py-libp2p/libp2p/pubsub/gossipsub.py
2019-07-23 23:00:43 +08:00

551 lines
22 KiB
Python

import random
import asyncio
from ast import literal_eval
from .pb import rpc_pb2
from .pubsub_router_interface import IPubsubRouter
from .mcache import MessageCache
class GossipSub(IPubsubRouter):
# pylint: disable=no-member
# pylint: disable=too-many-instance-attributes
# pylint: disable=too-many-public-methods
def __init__(self, protocols, degree, degree_low, degree_high, time_to_live, gossip_window=3,
gossip_history=5, heartbeat_interval=120):
# pylint: disable=too-many-arguments
self.protocols = protocols
self.pubsub = None
# Store target degree, upper degree bound, and lower degree bound
self.degree = degree
self.degree_high = degree_high
self.degree_low = degree_low
# 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 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):
"""
:return: the list of protocols supported by the router
"""
return self.protocols
def attach(self, pubsub):
"""
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, protocol_id):
"""
Notifies the router that a new peer has been connected
:param peer_id: id of peer to add
"""
# Add peer to the correct peer list
peer_type = GossipSub.get_peer_type(protocol_id)
peer_id_str = str(peer_id)
if peer_type == "gossip":
self.peers_gossipsub.append(peer_id_str)
elif peer_type == "flood":
self.peers_floodsub.append(peer_id_str)
def remove_peer(self, peer_id):
"""
Notifies the router that a peer has been disconnected
:param peer_id: id of peer to remove
"""
peer_id_str = str(peer_id)
self.peers_to_protocol.remove(peer_id_str)
async def handle_rpc(self, rpc, sender_peer_id):
"""
Invoked to process control messages in the RPC envelope.
It is invoked after subscriptions and payload messages have been processed
:param rpc: rpc message
"""
control_message = rpc.control
# Relay each rpc control 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, sender_peer_id, rpc_message):
# pylint: disable=too-many-locals
"""
Invoked to forward a new message that has been validated.
"""
packet = rpc_pb2.RPC()
packet.ParseFromString(rpc_message)
msg_sender = str(sender_peer_id)
# Deliver to self if self was origin
# Note: handle_talk checks if self is subscribed to topics in message
for message in packet.publish:
# Add RPC message to cache
self.mcache.put(message)
decoded_from_id = message.from_id.decode('utf-8')
new_packet = rpc_pb2.RPC()
new_packet.publish.extend([message])
new_packet_serialized = new_packet.SerializeToString()
# Deliver to self if needed
if msg_sender == decoded_from_id and msg_sender == str(self.pubsub.host.get_id()):
id_in_seen_msgs = (message.seqno, message.from_id)
if id_in_seen_msgs not in self.pubsub.seen_messages:
self.pubsub.seen_messages[id_in_seen_msgs] = 1
await self.pubsub.handle_talk(message)
# Deliver to peers
for topic in message.topicIDs:
# If topic has floodsub peers, deliver to floodsub peers
# TODO: This can be done more efficiently. Do it more efficiently.
floodsub_peers_in_topic = []
if topic in self.pubsub.peer_topics:
for peer in self.pubsub.peer_topics[topic]:
if str(peer) in self.peers_floodsub:
floodsub_peers_in_topic.append(peer)
await self.deliver_messages_to_peers(floodsub_peers_in_topic, msg_sender,
decoded_from_id, new_packet_serialized)
# If you are subscribed to topic, send to mesh, otherwise send to fanout
if topic in self.pubsub.my_topics and topic in self.mesh:
await self.deliver_messages_to_peers(self.mesh[topic], msg_sender,
decoded_from_id, new_packet_serialized)
else:
# Send to fanout peers
if topic not in self.fanout:
# If no peers in fanout, choose some peers from gossipsub peers in topic
gossipsub_peers_in_topic = [peer for peer in self.pubsub.peer_topics[topic]
if peer in self.peers_gossipsub]
selected = \
GossipSub.select_from_minus(self.degree, gossipsub_peers_in_topic, [])
self.fanout[topic] = selected
# TODO: 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
await self.deliver_messages_to_peers(self.fanout[topic], msg_sender,
decoded_from_id, new_packet_serialized)
async def join(self, topic):
# 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 = topic in self.fanout
fanout_peers = 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:
gossipsub_peers_in_topic = [peer for peer in self.pubsub.peer_topics[topic]
if peer in self.peers_gossipsub]
selected_peers = \
GossipSub.select_from_minus(self.degree - fanout_size,
gossipsub_peers_in_topic,
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):
# 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):
# 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, msg_sender, origin_id, serialized_packet):
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):
"""
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):
# 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:
gossipsub_peers_in_topic = [peer for peer in self.pubsub.peer_topics[topic]
if peer in self.peers_gossipsub]
# Select D - |mesh[topic]| peers from peers.gossipsub[topic] - mesh[topic]
selected_peers = GossipSub.select_from_minus(
self.degree - num_mesh_peers_in_topic,
gossipsub_peers_in_topic,
self.mesh[topic]
)
fanout_peers_not_in_mesh = [
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):
# 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]
self.time_since_last_publish.remove(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]
gossipsub_peers_in_topic = [peer for peer in self.pubsub.peer_topics[topic]
if peer in self.peers_gossipsub]
selected_peers = \
GossipSub.select_from_minus(self.degree - num_fanout_peers_in_topic,
gossipsub_peers_in_topic, self.fanout[topic])
# Add the peers to fanout[topic]
self.fanout[topic].extend(selected_peers)
async def gossip_heartbeat(self):
# pylint: disable=too-many-nested-blocks
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:
gossipsub_peers_in_topic = [peer for peer in self.pubsub.peer_topics[topic]
if peer in self.peers_gossipsub]
# Select D peers from peers.gossipsub[topic]
peers_to_emit_ihave_to = \
GossipSub.select_from_minus(self.degree, gossipsub_peers_in_topic, [])
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_ids = [str(msg) for msg in msg_ids]
await self.emit_ihave(topic, msg_ids, peer)
# 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:
gossipsub_peers_in_topic = [peer for peer in self.pubsub.peer_topics[topic]
if peer in self.peers_gossipsub]
# Select D peers from peers.gossipsub[topic]
peers_to_emit_ihave_to = \
GossipSub.select_from_minus(self.degree, gossipsub_peers_in_topic, [])
for peer in peers_to_emit_ihave_to:
if peer not in self.mesh[topic] and peer not in self.fanout[topic]:
msg_ids = [str(msg) for msg in msg_ids]
await self.emit_ihave(topic, msg_ids, peer)
self.mcache.shift()
@staticmethod
def select_from_minus(num_to_select, pool, minus):
"""
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 = [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 = 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 = random.sample(selection_pool, num_to_select)
return selection
# RPC handlers
async def handle_ihave(self, ihave_msg, sender_peer_id):
"""
Checks the seen set and requests unknown messages with an IWANT message.
"""
# from_id_bytes = ihave_msg.from_id
from_id_str = sender_peer_id
# 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
msg_ids_wanted = [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, from_id_str)
async def handle_iwant(self, iwant_msg, sender_peer_id):
"""
Forwards all request messages that are present in mcache to the requesting peer.
"""
from_id_str = sender_peer_id
msg_ids = [literal_eval(msg) for msg in iwant_msg.messageIDs]
msgs_to_forward = []
for msg_id_iwant in msg_ids:
# Check if the wanted message ID is present in mcache
msg = 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()
packet.publish.extend(msgs_to_forward)
# 2) Serialize that packet
rpc_msg = packet.SerializeToString()
# 3) Get the stream to this peer
# TODO: Should we pass in from_id or from_id_str here?
peer_stream = self.pubsub.peers[from_id_str]
# 4) And write the packet to the stream
await peer_stream.write(rpc_msg)
async def handle_graft(self, graft_msg, sender_peer_id):
topic = graft_msg.topicID
from_id_str = sender_peer_id
# Add peer to mesh for topic
if topic in self.mesh:
if from_id_str not in self.mesh[topic]:
self.mesh[topic].append(from_id_str)
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, sender_peer_id):
topic = prune_msg.topicID
from_id_str = sender_peer_id
# Remove peer from mesh for topic, if peer is in topic
if topic in self.mesh and from_id_str in self.mesh[topic]:
self.mesh[topic].remove(from_id_str)
# RPC emitters
async def emit_ihave(self, topic, msg_ids, to_peer):
"""
Emit ihave message, sent to to_peer, for topic and msg_ids
"""
ihave_msg = rpc_pb2.ControlIHave()
ihave_msg.messageIDs.extend(msg_ids)
ihave_msg.topicID = topic
control_msg = 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, to_peer):
"""
Emit iwant message, sent to to_peer, for msg_ids
"""
iwant_msg = rpc_pb2.ControlIWant()
iwant_msg.messageIDs.extend(msg_ids)
control_msg = rpc_pb2.ControlMessage()
control_msg.iwant.extend([iwant_msg])
await self.emit_control_message(control_msg, to_peer)
async def emit_graft(self, topic, to_peer):
"""
Emit graft message, sent to to_peer, for topic
"""
graft_msg = rpc_pb2.ControlGraft()
graft_msg.topicID = topic
control_msg = rpc_pb2.ControlMessage()
control_msg.graft.extend([graft_msg])
await self.emit_control_message(control_msg, to_peer)
async def emit_prune(self, topic, to_peer):
"""
Emit graft message, sent to to_peer, for topic
"""
prune_msg = rpc_pb2.ControlPrune()
prune_msg.topicID = topic
control_msg = 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, to_peer):
# Add control message to packet
packet = rpc_pb2.RPC()
packet.control.CopyFrom(control_msg)
rpc_msg = 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)