def twophase(db):
state = 'waiting'
hnum = 0
nreceives = 0
client = None
request_q = deque()
while True:
if len(request_q) > 0 and state == 'waiting':
data, sock, addr = request_q.popleft()
else:
data, sock, addr = (yield)
if 'request' in data:
if state != 'waiting':
request_q.append((data, sock, addr))
continue
# we have been chosen as the coordinator
# we need to check with all acceptors
print 'coordinator received request, preparing %s' % str(data)
client = addr
state = 'preparing'
nreceives = 0
prep_msg = json.dumps({
'protocol': '2pc',
'prepare': data['request'],
'i': hnum + 1
})
bcast(sock, prep_msg)
elif state == 'preparing':
if 'promise' in data:
nreceives += 1
if nreceives == len(servers):
print 'got n promises, moving on'
state = 'accepting'
nreceives = 0
accept_msg = json.dumps({
'protocol': '2pc',
'accept': data['promise'],
'i': hnum
})
bcast(sock, accept_msg)
elif 'nack' in data:
state = 'waiting'
nreceives = 0
elif state == 'accepting':
if 'accepted' in data:
nreceives += 1
if nreceives == len(servers):
print 'successfully got n accepts'
success_msg = json.dumps({
'protocol': '2pc',
'success': True
})
sock.sendto(success_msg, client)
state = 'waiting'
nreceives = 0
client = None
elif 'nack' in data:
state = 'waiting'
nreceives = 0
if 'prepare' in data:
if data['i'] > hnum:
hnum = data['i']
response = json.dumps({
'protocol': '2pc',
'promise': data['prepare'],
'i': data['i']
})
else:
response = json.dumps({'protocol': '2pc', 'nack': data['i']})
sock.sendto(response, addr)
elif 'accept' in data:
if data['i'] == hnum:
learner.send(data['accept'])
response = json.dumps({
'protocol': '2pc',
'accepted': data['accept'],
'i': hnum
})
else:
response = json.dumps({'protocol': '2pc', 'nack': data['i']})
sock.sendto(response, addr)
def twophase(db):
state = 'waiting'
hnum = 0
nreceives = 0
client = None
request_q = deque()
while True:
if len(request_q) > 0 and state == 'waiting':
data, sock, addr = request_q.popleft()
else:
data, sock, addr = (yield)
if 'request' in data:
if state != 'waiting':
request_q.append((data, sock, addr))
continue
# we have been chosen as the coordinator
# we need to check with all acceptors
print 'coordinator received request, preparing %s' % str(data)
client = addr
state = 'preparing'
nreceives = 0
prep_msg = json.dumps({'protocol':'2pc',
'prepare':data['request'],
'i':hnum + 1})
bcast(sock, prep_msg)
elif state == 'preparing':
if 'promise' in data:
nreceives += 1
if nreceives == len(servers):
print 'got n promises, moving on'
state = 'accepting'
nreceives = 0
accept_msg = json.dumps({'protocol':'2pc',
'accept':data['promise'],
'i':hnum})
bcast(sock, accept_msg)
elif 'nack' in data:
state = 'waiting'
nreceives = 0
elif state == 'accepting':
if 'accepted' in data:
nreceives += 1
if nreceives == len(servers):
print 'successfully got n accepts'
success_msg = json.dumps({'protocol':'2pc',
'success':True})
sock.sendto(success_msg, client)
state = 'waiting'
nreceives = 0
client = None
elif 'nack' in data:
state = 'waiting'
nreceives = 0
if 'prepare' in data:
if data['i'] > hnum:
hnum = data['i']
response = json.dumps({'protocol':'2pc',
'promise':data['prepare'],
'i':data['i']})
else:
response = json.dumps({'protocol':'2pc',
'nack':data['i']})
sock.sendto(response, addr)
elif 'accept' in data:
if data['i'] == hnum:
learner.send(data['accept'])
response = json.dumps({'protocol':'2pc',
'accepted':data['accept'],
'i':hnum})
else:
response = json.dumps({'protocol':'2pc',
'nack':data['i']})
sock.sendto(response, addr)
def paxos(learner):
state = 'waiting'
hnum = 0
nreceives = 0
client = None
request_q = deque()
current_i = None
while True:
if len(request_q) > 0 and state == 'waiting':
# adds fifo semantics to system
data, sock, addr = request_q.popleft()
else:
data, sock, addr = (yield)
if 'request' in data:
if state != 'waiting':
request_q.append((data, sock, addr))
log_warn('queue contains %s elements' % len(request_q))
continue
# we have been chosen as the proposer
# we need to check with all acceptors
log_verbose('coordinator received request, preparing %s' %
str(data))
client = addr
state = 'preparing'
nreceives = 0
current_i = hnum + 1
prep_msg = json.dumps({
'protocol': 'paxos',
'prepare': data['request'],
'i': hnum + 1
})
bcast(sock, prep_msg)
elif state == 'preparing':
if 'promise' in data and data['i'] == current_i:
nreceives += 1
if nreceives > (len(servers) / 2):
log_verbose('got more than n/2 promises, moving on')
state = 'accepting'
nreceives = 0
accept_msg = json.dumps({
'protocol': 'paxos',
'accept': data['promise'],
'i': hnum
})
bcast(sock, accept_msg)
elif 'nack' in data and data['i'] != current_i:
log_warn('caught (and ignored) old nack: %s\tcurrent i: %s' %
(data['i'], current_i))
elif 'nack' in data and data['i'] == current_i:
log_warn('falling back to waiting state from preparing')
log_fail('nack id: %s\thnum: %s' % (data['i'], hnum))
state = 'waiting'
nreceives = 0
elif state == 'accepting':
if 'accepted' in data and data['i'] == current_i:
nreceives += 1
if nreceives > (len(servers) / 2):
log_verbose('successfully got more than n/2 accepts')
success_msg = json.dumps({
'protocol': 'paxos',
'success': True
})
sock.sendto(success_msg, client)
state = 'waiting'
nreceives = 0
current_i = None
client = None
elif 'nack' in data and data['i'] != current_i:
log_warn('caught (and ignored) old nack: %s\tcurrent i: %s' %
(data['i'], current_i))
elif 'nack' in data and data['i'] == current_i:
log_warn('falling back to waiting state from accepting')
log_fail('possible inconsistency')
log_fail('nack id: %s\thnum: %s' % (data['i'], hnum))
state = 'waiting'
nreceives = 0
if 'prepare' in data:
if data['i'] > hnum:
hnum = data['i']
response = json.dumps({
'protocol': 'paxos',
'promise': data['prepare'],
'i': data['i']
})
else:
log_warn('got prepare for number less than hnum')
response = json.dumps({'protocol': 'paxos', 'nack': data['i']})
sock.sendto(response, addr)
elif 'accept' in data:
if data['i'] == hnum:
learner.send(data['accept'])
response = json.dumps({
'protocol': 'paxos',
'accepted': data['accept'],
'i': hnum
})
else:
log_warn('got accept for number other than hnum')
log_fail('possible inconsistency')
response = json.dumps({'protocol': 'paxos', 'nack': data['i']})
sock.sendto(response, addr)
def paxos(learner):
state = "waiting"
hnum = 0
nreceives = 0
client = None
request_q = deque()
current_i = None
while True:
if len(request_q) > 0 and state == "waiting":
# adds fifo semantics to system
data, sock, addr = request_q.popleft()
else:
data, sock, addr = (yield)
if "request" in data:
if state != "waiting":
request_q.append((data, sock, addr))
log_warn("queue contains %s elements" % len(request_q))
continue
# we have been chosen as the proposer
# we need to check with all acceptors
log_verbose("coordinator received request, preparing %s" % str(data))
client = addr
state = "preparing"
nreceives = 0
current_i = hnum + 1
prep_msg = json.dumps({"protocol": "paxos", "prepare": data["request"], "i": hnum + 1})
bcast(sock, prep_msg)
elif state == "preparing":
if "promise" in data and data["i"] == current_i:
nreceives += 1
if nreceives > (len(servers) / 2):
log_verbose("got more than n/2 promises, moving on")
state = "accepting"
nreceives = 0
accept_msg = json.dumps({"protocol": "paxos", "accept": data["promise"], "i": hnum})
bcast(sock, accept_msg)
elif "nack" in data and data["i"] != current_i:
log_warn("caught (and ignored) old nack: %s\tcurrent i: %s" % (data["i"], current_i))
elif "nack" in data and data["i"] == current_i:
log_warn("falling back to waiting state from preparing")
log_fail("nack id: %s\thnum: %s" % (data["i"], hnum))
state = "waiting"
nreceives = 0
elif state == "accepting":
if "accepted" in data and data["i"] == current_i:
nreceives += 1
if nreceives > (len(servers) / 2):
log_verbose("successfully got more than n/2 accepts")
success_msg = json.dumps({"protocol": "paxos", "success": True})
sock.sendto(success_msg, client)
state = "waiting"
nreceives = 0
current_i = None
client = None
elif "nack" in data and data["i"] != current_i:
log_warn("caught (and ignored) old nack: %s\tcurrent i: %s" % (data["i"], current_i))
elif "nack" in data and data["i"] == current_i:
log_warn("falling back to waiting state from accepting")
log_fail("possible inconsistency")
log_fail("nack id: %s\thnum: %s" % (data["i"], hnum))
state = "waiting"
nreceives = 0
if "prepare" in data:
if data["i"] > hnum:
hnum = data["i"]
response = json.dumps({"protocol": "paxos", "promise": data["prepare"], "i": data["i"]})
else:
log_warn("got prepare for number less than hnum")
response = json.dumps({"protocol": "paxos", "nack": data["i"]})
sock.sendto(response, addr)
elif "accept" in data:
if data["i"] == hnum:
learner.send(data["accept"])
response = json.dumps({"protocol": "paxos", "accepted": data["accept"], "i": hnum})
else:
log_warn("got accept for number other than hnum")
log_fail("possible inconsistency")
response = json.dumps({"protocol": "paxos", "nack": data["i"]})
sock.sendto(response, addr)
