paxos算法java实现_基于python的Paxos算法实现

理解一个算法最快，最深刻的做法，我觉着可能是自己手动实现，虽然项目中不用自己实现，有已经封装好的算法库，供我们调用，我觉着还是有必要自己亲自实践一下。

这里首先说明一下，python这种动态语言，对不熟悉的人可能看着比较别扭，不像java那样参数类型是固定的，所以看着会有些蛋疼。这里环境用的是python2.7。

class Message:

# command

MSG_ACCEPTOR_AGREE = 0 # 追随者约定

MSG_ACCEPTOR_ACCEPT = 1 # 追随者接受

MSG_ACCEPTOR_REJECT = 2 # 追随者拒绝-网络不通

MSG_ACCEPTOR_UNACCEPT = 3 # 追随者网络通-不同意

MSG_ACCEPT = 4 # 接受

MSG_PROPOSE = 5 # 提议

MSG_EXT_PROPOSE = 6 # 额外提议

MSG_HEARTBEAT = 7 # 心跳，每隔一段时间同步消息

def __init__(self, command=None):

self.command = command

# 把收到的消息原原路返回，作为应答消息

def copyAsReply(self, message):

# 提议ID #当前的ID #发给谁 #谁发的

self.proposalID, self.instanceID, self.to, self.source = message.proposalID, message.instanceID, message.source, message.to

self.value = message.value # 发的信息

然后是利用socket,线程和队列实现的消息处理器：

# 基于socket传递消息，封装网络传递消息

import threading

import pickle

import socket

import queue

class MessagePump(threading.Thread):

# 收取消息线程

class MPHelper(threading.Thread):

def __init__(self, owner):

self.owner = owner

threading.Thread.__init__(self)

def run(self):

while not self.owner.abort: # 只要所有者线程没有结束,一直接受消息

try:

(bytes, addr) = self.owner.socket.recvfrom(2048) # 收取消息

msg = pickle.loads(bytes) # 读取二进制数据转化为消息

msg.source = addr[1]

self.owner.queue.put(msg) # 队列存入消息

except Exception as e:

pass

def __init__(self, owner, port, timeout=2):

threading.Thread.__init__(self)

self.owner = owner

self.abort = False

self.timeout = 2

self.port = port

self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # UDP通信

self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 200000) # 通信参数

self.socket.bind(("localhost", port)) # 通信地址，ip，端口

self.socket.settimeout(timeout) # 超时设置

self.queue = queue.Queue() # 队列

self.helper = MessagePump.MPHelper(self) # 接收消息

# 运行主线程

def run(self):

self.helper.start() # 开启收消息的线程

while not self.abort:

message = self.waitForMessage() # 阻塞等待

self.owner.recvMessage(message) # 收取消息

# 等待消息

def waitForMessage(self):

try:

msg = self.queue.get(True, 3) # 抓取数据，最多等待3s

return msg

except:

return None

# 发送消息

def sendMessage(self, message):

bytes = pickle.dumps(message) # 转化为二进制

address = ("localhost", message.to) # 地址ip,端口(ip,port)

self.socket.sendto(bytes, address)

return True

#是否停止收取消息

def doAbort(self):

self.abort = True

再来一个消息处理器，模拟消息的传递，延迟，丢包，其实这个类没什么卵用，这个是为模拟测试准备的

from MessagePump import MessagePump

import random

class AdversarialMessagePump(MessagePump): # 类的继承

# 对抗消息传输，延迟消息并任意顺序传递,模拟网络的延迟，消息传送并不是顺序

def __init__(self, owner, port, timeout=2):

MessagePump.__init__(self, owner, port, timeout) # 初始化父类

self.messages = set() # 集合避免重复

def waitForMessage(self):

try:

msg = self.queue.get(True, 0.1) # 从队列抓取数据

self.messages.add(msg) # 添加消息

except Exception as e: # 处理异常

pass

# print(e)

if len(self.messages) > 0 and random.random() < 0.95: # Arbitrary!

msg = random.choice(list(self.messages)) # 随机抓取消息发送

self.messages.remove(msg) # 删除消息

else:

msg = None

return msg

再来一个是记录类

# InstanceRecord本地记录类，主要记录追随者、领导者最高编号的协议

from PaxosLeaderProtocol import PaxosLeaderProtocol

class InstanceRecord:

def __init__(self):

self.protocols = {}

self.highestID = (-1, -1) # (port,count)

self.value = None

def addProtocol(self, protocol):

self.protocols[protocol.proposalID] = protocol

if protocol.proposalID[1] > self.highestID[1] or (

protocol.proposalID[1] == self.highestID[1] and protocol.proposalID[0] > self.highestID[0]):

self.highestID = protocol.proposalID # 取得编号最大的协议

def getProtocol(self, protocolID):

return self.protocols[protocolID]

def cleanProtocols(self):

keys = self.protocols.keys()

for k in keys:

protocol = self.protocols[k]

if protocol.state == PaxosLeaderProtocol.STATE_ACCEPTED:

print("删除协议")

del self.protocols[k]

下面就是Acceptor的实现：

# 追随者

from MessagePump import MessagePump

from Message import Message

from InstanceRecord import InstanceRecord

from PaxosAcceptorProtocol import PaxosAcceptorProtocol

class PaxosAcceptor:

def __init__(self, port, leaders):

self.port = port

self.leaders = leaders

self.instances = {} # 接口列表

self.msgPump = MessagePump(self, self.port) # 消息传递器

self.failed = False

# 开始消息传送

def start(self):

self.msgPump.start()

# 停止

def stop(self):

self.msgPump.doAbort()

# 失败

def fail(self):

self.failed = True

def recover(self):

self.failed = False

# 发送消息

def sendMessage(self, message):

self.msgPump.sendMessage(message)

# 收消息,只收取为提议的消息

def recvMessage(self, message):

if message == None:

return

if self.failed: # 失败状态不收取消息

return

if message.command == Message.MSG_PROPOSE: # 判断消息是否为提议

if message.instanceID not in self.instances:

record = InstanceRecord() # 记录器

self.instances[message.instanceID] = record

protocol = PaxosAcceptorProtocol(self) # 创建协议

protocol.recvProposal(message) # 收取消息

self.instances[message.instanceID].addProtocol(protocol)

else:

self.instances[message.instanceID].getProtocol(message.proposalID).doTransition(message)

# 通知客户端,

def notifyClient(self, protocol, message):

if protocol.state == PaxosAcceptorProtocol.STATE_PROPOSAL_ACCEPTED: # 提议被接受，通知

self.instances[protocol.instanceID].value = message.value # 储存信息

print(u"协议被客户端接受 %s" % message.value)

# 获取最高同意的建议

def getHighestAgreedProposal(self, instance):

return self.instances[instance].highestID # (port,count)

# 获取接口数据

def getInstanceValue(self, instance):

return self.instances[instance].value

那再看下AcceptorProtocol的实现：

from Message import Message

class PaxosAcceptorProtocol(object):

# State variables

STATE_UNDEFINED = -1 # 协议没有定义的情况0

STATE_PROPOSAL_RECEIVED = 0 # 收到消息

STATE_PROPOSAL_REJECTED = 1 # 拒绝链接

STATE_PROPOSAL_AGREED = 2 # 同意链接

STATE_PROPOSAL_ACCEPTED = 3 # 同意请求

STATE_PROPOSAL_UNACCEPTED = 4 # 拒绝请求

def __init__(self, client):

self.client = client

self.state = PaxosAcceptorProtocol.STATE_UNDEFINED

# 收取,只处理协议类型的消息

def recvProposal(self, message):

if message.command == Message.MSG_PROPOSE: # 协议

self.proposalID = message.proposalID

self.instanceID = message.instanceID

(port, count) = self.client.getHighestAgreedProposal(message.instanceID) # 端口，协议内容的最高编号

# 检测编号处理消息协议

# 判断协议是否最高

if count < self.proposalID[1] or (count == self.proposalID[1] and port < self.proposalID[0]):

self.state = PaxosAcceptorProtocol.STATE_PROPOSAL_AGREED # 协议同意

print("同意协议:%s, %s " % (message.instanceID, message.value))

value = self.client.getInstanceValue(message.instanceID)

msg = Message(Message.MSG_ACCEPTOR_AGREE) # 同意协议

msg.copyAsReply(message)

msg.value = value

msg.sequence = (port, count)

self.client.sendMessage(msg) # 发送消息

else: # 不再接受比最高协议小的提议

self.state = PaxosAcceptorProtocol.STATE_PROPOSAL_REJECTED

return self.proposalID

else:

# 错误重试

pass

# 过度

def doTransition(self, message): # 如果当前协议状态是接受连接，消息类型是接受

if self.state == PaxosAcceptorProtocol.STATE_PROPOSAL_AGREED and message.command == Message.MSG_ACCEPT:

self.state = PaxosAcceptorProtocol.STATE_PROPOSAL_ACCEPTED # 接收协议

msg = Message(Message.MSG_ACCEPTOR_ACCEPT) # 创造消息

msg.copyAsReply(message) # 拷贝并回复

for l in self.client.leaders:

msg.to = l

self.client.sendMessage(msg) # 给领导发送消息

self.notifyClient(message) # 通知自己

return True

raise Exception("并非预期的状态和命令")

# 通知自己客户端

def notifyClient(self, message):

self.client.notifyClient(self, message)

接着看下Leader和LeaderProtocol实现：

# 领导者

import threading

import Queue

import time

from Message import Message

from MessagePump import MessagePump

from InstanceRecord import InstanceRecord

from PaxosLeaderProtocol import PaxosLeaderProtocol

class PaxosLeader:

# 定时监听

class HeartbeatListener(threading.Thread):

def __init__(self, leader):

self.leader = leader

self.queue = Queue.Queue() # 消息队列

self.abort = False

threading.Thread.__init__(self)

def newHB(self, message):

self.queue.put(message)

def doAbort(self):

self.abort = True

def run(self): # 读取消息

elapsed = 0

while not self.abort:

s = time.time()

try:

hb = self.queue.get(True, 2)

# 设定规则，谁的端口号比较高，谁就是领导

if hb.source > self.leader.port:

self.leader.setPrimary(False)

except:

self.leader.setPrimary(True)

# 定时发送

class HeartbeatSender(threading.Thread):

def __init__(self, leader):

threading.Thread.__init__(self)

self.leader = leader

self.abort = False

def doAbort(self):

self.abort = True

def run(self):

while not self.abort:

time.sleep(1)

if self.leader.isPrimary:

msg = Message(Message.MSG_HEARTBEAT)

msg.source = self.leader.port

for leader in self.leader.leaders:

msg.to = leader

self.leader.sendMessage(msg)

def __init__(self, port, leaders=None, acceptors=None):

self.port = port

if leaders == None:

self.leaders = []

else:

self.leaders = leaders

if acceptors == None:

self.acceptors = []

else:

self.acceptors = acceptors

self.group = self.leaders + self.acceptors # 集合合并

self.isPrimary = False # 自身是不是领导

self.proposalCount = 0

self.msgPump = MessagePump(self, port) # 消息传送器

self.instances = {}

self.hbListener = PaxosLeader.HeartbeatListener(self) # 监听

self.hbSender = PaxosLeader.HeartbeatSender(self) # 发送心跳

self.highestInstance = -1 # 协议状态

self.stoped = True # 是否正在运行

self.lasttime = time.time() # 最后一次时间

def sendMessage(self, message):

self.msgPump.sendMessage(message)

def start(self):

self.hbSender.start()

self.hbListener.start()

self.msgPump.start()

self.stoped = False

def stop(self):

self.hbSender.doAbort()

self.hbListener.doAbort()

self.msgPump.doAbort()

self.stoped = True

def setPrimary(self, primary): # 设置领导者

if self.isPrimary != primary:

# Only print if something's changed

if primary:

print(u"我是leader%s" % self.port)

else:

print(u"我不是leader%s" % self.port)

self.isPrimary = primary

# 获取所有的领导下面的追随者

def getGroup(self):

return self.group

def getLeaders(self):

return self.leaders

def getAcceptors(self):

return self.acceptors

# 必须获得1/2以上的人支持

def getQuorumSize(self):

return (len(self.getAcceptors()) / 2) + 1

def getInstanceValue(self, instanceID):

if instanceID in self.instances:

return self.instances[instanceID].value

return None

def getHistory(self): # 历史记录

return [self.getInstanceValue(i) for i in range(1, self.highestInstance + 1)]

# 抓取同意的数量

def getNumAccpted(self):

return len([v for v in self.getHistory() if v != None])

# 抓取空白时间处理下事务

def findAndFillGaps(self):

for i in range(1, self.highestInstance):

if self.getInstanceValue(i) == None:

print("填充空白", i)

self.newProposal(0, i)

self.lasttime = time.time()

# 采集无用信息

def garbageCollect(self):

for i in self.instances:

self.instances[i].cleanProtocols()

# 通知领导

def recvMessage(self, message):

if self.stoped:

return

if message == None:

if self.isPrimary and time.time() - self.lasttime > 15.0:

self.findAndFillGaps()

self.garbageCollect()

return

#处理心跳信息

if message.command == Message.MSG_HEARTBEAT:

self.hbListener.newHB(message)

return True

#处理额外的提议

if message.command == Message.MSG_EXT_PROPOSE:

print("额外的协议", self.port, self.highestInstance)

if self.isPrimary:

self.newProposal(message.value)

return True

if self.isPrimary and message.command != Message.MSG_ACCEPTOR_ACCEPT:

self.instances[message.instanceID].getProtocol(message.proposalID).doTransition(message)

if message.command == Message.MSG_ACCEPTOR_ACCEPT:

if message.instanceID not in self.instances:

self.instances[message.instanceID] = InstanceRecord()

record = self.instances[message.instanceID]

if message.proposalID not in record.protocols:#创建协议

protocol = PaxosLeaderProtocol(self)

protocol.state = PaxosLeaderProtocol.STATE_AGREED

protocol.proposalID = message.proposalID

protocol.instanceID = message.instanceID

protocol.value = message.value

record.addProtocol(protocol)

else:

protocol = record.getProtocol(message.proposalID)

protocol.doTransition(message)

return True

# 新建提议

def newProposal(self, value, instance=None):

protocol = PaxosLeaderProtocol(self)

if instance == None: # 创建协议标号

self.highestInstance += 1

instanceID = self.highestInstance

else:

instanceID = instance

self.proposalCount += 1

id = (self.port, self.proposalCount)

if instanceID in self.instances:

record = self.instances[instanceID]

else:

record = InstanceRecord()

self.instances[instanceID] = record

protocol.propose(value, id, instanceID)

record.addProtocol(protocol)

def notifyLeader(self, protocol, message):

if protocol.state == PaxosLeaderProtocol.STATE_ACCEPTED:

print("协议接口%s被%s接受" % (message.instanceID, message.value))

self.instances[message.instanceID].accepted = True

self.instances[message.instanceID].value = message.value

self.highestInstance = max(message.instanceID, self.highestInstance)

return

if protocol.state == PaxosLeaderProtocol.STATE_REJECTED: # 重新尝试

self.proposalCount = max(self.proposalCount, message.highestPID[1])

self.newProposal(message.value)

return True

if protocol.state == PaxosLeaderProtocol.STATE_UNACCEPTED:

pass

LeaderProtocol实现：

from Message import Message

class PaxosLeaderProtocol(object):

STATE_UNDEFINED = -1 # 协议没有定义的情况0

STATE_PROPOSED = 0 # 协议消息

STATE_REJECTED = 1 # 拒绝链接

STATE_AGREED = 2 # 同意链接

STATE_ACCEPTED = 3 # 同意请求

STATE_UNACCEPTED = 4 # 拒绝请求

def __init__(self, leader):

self.leader = leader

self.state = PaxosLeaderProtocol.STATE_UNDEFINED

self.proposalID = (-1, -1)

self.agreecount, self.acceptcount = (0, 0)

self.rejectcount, self.unacceptcount = (0, 0)

self.instanceID = -1

self.highestseen = (0, 0)

# 提议

def propose(self, value, pID, instanceID):

self.proposalID = pID

self.value = value

self.instanceID = instanceID

message = Message(Message.MSG_PROPOSE)

message.proposalID = pID

message.instanceID = instanceID

message.value = value

for server in self.leader.getAcceptors():

message.to = server

self.leader.sendMessage(message)

self.state = PaxosLeaderProtocol.STATE_PROPOSED

return self.proposalID

# 過度

def doTransition(self, message):

# 根據狀態運行協議

if self.state == PaxosLeaderProtocol.STATE_PROPOSED:

if message.command == Message.MSG_ACCEPTOR_AGREE:

self.agreecount += 1

if self.agreecount >= self.leader.getQuorumSize(): # 选举

print(u"达成协议的法定人数，最后的价值回答是:%s" % message.value)

if message.value != None:

if message.sequence[0] > self.highestseen[0] or (

message.sequence[0] == self.highestseen[0] and message.sequence[1] > self.highestseen[

1]):

self.value = message.value

self.highestseen = message.sequence

self.state = PaxosLeaderProtocol.STATE_AGREED # 同意更新

# 发送同意消息

msg = Message(Message.MSG_ACCEPT)

msg.copyAsReply(message)

msg.value = self.value

msg.leaderID = msg.to

for server in self.leader.getAcceptors():

msg.to = server

self.leader.sendMessage(msg)

self.leader.notifyLeader(self, message)

return True

if message.command == Message.MSG_ACCEPTOR_REJECT:

self.rejectcount += 1

if self.rejectcount >= self.leader.getQuorumSize():

self.state = PaxosLeaderProtocol.STATE_REJECTED

self.leader.notifyLeader(self, message)

return True

if self.state == PaxosLeaderProtocol.STATE_AGREED:

if message.command == Message.MSG_ACCEPTOR_ACCEPT: # 同意协议

self.acceptcount += 1

if self.acceptcount >= self.leader.getQuorumSize():

self.state = PaxosLeaderProtocol.STATE_ACCEPTED # 接受

self.leader.notifyLeader(self, message)

if message.command == Message.MSG_ACCEPTOR_UNACCEPT:

self.unacceptcount += 1

if self.unacceptcount >= self.leader.getQuorumSize():

self.state = PaxosLeaderProtocol.STATE_UNACCEPTED

self.leader.notifyLeader(self, message)

测试模块：

import socket, pickle, time

from Message import Message

from PaxosAcceptor import PaxosAcceptor

from PaxosLeader import PaxosLeader

if __name__ == "__main__":

# 设定5个客户端

numclients = 5

clients = [PaxosAcceptor(port, [54321, 54322]) for port in range(64320, 64320 + numclients)]

# 两个领导者

leader1 = PaxosLeader(54321, [54322], [c.port for c in clients])

leader2 = PaxosLeader(54322, [54321], [c.port for c in clients])

# 开启领导者与追随者

leader1.start()

leader1.setPrimary(True)

leader2.setPrimary(True)

leader2.start()

for c in clients:

c.start()

# 破坏,客户端不链接

clients[0].fail()

clients[1].fail()

# 通信

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # udp协议

start = time.time()

for i in range(1000):

m = Message(Message.MSG_EXT_PROPOSE) # 消息

m.value = 0 + i # 消息参数

m.to = 54322 # 设置传递的端口

bytes = pickle.dumps(m) # 提取的二进制数据

s.sendto(bytes, ("localhost", m.to)) # 发送消息

while leader2.getNumAccpted() < 999:

print("休眠的这一秒 %d " % leader2.getNumAccpted())

time.sleep(1)

print(u"休眠10秒")

time.sleep(10)

print(u"停止leaders")

leader1.stop()

leader2.stop()

print(u"停止客户端")

for c in clients:

c.stop()

print(u"leader1历史纪录")

print(leader1.getHistory())

print(u"leader2历史纪录")

print(leader2.getHistory())

end = time.time()

print(u"一共用了%f秒" % (end - start))

代码确实比较长，看起来有些困难，最好还是在pycharm上看这个逻辑，可以快速定位参数指向，如果有不对的地方欢迎指正

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。

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