class Server(object):
_sync = {'is_alive':'1', 'prepare':'2', 'get_accepted_values':'2'}
_async = ['set_multi', 'set_interval','promise', 'set_proposal', 'onPrepare',
'accepted', 'accept', 'set_leader', 'heartbeat' ]
_ref = ['set_multi', 'onPrepare', 'accept', 'accepted', 'set_proposal']
_parallel = ['heartbeat']
def __init__(self, quorum_size):
self.quorum_size = quorum_size
self.retries = 0
self.last_log_index = None
self.min_proposal = None
self.first_unchosen_index = 0
self.accepted_value = {}
self.accepted_proposal = {}
self.index = 0
self.max_round = 0
self.leader = False
self.highestInstance = 0
self.prepared = False
self.next_index = self.index + 1
self.leader_proxy = None
self.proposed_value = {}
self.last_accepted_id = {}
self.next_proposal_number = 1 # [1]*self.max_round
self.num_noMoreAccepted = {}
self.accepted_rcvd = set()
self.server_dict = {}
def set_leader(self):
self.leader = True
def set_server_dict(self):
'''Dict <key, value> --> <server_id, server_reference>'''
for acceptor in self.list_acceptors:
self.server_dict[acceptor.get_id()] = acceptor
def set_multi(self, list_acceptors):
self.list_acceptors = list_acceptors
self.set_server_dict()
self.amulti = AMulti(self.list_acceptors)
self.smulti = SMulti(self.proxy, self.list_acceptors)
def get_accepted_values(self):
return self.accepted_value.values()
'''Leader Election'''
def heartbeat(self):
change_leader = True
list_ids = self.smulti.is_alive()
max_id = max(list_ids.values())
if max_id > self.id:
change_leader = False
self.leader_proxy = self.server_dict[max_id]
if change_leader:
self.retries +=1
else:
self.retries = 0
if self.retries >= 2:
self.leader = True
def is_alive(self):
return self.id
def set_proposal(self, value, client):
'''
Sets the proposal value for this node if this node is not the leader, it redirect the value
to actual leader.
'''
self.current_client = client
if not self.leader:
if not self.leader_proxy:
return False
return self.leader_proxy.set_proposal(value, client)
else:
self.index = self.highestInstance
self.proposed_value[self.index]= value
self.highestInstance += 1
self.last_accepted_id[self.index] = 0
self.num_noMoreAccepted[self.index] = 0
self.prepare()
'''
Acceptor
'''
def onPrepare(self, proposer, n, index):
'''
Called when a Prepare message is received from a Proposer
'''
if n >= self.min_proposal:
# Duplicate prepare message
self.min_proposal = n
try:
proposer.promise(self.id, self.accepted_proposal[index], self.accepted_value[index], True)
except:
proposer.promise(self.id, None, None, True)
def accept(self, proxy, index, n, v, first_unchosen_index):
'''
Called when an Accept! message is received from a Proposer
'''
if n >= self.min_proposal:
self.accepted_proposal[index] = n
self.min_proposal = n
self.accepted_value[index] = v
'''send accepted to all learners!! '''
# self.amulti.accepted(self.id, proposal_id, self.accepted_value)
for i in range(1, first_unchosen_index-1):
if self.accepted_proposal[i] == n:
self.accepted_proposal[i] = 0
'''revisar returns'''
# print proxy, proxy.get_id()
proxy.accepted(self.proxy, self.min_proposal, self.first_unchosen_index)
# '''send accepted to all learners!! '''
# self.amulti.accepted(self.id, proposal_id, self.accepted_value)
def success(self, index, v):
self.accepted_value[index] = v
self.accepted_proposal[index] = 0
'''revisar returns'''
return self.firstUnchosenIndex
'''
Proposer
'''
def prepare(self):
'''
Sends a prepare request to all Acceptors as the first step in attempting to
acquire leadership of the Paxos instance.
'''
if self.prepared:
try:
self.accepted_rcvd = set()
self.amulti.accept(self.proxy, self.index, self.min_proposal, self.proposed_value[self.index], self.first_unchosen_index)
except:
return False
else:
self.promises_rcvd = set()
self.min_proposal = ProposalID(self.next_proposal_number, self.id)
self.next_proposal_number += 1
#multi to all acceptors!!
self.amulti.onPrepare(self.proxy, self.min_proposal, self.index)
return True
def promise(self, from_uid, accepted_proposal, accepted_value, noMoreAccepted):
#if accepted_proposal
#si el maxim accepted_proposal != 0
'''
Called when a Promise message is received from an Acceptor
'''
# Ignore the message if it's for an old proposal or we have already received
# a response from this Acceptor
#if accepted_proposal != self.accepted_proposal[self.index] or from_uid in self.promises_rcvd:
# return None
self.promises_rcvd.add( from_uid )
#si el maxim accepted_proposal != 0
print 'last_accepted_id', self.last_accepted_id, 'index', self.index
if accepted_proposal > self.last_accepted_id[self.index]:
self.last_accepted_id[self.index] = accepted_proposal
# If the Acceptor has already accepted a value, we MUST set our proposal
# to that value.
if accepted_value is not None:
self.proposed_value[self.index] = accepted_value
if noMoreAccepted:
self.num_noMoreAccepted[self.index] += 1
if len(self.promises_rcvd) > self.quorum_size/2:
if self.num_noMoreAccepted[self.index] > self.quorum_size/2:
self.prepared = True
if self.proposed_value[self.index] is not None:
self.accepted_rcvd = set()
self.amulti.accept(self.proxy, self.index, self.min_proposal, self.proposed_value[self.index], self.first_unchosen_index)
self.promises_rcvd = set()
def accepted(self, proxy, n, first_unchosen_index):
self.accepted_rcvd.add( proxy.get_id())
if n > self.min_proposal:
self.max_round = n
self.prepared = False
# self.prepare()
if first_unchosen_index <= self.last_log_index and self.accepted_proposal[first_unchosen_index] == 0:
result = proxy.success(first_unchosen_index, self.accepted_value[first_unchosen_index])
self.index = result
while True:
if (result < self.first_unchosen_index):
result = proxy.success(result, self.accepted_value[result])
self.index = result
else:
break
if len(self.accepted_rcvd) > self.quorum_size/2:
self.accepted_proposal[self.index] = 0
self.accepted_value[self.index] = self.proposed_value[self.index]
self.current_client.internal_get(self.accepted_value[self.index])
