research/old_casper_poc1/casper.py

336 lines
13 KiB
Python

import copy, random, hashlib
from distributions import normal_distribution
import networksim
from voting_strategy import vote, default_vote
import math
# Number of validators
NUM_VALIDATORS = 20
# Block time
BLKTIME = 40
# 0 for no netsplits
# 1 for simulating a netsplit where 20% of validators jump off
# the network
# 2 for simulating the above netsplit, plus a 50-50 netsplit,
# plus reconvergence
NETSPLITS = 2
# Check the equality of finalized states
CHECK_INTEGRITY = True
# The genesis state root
GENESIS_STATE = 0
logging_level = 0
def log(s, lvl):
if logging_level >= lvl:
print(s)
# A signture specifies an initial height ("sign_from"), a finalized
# state from all blocks before that height and a list of probability
# bets from that height up to the latest height
class Signature():
def __init__(self, signer, probs, finalized_state, sign_from):
# The ID of the signer
self.signer = signer
# List of probability bets, expressed in log odds
self.probs = probs
# Hash of the signature (for db storage purposes)
self.hash = random.randrange(10**14)
# Finalized state
self.finalized_state = finalized_state
# Finalized height
self.sign_from = sign_from
def get_height(self):
return self.sign_from + len(self.probs)
# Right now, a block simply specifies a proposer and a height.
class Block():
def __init__(self, maker, height):
# The producer of the block
self.maker = maker
# The height of the block
self.height = height
# Hash of the signature (for db storage purposes)
self.hash = random.randrange(10**20) + 10**21 + 10**23 * self.height
# A request to receive a block at a particular height
class BlockRequest():
def __init__(self, sender, height):
self.sender = sender
self.ask_height = height
self.hash = random.randrange(10**14)
# Toy state transition function (in production, do sequential
# apply_transaction here)
def state_transition(state, block):
return state if block is None else (state ** 3 + block.hash ** 5) % 10**40
# A validator
class Validator():
def __init__(self, pos, network):
# Map from height to {node_id: latest_bet}
self.received_signatures = []
# List of received blocks
self.received_blocks = []
# Own probability estimates
self.probs = []
# All objects that this validator has received; basically a database
self.received_objects = {}
# Time when the object was received
self.time_received = {}
# The validator's ID, and its position in the queue
self.pos = self.id = pos
# The offset of this validator's clock vs. real time
self.time_offset = normal_distribution(0, 100)()
# The highest height that this validator has seen
self.max_height = 0
# The validator's hash chain
self.finalized_hashes = []
# Finalized states
self.finalized_states = []
# The highest height that the validator has finalized
self.max_finalized_height = -1
# The network object
self.network = network
# Last time signed
self.last_time_signed = 0
# Next height to mine
self.next_height = self.pos
# Get the local time from the point of view of this validator, using the
# validator's offset from real time
def get_time(self):
return self.network.time + self.time_offset
# Broadcast an object to the network
def broadcast(self, obj):
self.network.broadcast(self, obj)
# Create a signature
def sign(self):
# Initialize the probability array, the core of the signature
best_guesses = [None] * len(self.received_blocks)
sign_from = max(0, self.max_finalized_height - 30)
for i, b in list(enumerate(self.received_blocks))[sign_from:]:
# Compute this validator's own initial vote based on when the block
# was received, compared to what time the block should have arrived
received_time = self.time_received[b.hash] if b is not None else None
my_opinion = default_vote(BLKTIME * i, received_time, self.get_time(), blktime=BLKTIME)
# Get others' bets on this height
votes = self.received_signatures[i].values() if i < len(self.received_signatures) else []
votes = [x for x in votes if x != 0]
# Fill in the not-yet-received votes with this validator's default bet
votes += [my_opinion] * (NUM_VALIDATORS - len(votes))
vote_from_signatures = int(vote(votes))
# Add the bet to the list
bg = min(vote_from_signatures, 10 if self.received_blocks[i] is not None else my_opinion)
best_guesses[i] = bg
# Request a block if we should have it, and should have had it for
# a long time, but don't
if vote_from_signatures > 3 and self.received_blocks[i] is None:
self.broadcast(BlockRequest(self.id, i))
elif i < len(self.received_blocks) - 50 and self.received_blocks[i] is None:
if random.random() < 0.05:
self.broadcast(BlockRequest(self.id, i))
# Block finalized
if best_guesses[i] >= 10:
while len(self.finalized_hashes) <= i:
self.finalized_hashes.append(None)
self.finalized_hashes[i] = self.received_blocks[i].hash
# Absense of the block finalized
elif best_guesses[i] <= -10:
while len(self.finalized_hashes) <= i:
self.finalized_hashes.append(None)
self.finalized_hashes[i] = False
# Add to the list of finalized states
while self.max_finalized_height < len(self.finalized_hashes) - 1 \
and self.finalized_hashes[self.max_finalized_height + 1] is not None:
self.max_finalized_height += 1
last_state = self.finalized_states[-1] if len(self.finalized_states) else GENESIS_STATE
self.finalized_states.append(state_transition(last_state, self.received_blocks[self.max_finalized_height]))
self.probs = self.probs[:sign_from] + best_guesses[sign_from:]
log('Making signature: %r' % self.probs[-10:], lvl=1)
sign_from_state = self.finalized_states[sign_from - 1] if sign_from > 0 else GENESIS_STATE
s = Signature(self.pos, self.probs[sign_from:], sign_from_state, sign_from)
all_signatures.append(s)
return s
def on_receive(self, obj):
# Ignore objects that we already know about
if obj.hash in self.received_objects:
return
# When receiving a block
if isinstance(obj, Block):
log('received block: %d %d' % (obj.height, obj.hash), lvl=2)
while len(self.received_blocks) <= obj.height:
self.received_blocks.append(None)
self.received_blocks[obj.height] = obj
self.time_received[obj.hash] = self.get_time()
# Upon receiving a new block, make a new signature
s = self.sign()
self.network.broadcast(self, s)
self.on_receive(s)
self.network.broadcast(self, obj)
# When receiving a signature
elif isinstance(obj, Signature):
while len(self.received_signatures) <= len(obj.probs) + obj.sign_from:
self.received_signatures.append({})
for i, p in enumerate(obj.probs):
self.received_signatures[i + obj.sign_from][obj.signer] = p
self.network.broadcast(self, obj)
# Received a block request, respond if we have it
elif isinstance(obj, BlockRequest):
if obj.ask_height < len(self.received_blocks):
if self.received_blocks[obj.ask_height] is not None:
self.network.direct_send(obj.sender, self.received_blocks[obj.ask_height])
self.received_objects[obj.hash] = obj
self.time_received[obj.hash] = self.get_time()
# Run every tick
def tick(self):
mytime = self.get_time()
target_time = BLKTIME * self.next_height
if mytime >= target_time:
o = Block(self.pos, self.next_height)
self.next_height += NUM_VALIDATORS
log('making block: %d %d' % (o.height, o.hash), lvl=1)
if random.random() < 0.9:
self.network.broadcast(self, o)
while len(self.received_blocks) <= o.height:
self.received_blocks.append(None)
self.received_blocks[o.height] = o
self.received_objects[o.hash] = o
self.time_received[o.hash] = mytime
return o
validator_list = []
future = {}
discarded = {}
finalized_blocks = {}
all_signatures = []
now = [0]
def who_heard_of(h, n):
o = ''
for x in n.agents:
o += '1' if h in x.received_objects else '0'
return o
def get_opinions(n):
o = []
maxheight = 0
for x in n.agents:
maxheight = max(maxheight, len(x.probs))
for h in range(maxheight):
p = ''
q = ''
for x in n.agents:
if len(x.probs) <= h:
p += '_'
elif x.probs[h] <= -10:
p += '-'
elif x.probs[h] >= 10:
p += '+'
else:
p += str(x.probs[h])+','
q += 'n' if len(x.received_blocks) <= h or x.received_blocks[h] is None else 'y'
o.append((h, p, q))
return o
def get_finalization_heights(n):
o = []
for x in n.agents:
o.append(x.max_finalized_height)
return o
# Check how often blocks that are assigned particular probabilities of
# finalization by our algorithm are actually finalized
def calibrate(finalized_hashes):
thresholds = range(-10, 11)
signed = [0] * (len(thresholds) - 1)
_finalized = [0] * (len(thresholds) - 1)
_discarded = [0] * (len(thresholds) - 1)
for s in all_signatures:
for i, prob in enumerate(s.probs):
if i + s.sign_from >= len(finalized_hashes):
continue
actual_result = 1 if finalized_hashes[i + s.sign_from] else 0
index = 0
while index + 2 < len(thresholds) and prob > thresholds[index + 1]:
index += 1
signed[index] += 1
if actual_result == 1:
_finalized[index] += 1
elif actual_result == 0:
_discarded[index] += 1
for i in range(len(thresholds) - 1):
if _finalized[i] + _discarded[i]:
print 'Probability from %f to %f: %f (%d of %d)' % (thresholds[i], thresholds[i+1], _finalized[i] * 1.0 / (_finalized[i] + _discarded[i]), _finalized[i], _finalized[i] + _discarded[i])
print 'Percentage of block heights filled: %f%%' % (len([x for x in finalized_hashes if x]) * 100.0 / len(finalized_hashes))
def run(steps=4000):
n = networksim.NetworkSimulator()
for i in range(NUM_VALIDATORS):
n.agents.append(Validator(i, n))
n.generate_peers(3)
while len(all_signatures):
all_signatures.pop()
for x in future.keys():
del future[x]
for x in finalized_blocks.keys():
del finalized_blocks[x]
for x in discarded.keys():
del discarded[x]
for i in range(steps):
n.tick()
if i % 500 == 0:
minmax = 99999999999999999
for x in n.agents:
minmax = min(minmax, x.max_finalized_height - 10)
print get_opinions(n)[max(minmax, 0):]
finalized0 = [(v.max_finalized_height, v.finalized_hashes) for v in n.agents]
if CHECK_INTEGRITY:
finalized = sorted(finalized0, key=lambda x: len(x[1]))
for j in range(len(n.agents) - 1):
for k in range(len(finalized[j][1])):
if finalized[j][1][k] is not None and finalized[j+1][1][k] is not None:
if finalized[j][1][k] != finalized[j+1][1][k]:
print finalized[j]
print finalized[j+1]
raise Exception("Finalization mismatch: %r %r" % (finalized[j][1][k], finalized[j+1][1][k]))
print 'Finalized status: %r' % [x[0] for x in finalized0]
_all = finalized0[0][1]
_pos = len([x for x in _all if x])
_neg = len([x for x in _all if not x])
print 'Finalized blocks: %r (%r positive, %r negaitve)' % (len(_all), _pos, _neg)
if i == 10000 and NETSPLITS >= 1:
print "###########################################################"
print "Knocking off 20% of the network!!!!!"
print "###########################################################"
n.knock_offline_random(NUM_VALIDATORS // 5)
if i == 20000 and NETSPLITS >= 2:
print "###########################################################"
print "Simluating a netsplit!!!!!"
print "###########################################################"
n.generate_peers()
n.partition()
if i == 30000 and NETSPLITS >= 1:
print "###########################################################"
print "Network health back to normal!"
print "###########################################################"
n.generate_peers()
calibrate(n.agents[0].finalized_hashes[:n.agents[0].max_finalized_height + 1])