def __init__(self, host, port, log, peers, min_timeout=200, max_timeout=300, now_fun=datetime.utcnow):
self.now = now_fun
self.candidate_id = "%s:%d" % (host, port)
self.peers = peers
self.log = log
self.hosts = []
self.min_timeout = min_timeout
self.max_timeout = max_timeout
# Persistent State
self.current_term = 0
self.voted_for = None
# Volatile state
self.commit_index = None
self.last_applied = None
# Leader state
self.next_indexes = {}
self.match_indexes = {}
# Other state
self.current_term_end = None
self.reset_term_end()
self.role = StateMachine(FOLLOWER, LEADER, CANDIDATE)
self.roll.set_state(FOLLOWER)
self.leader_id = None
class RaftServer(FollowerMixin, CandidateMixin, LeaderMixin):
def __init__(self, host, port, log, peers, min_timeout=200, max_timeout=300, now_fun=datetime.utcnow):
self.now = now_fun
self.candidate_id = "%s:%d" % (host, port)
self.peers = peers
self.log = log
self.hosts = []
self.min_timeout = min_timeout
self.max_timeout = max_timeout
# Persistent State
self.current_term = 0
self.voted_for = None
# Volatile state
self.commit_index = None
self.last_applied = None
# Leader state
self.next_indexes = {}
self.match_indexes = {}
# Other state
self.current_term_end = None
self.reset_term_end()
self.role = StateMachine(FOLLOWER, LEADER, CANDIDATE)
self.roll.set_state(FOLLOWER)
self.leader_id = None
def start(self, loop):
loop.call_soon(self.election_coroutine)
loop.call_soon(self.election_timeout_coroutine)
loop.call_soon(self.leader_coroutine)
# -------------------------------------------------------------------------
#
# Incoming Request Coroutines
#
# -------------------------------------------------------------------------
def process_request_vote(self, msg):
term = msg["term"]
candidate_id = msg["candidate_id"]
last_log_index = msg["last_log_index"]
last_log_term = msg["last_log_term"]
result_fun = lambda res: dict(term=self.current_term, vote_granted=res)
# Term is too low, reject
if term < self.current_term:
return result_fun(False)
# Already chose a candidate, reject
if self.voted_for is not None and self.voted_for != candidate_id:
return result_fun(False)
# Log term is too old, reject
if last_log_term < self.log.term:
return result_fun(False)
# Not enough entries in the log, reject
if last_log_index < self.log.index:
return result_fun(False)
# Passed all the tests, allocate vote to candidate!
self.voted_for = candidate_id
return result_fun(True)
def process_append_entries(self, msg):
# Set the leader to be the leader_id from the sender
self.leader_id = msg["leader_id"]
# Leader/Candidate Reset after an election
if self.role.state != FOLLOWER and msg["term"] > self.current_term:
self.become_follower(msg["term"])
return self.log.append_entries(msg)
def process_message(self, msg):
action = msg.get("action")
if action == "append_entries":
return self.process_append_entries(msg)
elif action == "request_vote":
return self.process_request_vote(msg)
return dict(status="ERROR", msg="Unknown action type: {}".format(str(action)))
# -------------------------------------------------------------------------
#
# Helper Methods
#
# -------------------------------------------------------------------------
@property
def rand_timeout(self):
return random.randint(self.min_timeout, self.max_timeout)
def become_candidate(self):
self.role.set_state(CANDIDATE)
self.set_term(self.current_term + 1)
self.reset_term_end()
def become_follower(self, term):
self.role.set_state(FOLLOWER)
self.set_term(term)
self.reset_term_end()
def become_leader(self):
self.role.set_state(LEADER)
def reset_term_end(self):
now = self.now()
delta = timedelta(milliseconds=self.rand_timeout)
self.current_term_end = now + delta
def set_term(self, term):
if term > self.current_term:
self.current_term = term
self.voted_for = None
