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states.py
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states.py
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import asyncio
import logging
from random import randrange
import os
from utils import PersistentDict
from log import LogManager
from config import config
import statistics
logger = logging.getLogger(__name__)
class State:
def __init__(self, old_state=None, raft=None):
if old_state:
self.raft = old_state.raft
self.persist = old_state.persist
self.volatile = old_state.volatile
self.log = old_state.log
else:
self.raft = raft
self.persist = PersistentDict(os.path.join(config.storage, 'state'),
{'voteFor': None, 'currentTerm': 0})
self.volatile = {'laederId': None, 'cluster': config.cluster,
'address': config.address}
self.log = LogManager()
self._update_cluster()
def data_received_peer(self, peer, msg):
logger.info('Received %s from %s', msg['type'], peer)
if self.persist['currentTerm'] < msg['term'] and peer in self.volatile['cluster']:
self.persist['currentTerm'] = msg['term']
if not type(self) is Follower:
logging.info('Remote term is higher converting to Follower')
self.raft.change_state(Follower)
self.raft.state.data_received_peer(peer, msg)
return
method = getattr(self, 'on_peer_' + msg['type'], None)
if method:
method(peer, msg)
else:
logging.info(f'[heartbeat] Unrecognized message from {peer}: {msg}')
def data_received_client(self, protocol, msg):
method = getattr(self, 'on_client_' + msg['type'], None)
if method:
method(protocol, msg)
else:
logger.info("Unrecognized message from %s: %s",
protocol.transport.get_extra_info('peername'), msg)
def on_client_append(self, protocol, msg):
""" 指定client发送消息给leader """
msg = {'type': 'redirect',
'leader': self.volatile['leaderId'] if 'leaderId' in self.volatile.keys() else None}
protocol.send(msg)
logger.info("Redirect msg to %s, from: %s", self.volatile['leaderId'], self.volatile['address'])
def on_client_config(self, protocol, msg):
return self.on_client_append(protocol, msg)
def on_client_get(self, protocol, msg):
return self.on_client_append(protocol, msg)
def _update_cluster(self, entries=None):
""" Interface for updating config """
if 'cluster' in self.log.compacted.data:
self.volatile['cluster'] = self.log.compacted.data['cluster']
for entry in (self.log if entries is None else entries):
if entry['data']['key'] == 'cluster':
self.volatile['cluster'] = entry['data']['value']
self.volatile['cluster'] = tuple(map(tuple, self.volatile['cluster']))
class Follower(State):
def __init__(self, old_state=None, raft=None):
super().__init__(old_state, raft)
self.persist['voteFor'] = None
self.restart_election_timer()
def teardown(self):
self.election_timer.cancel()
def restart_election_timer(self):
if hasattr(self, 'election_timer'):
self.election_timer.cancel()
timeout = randrange(1, 4) * 10 ** 0
loop = asyncio.get_event_loop()
self.election_timer = loop.call_later(timeout, self.raft.change_state, Candidate)
logging.info(f"Election timer restarted: {timeout}")
def on_peer_request_vote(self, peer, msg):
term_is_current = msg['term'] >= self.persist['currentTerm']
can_vote = self.persist['voteFor'] in [tuple(msg['candidateId']), None]
index_is_current = (msg['lastLogTerm'] > self.log.term() or
(msg['lastLogTerm'] == self.log.term() and msg['lastLogIndex'] >= self.log.index))
granted = term_is_current and can_vote and index_is_current
if granted:
self.persist['voteFor'] = msg['candidateId']
self.restart_election_timer()
logging.info(f"Voting for {peer}. Term: {term_is_current}, vote: {can_vote}, index: {index_is_current}")
response = {
'type': 'response_vote',
'voteGranted': granted,
'term': self.persist['currentTerm']
}
self.raft.send_peer(peer, response)
def on_peer_append_entries(self, peer, msg):
term_is_current = msg['term'] >= self.persist['currentTerm']
prev_log_term_match = msg['prevLogTerm'] is None or \
self.log.term(msg['prevLogIndex']) == msg['prevLogTerm']
success = term_is_current and prev_log_term_match
if term_is_current:
self.restart_election_timer()
if 'compact_data' in msg:
self.log = LogManager(compact_count=msg['compact_count'],
compact_term=msg['compact_term'],
compact_data=msg['compact_data'])
self.volatile['leaderId'] = msg['leaderId']
logger.info('Initialized Log with compact data from leader')
elif success:
self.log.append_entries(msg['entries'], msg['prevLogIndex'])
self.log.commit(msg['leaderCommit'])
self.volatile['leaderId'] = msg['leaderId']
logging.info(f'Log index is now {self.log.index}')
else:
logging.warning("Could not append entries. cause: %s", 'wrong term' \
if not term_is_current else 'prev log term mismatch')
self._update_cluster()
resp = {
'type': 'response_append',
'success': success,
'term': self.persist['currentTerm'],
'matchIndex': self.log.index
}
self.raft.send_peer(peer, resp)
class Candidate(Follower):
def __init__(self, old_state=None, raft=None):
super().__init__(old_state, raft)
self.persist['currentTerm'] += 1
self.vote_count = 0
logging.info("new election Term: %s", self.persist['currentTerm'])
self.send_vote_requests()
def vote_self():
self.persist['voteFor'] = self.volatile['address']
self.on_peer_response_vote(
self.volatile['address'], {'voteGranted': True})
loop = asyncio.get_event_loop()
loop.call_soon(vote_self)
def send_vote_requests(self):
logging.info('Broadcasting request_vote')
msg = {
'type': 'request_vote',
'term': self.persist['currentTerm'],
'candidateId': self.volatile['address'],
'lastLogIndex': self.log.index,
'lastLogTerm': self.log.term()}
self.raft.broadcast_peers(msg)
def on_peer_append_entries(self, peer, msg):
logging.info("Converting to Follower")
self.raft.change_state(Follower)
self.raft.state.on_peer_append_entries(peer, msg)
def on_peer_response_vote(self, peer, msg):
self.vote_count += msg['voteGranted']
logging.info(f'Vote count: {self.vote_count}')
if self.vote_count > len(self.volatile['cluster']) / 2:
self.raft.change_state(Leader)
class Leader(State):
def __init__(self, old_state=None, raft=None):
super().__init__(old_state, raft)
logging.info("Leader of term: %s", self.persist['currentTerm'])
self.volatile['leaderId'] = self.volatile['address']
self.matchIndex = {p: 0 for p in self.volatile['cluster']}
self.nextIndex = {p: self.log.commitIndex + 1 for p in self.matchIndex}
self.waiting_clients = {}
self.send_append_entries()
if 'cluster' not in self.log.state_machine:
self.log.append_entries(
[{
'term': self.persist['currentTerm'],
'data': {'key': 'cluster',
'value': tuple(self.volatile['cluster']),
'action': 'change'
}
}], self.log.index)
self.log.commit(self.log.index)
def teardown(self):
self.append_timer.cancel()
if hasattr(self, 'config_timer'):
self.config_timer.cancel()
def send_append_entries(self):
for peer in self.volatile['cluster']:
if peer == self.volatile['address']:
continue
msg = {'type': 'append_entries',
'term': self.persist['currentTerm'],
'leaderCommit': self.log.commitIndex,
'leaderId': self.volatile['address'],
'prevLogIndex': self.nextIndex[peer] - 1,
'entries': self.log[self.nextIndex[peer]: self.nextIndex[peer] + 100]}
msg.update({'prevLogTerm': self.log.term(msg['prevLogIndex'])})
if self.nextIndex[peer] <= self.log.compacted.index:
msg.update({"compact_data": self.log.compacted.data})
msg.update({"compact_term": self.log.compacted.term})
msg.update({"compact_count": self.log.compacted.count})
logging.info('Sending %s entries to %s. Start index %s', len(msg['entries']), peer,
self.nextIndex[peer])
self.raft.send_peer(peer, msg)
timeout = randrange(1, 4) * 10 ** -1
loop = asyncio.get_event_loop()
self.append_timer = loop.call_later(timeout, self.send_append_entries)
def on_peer_response_append(self, peer, msg):
if msg['success']:
self.matchIndex[peer] = msg['matchIndex']
self.nextIndex[peer] = msg['matchIndex'] + 1
self.matchIndex[self.volatile['address']] = self.log.index
self.nextIndex[self.volatile['address']] = self.log.index + 1
index = statistics.median_low(self.matchIndex.values())
self.log.commit(index)
self.send_client_append_response()
else:
self.nextIndex[peer] = max(0, self.nextIndex[peer] - 1)
def on_client_config(self, protocol, msg):
""" Push new cluster config. When uncommitted cluster changes
are already present, retries until they are committed
before proceding."""
pending_configs = tuple(filter(lambda x: x['data']['key'] == 'cluster',
self.log[self.log.commitIndex + 1:]
))
if pending_configs:
timeout = randrange(1, 4) * 10 ** -1
loop = asyncio.get_event_loop()
self.config_timer = loop.call_later(timeout, self.on_client_append, msg)
return
success = True
cluster = set(self.volatile['cluster'])
peer = (msg['address'], int(msg['port']))
if msg['action'] == 'add' and peer not in cluster:
logger.info('adding node %s', peer)
cluster.add(peer)
self.nextIndex[peer] = 0
self.matchIndex[peer] = 0
elif msg['action'] == 'delete' and peer in cluster:
logger.info(f'Removing node {peer}')
cluster.remove(peer)
del self.nextIndex[peer]
del self.matchIndex[peer]
else:
success = False
if success:
self.log.append_entries(
[{'term': self.persist['currentTerm'],
'data': {'key': 'cluster', 'value': tuple(cluster), 'action': 'change'}
}],
self.log.index
)
self.volatile['cluster'] = cluster
protocol.send({'type': 'result', 'success': success})
def on_client_append(self, protocol, msg):
entry = {'term': self.persist['currentTerm'], 'data': msg['data']}
if msg['data']['key'] == 'cluster':
protocol.send({'type': 'result', 'success': False})
return
self.log.append_entries([entry], self.log.index)
if self.log.index in self.waiting_clients:
self.waiting_clients[self.log.index].append(protocol)
else:
self.waiting_clients[self.log.index] = [protocol]
self.on_peer_response_append(
self.volatile['address'], {'success': True, 'matchIndex': self.log.commitIndex}
)
def on_client_get(self, protocol, msg):
state_machine = self.log.state_machine.data.copy()
protocol.send(state_machine)
def send_client_append_response(self):
to_delete = []
for client_index, clients in self.waiting_clients.items():
if client_index <= self.log.commitIndex:
for client in clients:
client.send({'type': 'result', 'success': True})
logger.info("Sent successful response to client")
to_delete.append(client_index)
for index in to_delete:
del self.waiting_clients[index]