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Commit cb3e6a9f authored by Dixon Tirtayadi's avatar Dixon Tirtayadi
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Mencius is working when a majority of server is alive

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project/__pycache__/message.cpython-39.pyc
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project/__pycache__/timers.cpython-39.pyc
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project/mencius.py
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......@@ -34,7 +34,7 @@ class Paxos(socketserver.UDPServer):
self.slot_to_acceptors: DefaultDict[int, Set[Address]] = defaultdict(set) # Used by leader to decide majority for each slot after P2B, Multimap<Integer, Address>
# for leader election
self.voters: Set[Address] = set() # Yes votes for leader election, set of addresses
self.voters: List[Set[Address]] = [set()] * self.n_server # Yes votes for leader election, set of addresses
self.p1b_replies: Dict[int, BallotValuePair] = dict() # Accepted values for each slot by acceptors that voted yes, slot number -> proposal
# lock manager app
......@@ -47,6 +47,7 @@ class Paxos(socketserver.UDPServer):
self.is_leader[i] = True
# Change starting slot
self.slot_in = i
self.leader_recent_ping[i] = True
self.highest_ballot_seen.append(BallotNumber(1, self.servers[i]))
print("Finished init paxos", file=sys.stdout)
......@@ -58,7 +59,7 @@ class Paxos(socketserver.UDPServer):
socketserver.UDPServer.__init__(self, address, PaxosHandler)
setTimer(HeartBeatTimer(), HeartBeatTimer.HEARTBEAT_RETRY_MILLIS, self.onHeartBeatTimer)
setTimer(HeartBeatCheckTimer(self.highest_ballot_seen), HeartBeatTimer.HEARTBEAT_RETRY_MILLIS, self.onHeartBeatCheckTimer)
setTimer(HeartBeatCheckTimer(self.highest_ballot_seen), HeartBeatCheckTimer.HEARTBEAT_CHECK_RETRY_MILLIS, self.onHeartBeatCheckTimer)
def handlePaxosRequest(self, paxos_req, sender):
# print(f"{self.address} Got Paxos Request from {sender}", file=sys.stdout)
......@@ -100,26 +101,35 @@ class Paxos(socketserver.UDPServer):
self.executeLog("handlePaxosRequest")
def handleP1A(self, p1a, sender):
if self.highest_ballot_seen < p1a.ballot_num:
self.highest_ballot_seen = p1a.ballot_num
leader_slot = p1a.leader_slot
if self.highest_ballot_seen[leader_slot] < p1a.ballot_num:
self.highest_ballot_seen[leader_slot] = p1a.ballot_num
# Update the ballot for other highest ballot seen from the same address
for i in range(self.n_server):
if p1a.ballot_num.addr == self.highest_ballot_seen[i].addr:
if p1a.ballot_num.seq_num > self.highest_ballot_seen[i].seq_num:
self.highest_ballot_seen[i] = p1a.ballot_num
# If we are leader, make this a follower (since the one sending P1A thinks they are leader)
if self.is_leader:
print(f"{self.address} demotes itself from leader")
self.is_leader = False
if self.is_leader[leader_slot]:
print(f"{self.address} demotes itself from leader from slot {leader_slot}")
self.is_leader[leader_slot] = False
p1b = P1B(self.address, self.highest_ballot_seen, self.accepted)
p1b = P1B(self.address, self.highest_ballot_seen[leader_slot], self.accepted, leader_slot)
self.send_msg(p1b, sender)
setTimer(HeartBeatCheckTimer(p1a.ballot_num), HeartBeatCheckTimer.HEARTBEAT_CHECK_RETRY_MILLIS * 2, self.onHeartBeatCheckTimer)
self.leader_recent_ping = True
setTimer(HeartBeatCheckTimer(self.highest_ballot_seen), HeartBeatCheckTimer.HEARTBEAT_CHECK_RETRY_MILLIS * 2, self.onHeartBeatCheckTimer)
self.leader_recent_ping[leader_slot] = True
def handleP1B(self, p1b, sender):
if self.is_leader:
leader_slot = p1b.leader_slot
if self.is_leader[leader_slot]:
return
# If receive majority of response from acceptors with its ballot, becomes leader
if self.ballot == p1b.accepted_ballot and self.ballot == self.highest_ballot_seen:
self.voters.update(sender)
if self.ballot == p1b.accepted_ballot and self.ballot == self.highest_ballot_seen[leader_slot]:
self.voters[leader_slot].update(sender)
for slot in p1b.accepted:
new_bvp = p1b.accepted[slot]
if slot not in self.p1b_replies:
......@@ -128,11 +138,11 @@ class Paxos(socketserver.UDPServer):
cur_bvp = self.p1b_replies[slot]
if new_bvp.ballot_num >= cur_bvp.ballot_num:
self.p1b_replies[slot] = new_bvp
if len(self.voters) > (len(self.servers) / 2 - 1):
if len([self.voters[leader_slot]]) > (len(self.servers) / 2 - 1):
# This server is elected as leader
if not self.is_leader:
print(f"{self.address} becomes leader")
self.is_leader = True
if not self.is_leader[leader_slot]:
print(f"{self.address} becomes leader for slot {leader_slot}")
self.is_leader[leader_slot] = True
# Must update its state with accepted values from acceptors
for slot in self.p1b_replies:
value = self.p1b_replies[slot]
......@@ -141,13 +151,14 @@ class Paxos(socketserver.UDPServer):
# self.slot_in = max(self.slot_in, slot + 1)
# Changed: Instead of doing max of slot_in, do while loop:
while self.slot_in <= slot:
# Propose no-op(SKIP message) and send it straight away for the slot we skip
skip = P2A(self.address, BallotNumber(self.ballot.seq_num, self.address), self.slot_in, None)
for acceptor in self.servers:
if acceptor != self.address:
self.send_msg(skip, acceptor)
bvp = BallotValuePair(BallotNumber(self.ballot.seq_num, self.address), None)
self.log[self.slot_in] = bvp
# This chunk of code is not needed, we just need to increment slot_in, executeLog will be the one taking care of proposing SKIP
# # Propose no-op(SKIP message) and send it straight away for the slot we skip
# skip = P2A(self.address, BallotNumber(self.ballot.seq_num, self.address), self.slot_in, None)
# for acceptor in self.servers:
# if acceptor != self.address:
# self.send_msg(skip, acceptor)
# bvp = BallotValuePair(BallotNumber(self.ballot.seq_num, self.address), None)
# self.log[self.slot_in] = bvp
self.incrementSlotIn()
bvp = self.proposals[slot]
......@@ -181,6 +192,9 @@ class Paxos(socketserver.UDPServer):
# Learn it immediately if value is None and proposed by the leader
bvp = BallotValuePair(BallotNumber(p2a.ballot_num.seq_num, p2a.addr), None)
self.log[p2a.slot_num] = bvp
self.slot_to_acceptors[p2a.slot_num].add(self.address)
self.proposals[p2a.slot_num] = bvp
self.accepted[p2a.slot_num] = bvp
print(f"Learned skip for {p2a}")
return
......@@ -215,7 +229,8 @@ class Paxos(socketserver.UDPServer):
# print("p2a - 3\n")
def handleP2B(self, p2b, sender):
if not self.is_leader:
slot = self.slotToLeaderIndex(p2b.slot_num)
if not self.is_leader[slot]:
# Not leader, drop message
return
......@@ -235,8 +250,10 @@ class Paxos(socketserver.UDPServer):
def handleLeaderHeartbeat(self, heartbeat, address):
for i in range(len(heartbeat.leader_slot)):
if not self.is_leader[i] and heartbeat.leader_slot[i]:
# print(f"{self.address} got heartbeat from {heartbeat.ballot_num} at index {i}")
if self.highest_ballot_seen[i] > heartbeat.ballot_num:
# It's not "leader" heartbeat
# print(f"{self.address} drops heartbeat from {heartbeat.ballot_num} at index {i} because of highest is {self.highest_ballot_seen[i]}")
return
newLeaderSeen = False
if self.highest_ballot_seen[i] < heartbeat.ballot_num:
......@@ -252,8 +269,8 @@ class Paxos(socketserver.UDPServer):
new_bvp = heartbeat.log[slot]
if new_bvp > bvp:
self.log[slot] = new_bvp
self.executeLog("Handle Leader Heartbeat")
# TODO: Uncomment below
# self.executeLog("Handle Leader Heartbeat")
self.leader_recent_ping[i] = True
if newLeaderSeen:
# Exponential backoff
......@@ -267,7 +284,8 @@ class Paxos(socketserver.UDPServer):
def onP2ATimer(self, p2a_timer: P2ATimer):
# print(f"{p2a_timer}: Callback", file=sys.stdout)
# If not leader then stop timer
if self.is_leader and not self.status(p2a_timer.p2a.slot_num) == PaxosLogSlotStatus.CHOSEN:
leader_slot = self.slotToLeaderIndex(p2a_timer.p2a.slot_num)
if self.is_leader[leader_slot] and not self.status(p2a_timer.p2a.slot_num) == PaxosLogSlotStatus.CHOSEN:
for acceptor_addr in self.servers:
if acceptor_addr != self.address:
self.send_msg(p2a_timer.p2a, acceptor_addr)
......@@ -287,8 +305,15 @@ class Paxos(socketserver.UDPServer):
# Change: Since everyone is leader, heartbeat is now being sent from all leader, we
# need to keep track which heartbeat is last heard, and if one leader is dead, we take
# over that leader slot.
# Drop if this is not the latest heartbeat check
if heartbeat_check_timer.ballot_num != self.highest_ballot_seen:
return
# print(f"{heartbeat_check_timer}: Callback", file=sys.stdout)
print(f"{heartbeat_check_timer}: Callback", file=sys.stdout)
print(f"{self.address}: Recent ping {self.leader_recent_ping}", file=sys.stdout)
print(f"{self.address}: Leader {self.is_leader}", file=sys.stdout)
print(f"{self.address}: Ballot {[str(i) for i in self.highest_ballot_seen]}", file=sys.stdout)
print("\n")
for i in range(len(heartbeat_check_timer.ballot_num)):
if not self.is_leader[i]:
if heartbeat_check_timer.ballot_num[i] == self.highest_ballot_seen[i]:
......@@ -298,34 +323,38 @@ class Paxos(socketserver.UDPServer):
# Just for randomization for contention issue
# TODO: Uncomment below for the electing leader, will need to add index
# to know which slot are we trying to become the leader of.
# self.__electLeader()
self.__electLeader(i)
return
self.leader_recent_ping[i] = False
setTimer(heartbeat_check_timer, HeartBeatCheckTimer.HEARTBEAT_CHECK_RETRY_MILLIS, self.onHeartBeatCheckTimer)
setTimer(heartbeat_check_timer, HeartBeatCheckTimer.HEARTBEAT_CHECK_RETRY_MILLIS, self.onHeartBeatCheckTimer)
def onLeaderElectionTimer(self, leader_election_timer: LeaderElectionTimer):
# print(f"{leader_election_timer}: Callback", file=sys.stdout)
if self.highest_ballot_seen == self.ballot and not self.is_leader:
leader_slot = leader_election_timer.p1a.leader_slot
if self.highest_ballot_seen[leader_slot] == self.ballot and not self.is_leader[leader_slot]:
for acceptor_addr in self.servers:
if acceptor_addr != self.address:
self.send_msg(leader_election_timer.p1a, acceptor_addr)
setTimer(leader_election_timer, LeaderElectionTimer.LEADER_ELECTION_TIMER, self.onLeaderElectionTimer)
def __electLeader(self):
print(f"{self.address} Detected leader is dead, try to get ourself to become leader")
def __electLeader(self, leader_slot):
print(f"{self.address} Detected leader {leader_slot} is dead, try to get ourself to become leader")
# Try to elect ourself as the leader
# Try to get elected as leader at the beginning of time
self.voters.clear()
self.voters[leader_slot].clear()
self.p1b_replies.clear()
self.p1b_replies.update(self.accepted)
# Increase ballot until higher than the highest we saw before electing
while self.ballot < self.highest_ballot_seen:
while self.ballot < self.highest_ballot_seen[leader_slot]:
self.ballot.increaseBallot()
p1a: P1A = P1A(self.address, BallotNumber(self.ballot.seq_num, self.address))
self.highest_ballot_seen = p1a.ballot_num
for i in range(self.n_server):
if self.is_leader[i]:
self.highest_ballot_seen[i] = self.ballot
p1a: P1A = P1A(self.address, BallotNumber(self.ballot.seq_num, self.address), leader_slot)
self.highest_ballot_seen[leader_slot] = p1a.ballot_num
# P1A
for acceptor_addr in self.servers:
......@@ -366,9 +395,12 @@ class Paxos(socketserver.UDPServer):
for tmp_server in self.servers:
if tmp_server != self.address:
self.send_msg(p2a, tmp_server)
bvp = BallotValuePair(BallotNumber(self.ballot.seq_num, self.address), None)
self.log[self.slot_in] = bvp
self.slot_to_acceptors[j].add(self.address)
self.proposals[j] = BallotValuePair(BallotNumber(self.ballot.seq_num, self.address), p2a.value)
self.accepted[j] = BallotValuePair(BallotNumber(self.ballot.seq_num, self.address), p2a.value)
self.proposals[j] = bvp
self.accepted[j] = bvp
def slotToLeaderIndex(self, slot) -> int:
return slot % self.n_server
......
project/message.py
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View file @ cb3e6a9f
......@@ -12,7 +12,7 @@ class Message:
class LeaderHeartbeat(Message):
def __init__(self, addr: Address, log: Dict[int, BallotValuePair], ballot_num: BallotNumber, leader_slot: int) -> None:
def __init__(self, addr: Address, log: Dict[int, BallotValuePair], ballot_num: BallotNumber, leader_slot: List[bool]) -> None:
super().__init__(addr)
self.log: Dict[int, BallotValuePair] = log
self.ballot_num: BallotNumber = ballot_num
......
project/timers.py
+ 1
− 1
View file @ cb3e6a9f
......@@ -43,7 +43,7 @@ class HeartBeatTimer(Timer):
class HeartBeatCheckTimer(Timer):
HEARTBEAT_CHECK_RETRY_MILLIS = 10000000000
HEARTBEAT_CHECK_RETRY_MILLIS = 5000
def __init__(self, ballot_num: List[BallotNumber]) -> None:
super().__init__()
......
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