesh[topic])
) and (
topic not in self.fanout or (peer not in self.fanout[topic])
):
msg_id_strs = [str(msg_id) for msg_id in msg_ids]
await self.emit_ihave(topic, msg_id_strs, peer)
# 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:
if topic not in self.mesh:
msg_ids = self.mcache.window(topic)
if msg_ids:
# TODO: Make more efficient, possibly using a generator?
# 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, []
)
for peer in peers_to_emit_ihave_to:
if (
peer not in self.mesh[topic]
and peer not in self.fanout[topic]
):
msg_id_strs = [str(msg) for msg in msg_ids]
await self.emit_ihave(topic, msg_id_strs, peer)
self.mcache.shift()
@staticmethod
def select_from_minus(
num_to_select: int, pool: Sequence[Any], minus: Sequence[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: Sequence[ID]
) -> List[ID]:
gossipsub_peers_in_topic = [
peer_id
for peer_id in self.pubsub.peer_topics[topic]
if peer_id in self.peers_gossipsub
]
return self.select_from_minus(
num_to_select, gossipsub_peers_in_topic, list(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
peer_stream = self.pubsub.peers[sender_peer_id]
# 4) And write the packet to the stream
await peer_stream.write(rpc_msg)
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].append(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 peer is in topic
if topic in self.mesh and sender_peer_id in self.mesh[topic]:
self.mesh[topic].remove(sender_peer_id)
# RPC emitters
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
peer_stream = self.pubsub.peers[to_peer]
# Write rpc to stream
await peer_stream.write(rpc_msg)