def server(server_id, config_file='../config/servers.yaml'):
server_id = int(server_id)
#load config file
with open(config_file, 'r') as config_handler:
config = yaml.load(config_handler)
f = int(config['f']) #the number of failure that can be tolerated
state_backup_folder = config['state_backup_folder']
if not os.path.exists(state_backup_folder):
call(['mkdir', '-p', state_backup_folder])
num_server = 2 * f + 1
servers_list = {
server_idx: config['servers_list'][server_idx]
for server_idx in range(num_server)
}
quorum = num_server / 2 + 1
# load state
state_backup = get_state_backup(server_id, state_backup_folder)
if not os.path.exists(state_backup):
state = dict(view=0,
decided_log={},
promised_proposal_id=None,
accepted_proposal_id={},
accepted_proposal_val={},
accepted_client_info={})
save_state(state_backup, state)
else:
MyLogging.info("Recovering server")
state = load_state(state_backup)
loss_rate = config['msg_drop_rate']
proposer = Proposer(server_id, servers_list, loss_rate)
acceptor = Acceptor(server_id, servers_list, state['promised_proposal_id'],
state['accepted_proposal_id'],
state['accepted_proposal_val'],
state['accepted_client_info'], state_backup, loss_rate)
learner = Learner(server_id, quorum, state['decided_log'], state_backup,
loss_rate)
#initialize view. The view will be used for proposal_id for elected leader
view = state['view']
num_acceptors = num_server
HOST = servers_list[server_id]['host']
PORT = servers_list[server_id]['port']
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(100)
#for test case 4 to skip slot x
if 'x' in config and config['x'] >= 0:
x = int(config['x'])
else:
x = None
if 'num_failed_primary' in config and config['num_failed_primary'] >= 0:
num_failed_primary = int(config['num_failed_primary'])
else:
num_failed_primary = None
#for test 4 to specify the server on which the skipped slot occurs
server_skip = 0
request_val_queue = collections.deque()
client_info_queue = collections.deque()
while True:
#try to crash
if view % num_acceptors == server_id:
server_crash(server_id, crash_rate)
MyLogging.debug("wait for connection")
conn, addr = s.accept()
MyLogging.debug('Connection by ' + str(addr))
data = conn.recv(4096 * 2)
msg = pickle.loads(data)
MyLogging.debug('RCVD: ' + str(msg))
if msg['type'] == 'request':
if msg['resend_idx'] != 0:
#if this is an resent message, triger view change
# save updated state first
state = load_state(state_backup)
state['view'] = view + 1
save_state(state_backup, state)
view += 1
#new leader clears the request queue
request_val_queue.clear()
client_info_queue.clear()
proposer.need_prepare = True
MyLogging.debug("change to view %s" % (str(view)))
if view % num_acceptors == server_id:
#this is leader
#testcase 2 and 3
if num_failed_primary is not None and server_id < num_failed_primary:
MyLogging.info("force the primary %s to crash" %
(str(server_id)))
MyLogging.error("server id %s crashes" % (str(server_id)))
exit()
#testcase 4
if x is not None and x + 1 in learner.decided_log and server_skip == server_id:
#server_skip = server_id
MyLogging.info('server id %s has learned slot %s' %
(str(server_id), str(x + 1)))
MyLogging.error("server id %s crashes" % (str(server_id)))
exit()
request_val_queue.append(msg['request_val'])
client_info_queue.append(msg['client_info'])
if proposer.need_prepare is True:
proposer.prepare(view)
else: #directly propose without prepare stage
proposal_pack = {}
MyLogging.debug("no need to prepare")
MyLogging.debug(request_val_queue)
for _ in range(len(request_val_queue)):
request_val = request_val_queue.popleft()
client_info = client_info_queue.popleft()
proposal_pack = proposer.addNewRequest(
proposal_pack, request_val, client_info)
#testcase 4
if x is not None and x in proposal_pack and server_skip == server_id:
MyLogging.debug('At slot %s: %s' %
(str(x), str(proposal_pack[x])))
MyLogging.debug(
'proposer %s skips slot %s for server_skip %s' %
(str(server_id), str(x), str(server_skip)))
del proposal_pack[x]
proposer.propose(proposal_pack, without_prepare=True)
elif msg['type'] == 'promise':
proposer.addVote(msg)
if proposer.checkQuorumSatisfied() is True:
if proposer.need_prepare is True:
proposal_pack = proposer.getProposalPack(
learner.getDecidedLog())
MyLogging.debug("proposal pack for holes: %s" %
(str(proposal_pack)))
for _ in range(len(request_val_queue)):
request_val = request_val_queue.popleft()
client_info = client_info_queue.popleft()
proposal_pack = proposer.addNewRequest(
proposal_pack, request_val, client_info)
#testcase 4
if x is not None and x in proposal_pack and server_skip == server_id:
MyLogging.debug('At slot %s: %s' %
(str(x), str(proposal_pack[x])))
MyLogging.debug(
'proposer %s skips slot %s for server_skip %s' %
(str(server_id), str(x), str(server_skip)))
del proposal_pack[x]
proposer.propose(proposal_pack)
proposer.need_prepare = False
elif msg['type'] == 'prepare':
# save updated state first
state = load_state(state_backup)
state['view'] = max(view, msg['proposal_id'])
save_state(state_backup, state)
view = max(view, msg['proposal_id']
) # try to catch up with the most recent view
MyLogging.debug("change to max view %s" % (str(view)))
acceptor.promise(msg)
elif msg['type'] == 'propose':
acceptor.accept(msg)
elif msg['type'] == 'accept':
slot_idx = msg['slot_idx']
learner.addVote(msg, slot_idx)
if learner.checkQuorumSatisfied(slot_idx) is True:
learner.decide(slot_idx)
conn.close()
