zookeeper源码分析-选举算法
欢迎查看Eetal的第二十五篇博客–zookeeper源码分析-选举算法
入口类
启动zookeeper后输入java命令jps，查看到线程运行的主类为QuoRumPeerMain
QuoRumPeerMain的启动方法根据启动命令传递的参数，读取配置文件去解析，根据是单机还是集群使用不同的方法运行
protected void initializeAndRun(String[] args)
throws ConfigException, IOException, AdminServerException
{
QuorumPeerConfig config = new QuorumPeerConfig();
if (args.length == 1) {
config.parse(args[0]);
}
// Start and schedule the the purge task
DatadirCleanupManager purgeMgr = new DatadirCleanupManager(config
.getDataDir(), config.getDataLogDir(), config
.getSnapRetainCount(), config.getPurgeInterval());
purgeMgr.start();
//如果是集群模式，使用runFromConfig方法，否则使用ZooKeeperServerMain.main方法运行
if (args.length == 1 && config.isDistributed()) {
runFromConfig(config);
} else {
LOG.warn("Either no config or no quorum defined in config, running "
+ " in standalone mode");
// there is only server in the quorum -- run as standalone
ZooKeeperServerMain.main(args);
}
}
集群运行
runFromConfig方法根据传递进来的配置信息，绑定成员quorumPeer，加载属性
quorumPeer.setQuorumVerifier(config.getQuorumVerifier(), false)这一句代码加载的QuorumVerifier包含了从配置文件解析来的集群中所有成员的信息对象
public void runFromConfig(QuorumPeerConfig config)
throws IOException, AdminServerException
{
......
quorumPeer = getQuorumPeer();
quorumPeer.setTxnFactory(new FileTxnSnapLog(
config.getDataLogDir(),
config.getDataDir()));
quorumPeer.enableLocalSessions(config.areLocalSessionsEnabled());
quorumPeer.enableLocalSessionsUpgrading(
config.isLocalSessionsUpgradingEnabled());
//quorumPeer.setQuorumPeers(config.getAllMembers());
quorumPeer.setElectionType(config.getElectionAlg());
quorumPeer.setMyid(config.getServerId());
quorumPeer.setTickTime(config.getTickTime());
quorumPeer.setMinSessionTimeout(config.getMinSessionTimeout());
quorumPeer.setMaxSessionTimeout(config.getMaxSessionTimeout());
quorumPeer.setInitLimit(config.getInitLimit());
quorumPeer.setSyncLimit(config.getSyncLimit());
quorumPeer.setConfigFileName(config.getConfigFilename());
quorumPeer.setZKDatabase(new ZKDatabase(quorumPeer.getTxnFactory()));
quorumPeer.setQuorumVerifier(config.getQuorumVerifier(), false);
if (config.getLastSeenQuorumVerifier()!=null) {
quorumPeer.setLastSeenQuorumVerifier(config.getLastSeenQuorumVerifier(), false);
}
quorumPeer.initConfigInZKDatabase();
quorumPeer.setCnxnFactory(cnxnFactory);
quorumPeer.setSecureCnxnFactory(secureCnxnFactory);
quorumPeer.setSslQuorum(config.isSslQuorum());
quorumPeer.setUsePortUnification(config.shouldUsePortUnification());
quorumPeer.setLearnerType(config.getPeerType());
quorumPeer.setSyncEnabled(config.getSyncEnabled());
quorumPeer.setQuorumListenOnAllIPs(config.getQuorumListenOnAllIPs());
if (config.sslQuorumReloadCertFiles) {
quorumPeer.getX509Util().enableCertFileReloading();
}
// sets quorum sasl authentication configurations
quorumPeer.setQuorumSaslEnabled(config.quorumEnableSasl);
if(quorumPeer.isQuorumSaslAuthEnabled()){
quorumPeer.setQuorumServerSaslRequired(config.quorumServerRequireSasl);
quorumPeer.setQuorumLearnerSaslRequired(config.quorumLearnerRequireSasl);
quorumPeer.setQuorumServicePrincipal(config.quorumServicePrincipal);
quorumPeer.setQuorumServerLoginContext(config.quorumServerLoginContext);
quorumPeer.setQuorumLearnerLoginContext(config.quorumLearnerLoginContext);
}
quorumPeer.setQuorumCnxnThreadsSize(config.quorumCnxnThreadsSize);
quorumPeer.initialize();
quorumPeer.start();
quorumPeer.join();
......
}
public interface QuorumVerifier {
long getWeight(long id);
boolean containsQuorum(Set<Long> set);
long getVersion();
void setVersion(long ver);
Map<Long, QuorumServer> getAllMembers();//全部集群成员
Map<Long, QuorumServer> getVotingMembers();//参与投票成员
Map<Long, QuorumServer> getObservingMembers();//观察者成员
boolean equals(Object o);
String toString();
}
接下来调用start方法开始运行QuorumPeer线程成员
start方法被重写了，在开始运行前做了一些处理
@Override
public synchronized void start() {
if (!getView().containsKey(myid)) {
//getView是根据前面配置信息解析设置的QuorumVerifier，获取全部集群机器的id和ip端口信息
//此处判断当前机器是否在集群里
throw new RuntimeException("My id " + myid + " not in the peer list");
}
loadDataBase();//从数据日志文件恢复数据到内存
......
startLeaderElection();//开启选举
super.start();//线程类的start方法，开始运行run
}
选举运行，此时刚进入集群节点状态为LOOKING，第一票投票给自己
public class QuorumPeerConfig {
protected int electionAlg = 3;
}
synchronized public void startLeaderElection() {
......
if (getPeerState() == ServerState.LOOKING) {
//投票给自己
currentVote = new Vote(myid, getLastLoggedZxid(), getCurrentEpoch());
}
......
this.electionAlg = createElectionAlgorithm(electionType);//挑选选举算法---配置文件不设置默认为3
}
protected Election createElectionAlgorithm(int electionAlgorithm){
Election le=null;
//TODO: use a factory rather than a switch
switch (electionAlgorithm) {
case 0:
le = new LeaderElection(this);
break;
case 1:
le = new AuthFastLeaderElection(this);
break;
case 2:
le = new AuthFastLeaderElection(this, true);
break;
case 3:
QuorumCnxManager qcm = createCnxnManager();
QuorumCnxManager oldQcm = qcmRef.getAndSet(qcm);
if (oldQcm != null) {
LOG.warn("Clobbering already-set QuorumCnxManager (restarting leader election?)");
oldQcm.halt();
}
QuorumCnxManager.Listener listener = qcm.listener;
if(listener != null){
listener.start();
FastLeaderElection fle = new FastLeaderElection(this, qcm);
fle.start();
le = fle;
} else {
LOG.error("Null listener when initializing cnx manager");
}
break;
default:
assert false;
}
return le;
}
zookeeper依赖jmx去实现集群操作，会将自身的运行线程quorumPeer封装为一个QuorumBean，通过MBeanRegistry注册到jmx上
MBeanRegistry是zookeeper封装了对MBeanServer的一些操作的一个类，主要完成对objectName的自动生成
MBeanRegistry注册时要指定parent，根据parent会自动生成objectName
rmi与MBean相关的源码分析请参照本人的另外两篇博客：
1.java-rmi源码解析java-rmi源码解析
2.MBean与JMXMBean与JMX
public class MBeanRegistry {
private static final Logger LOG = LoggerFactory.getLogger(MBeanRegistry.class);
private static volatile MBeanRegistry instance = new MBeanRegistry();
private final Object LOCK = new Object();
private Map<ZKMBeanInfo, String> mapBean2Path =
new ConcurrentHashMap<ZKMBeanInfo, String>();
private MBeanServer mBeanServer;
/**
* Useful for unit tests. Change the MBeanRegistry instance
*
* @param instance new instance
*/
public static void setInstance(MBeanRegistry instance) {
MBeanRegistry.instance = instance;
}
public static MBeanRegistry getInstance() {
return instance;
}
public MBeanRegistry () {
try {
mBeanServer = ManagementFactory.getPlatformMBeanServer();
} catch (Error e) {
// Account for running within IKVM and create a new MBeanServer
// if the PlatformMBeanServer does not exist.
mBeanServer = MBeanServerFactory.createMBeanServer();
}
}
/**
* Return the underlying MBeanServer that is being
* used to register MBean's. The returned MBeanServer
* may be a new empty MBeanServer if running through IKVM.
*/
public MBeanServer getPlatformMBeanServer() {
return mBeanServer;
}
/**
* Registers a new MBean with the platform MBean server.
* @param bean the bean being registered
* @param parent if not null, the new bean will be registered as a child
* node of this parent.
*/
public void register(ZKMBeanInfo bean, ZKMBeanInfo parent)
throws JMException
{
assert bean != null;
String path = null;
if (parent != null) {
path = mapBean2Path.get(parent);
assert path != null;
}
path = makeFullPath(path, parent);
if(bean.isHidden())
return;
ObjectName oname = makeObjectName(path, bean);
try {
synchronized (LOCK) {
mBeanServer.registerMBean(bean, oname);
mapBean2Path.put(bean, path);
}
} catch (JMException e) {
LOG.warn("Failed to register MBean " + bean.getName());
throw e;
}
}
run方法细节，将本地的jmxQuorumBean注册到jmx，并且根据读取配置文件的集群信息，把每个远程节点的信息封装以后，以本机节点jmxQuorumBean为parent，注册到Jmx上
接下来因为状态为欸LOOKING，进入选举方法
setCurrentVote(makeLEStrategy().lookForLeader());
@Override
public void run() {
updateThreadName();
jmxQuorumBean = new QuorumBean(this);
MBeanRegistry.getInstance().register(jmxQuorumBean, null);
for(QuorumServer s: getView().values()){
ZKMBeanInfo p;
if (getId() == s.id) {
p = jmxLocalPeerBean = new LocalPeerBean(this);
try {
MBeanRegistry.getInstance().register(p, jmxQuorumBean);
} catch (Exception e) {
LOG.warn("Failed to register with JMX", e);
jmxLocalPeerBean = null;
}
} else {
RemotePeerBean rBean = new RemotePeerBean(this, s);
try {
MBeanRegistry.getInstance().register(rBean, jmxQuorumBean);
jmxRemotePeerBean.put(s.id, rBean);
} catch (Exception e) {
LOG.warn("Failed to register with JMX", e);
}
}
}
/*
* Main loop
*/
while (running) {
switch (getPeerState()) {
case LOOKING:
LOG.info("LOOKING");
if (Boolean.getBoolean("readonlymode.enabled")) {
LOG.info("Attempting to start ReadOnlyZooKeeperServer");
// Create read-only server but don't start it immediately
final ReadOnlyZooKeeperServer roZk =
new ReadOnlyZooKeeperServer(logFactory, this, this.zkDb);
// Instead of starting roZk immediately, wait some grace
// period before we decide we're partitioned.
//
// Thread is used here because otherwise it would require
// changes in each of election strategy classes which is
// unnecessary code coupling.
Thread roZkMgr = new Thread() {
public void run() {
try {
// lower-bound grace period to 2 secs
sleep(Math.max(2000, tickTime));
if (ServerState.LOOKING.equals(getPeerState())) {
roZk.startup();
}
} catch (InterruptedException e) {
LOG.info("Interrupted while attempting to start ReadOnlyZooKeeperServer, not started");
} catch (Exception e) {
LOG.error("FAILED to start ReadOnlyZooKeeperServer", e);
}
}
};
try {
roZkMgr.start();
reconfigFlagClear();
if (shuttingDownLE) {
shuttingDownLE = false;
startLeaderElection();
}
setCurrentVote(makeLEStrategy().lookForLeader());
} catch (Exception e) {
LOG.warn("Unexpected exception", e);
setPeerState(ServerState.LOOKING);
} finally {
// If the thread is in the the grace period, interrupt
// to come out of waiting.
roZkMgr.interrupt();
roZk.shutdown();
}
} else {
try {
reconfigFlagClear();
if (shuttingDownLE) {
shuttingDownLE = false;
startLeaderElection();
}
setCurrentVote(makeLEStrategy().lookForLeader());
} catch (Exception e) {
LOG.warn("Unexpected exception", e);
setPeerState(ServerState.LOOKING);
}
}
break;
.....
}
......
}
根据前面分析得知，使用的默认选举策略为FastLeaderElection
FastLeaderElection构造时会实例化一个Messager
Messenger实例化时会创建两个线程，一个负责接收消息，一个负责发送消息启动两个线程，一个负责接收消息，一个负责发送消息
而FastLeaderElection对象前面挑选选举算法时，构建完成就会调用start方法，对应会启动两个工作线程开始接收和发送消息
public FastLeaderElection(QuorumPeer self, QuorumCnxManager manager){
this.stop = false;
this.manager = manager;
starter(self, manager);
}
LinkedBlockingQueue<ToSend> sendqueue;
LinkedBlockingQueue<Notification> recvqueue;
/**
* This method is invoked by the constructor. Because it is a
* part of the starting procedure of the object that must be on
* any constructor of this class, it is probably best to keep as
* a separate method. As we have a single constructor currently,
* it is not strictly necessary to have it separate.
*
* @param self QuorumPeer that created this object
* @param manager Connection manager
*/
private void starter(QuorumPeer self, QuorumCnxManager manager) {
this.self = self;
proposedLeader = -1;
proposedZxid = -1;
sendqueue = new LinkedBlockingQueue<ToSend>();
recvqueue = new LinkedBlockingQueue<Notification>();
this.messenger = new Messenger(manager);
}
Messenger(QuorumCnxManager manager) {
this.ws = new WorkerSender(manager);
this.wsThread = new Thread(this.ws,
"WorkerSender[myid=" + self.getId() + "]");
this.wsThread.setDaemon(true);
this.wr = new WorkerReceiver(manager);
this.wrThread = new Thread(this.wr,
"WorkerReceiver[myid=" + self.getId() + "]");
this.wrThread.setDaemon(true);
}
/**
* Starts instances of WorkerSender and WorkerReceiver
*/
void start(){
this.wsThread.start();
this.wrThread.start();
}
该策略为搜寻收到的消息，如果收到的消息的epoch大于当前epoch（朝代），更新本地保存的朝代，直接清空所有的接受消息，对比消息投票属性和自己的初始化属性，如果对方胜出，则将投票改为选举对方挑选的leader，否则投票给自己（初始化时的id-myid）
以下为对比方法（epoch都是peerEpoch)
((newEpoch > curEpoch) ||
((newEpoch == curEpoch) &&
((newZxid > curZxid) || ((newZxid == curZxid) && (newId > curId)))))
胜出条件:
1.朝代大于当前朝代
2.朝代相等，并且zxid大的 或者 （zxid相等并且id更大的）----------因为zxid代表事务id，更大相当于对方处理了更多的leader消息
当没有新的投票消息时，则继续发送自己的投票消息（sendNotification方法实际只是将消息加入阻塞队列，真正进行发送处理的是另一个WorkerSender线程子类实例，该线程循环获取阻塞队列的消息，进行发送，对应的接受消息是WorkerReader线程子类实例）
public Vote lookForLeader() throws InterruptedException {
try {
self.jmxLeaderElectionBean = new LeaderElectionBean();
MBeanRegistry.getInstance().register(
self.jmxLeaderElectionBean, self.jmxLocalPeerBean);
} catch (Exception e) {
LOG.warn("Failed to register with JMX", e);
self.jmxLeaderElectionBean = null;
}
if (self.start_fle == 0) {
self.start_fle = Time.currentElapsedTime();
}
try {
HashMap<Long, Vote> recvset = new HashMap<Long, Vote>();
HashMap<Long, Vote> outofelection = new HashMap<Long, Vote>();
int notTimeout = finalizeWait;
synchronized(this){
logicalclock.incrementAndGet();
updateProposal(getInitId(), getInitLastLoggedZxid(), getPeerEpoch());
}
LOG.info("New election. My id = " + self.getId() +
", proposed zxid=0x" + Long.toHexString(proposedZxid));
sendNotifications();
/*
* Loop in which we exchange notifications until we find a leader
*/
while ((self.getPeerState() == ServerState.LOOKING) &&
(!stop)){
/*
* Remove next notification from queue, times out after 2 times
* the termination time
*/
Notification n = recvqueue.poll(notTimeout,
TimeUnit.MILLISECONDS);
/*
* Sends more notifications if haven't received enough.
* Otherwise processes new notification.
*/
if(n == null){
if(manager.haveDelivered()){
//如果全部发送完了，再次发送一次投票信息
sendNotifications();
} else {
//没发送完，可能出现故障，重新连接每一台集群中的机器
manager.connectAll();
}
/*
* Exponential backoff
*/
int tmpTimeOut = notTimeout*2;
notTimeout = (tmpTimeOut < maxNotificationInterval?
tmpTimeOut : maxNotificationInterval);
LOG.info("Notification time out: " + notTimeout);
}
else if (validVoter(n.sid) && validVoter(n.leader)) {
/*
* Only proceed if the vote comes from a replica in the current or next
* voting view for a replica in the current or next voting view.
*/
switch (n.state) {
case LOOKING:
// If notification > current, replace and send messages out
if (n.electionEpoch > logicalclock.get()) {
logicalclock.set(n.electionEpoch);
recvset.clear();
if(totalOrderPredicate(n.leader, n.zxid, n.peerEpoch,
getInitId(), getInitLastLoggedZxid(), getPeerEpoch())) {
updateProposal(n.leader, n.zxid, n.peerEpoch);
} else {
updateProposal(getInitId(),
getInitLastLoggedZxid(),
getPeerEpoch());
}
sendNotifications();
} else if (n.electionEpoch < logicalclock.get()) {
if(LOG.isDebugEnabled()){
LOG.debug("Notification election epoch is smaller than logicalclock. n.electionEpoch = 0x"
+ Long.toHexString(n.electionEpoch)
+ ", logicalclock=0x" + Long.toHexString(logicalclock.get()));
}
break;
} else if (totalOrderPredicate(n.leader, n.zxid, n.peerEpoch,
proposedLeader, proposedZxid, proposedEpoch)) {
updateProposal(n.leader, n.zxid, n.peerEpoch);
sendNotifications();
}
if(LOG.isDebugEnabled()){
LOG.debug("Adding vote: from=" + n.sid +
", proposed leader=" + n.leader +
", proposed zxid=0x" + Long.toHexString(n.zxid) +
", proposed election epoch=0x" + Long.toHexString(n.electionEpoch));
}
// don't care about the version if it's in LOOKING state
recvset.put(n.sid, new Vote(n.leader, n.zxid, n.electionEpoch, n.peerEpoch));
if (termPredicate(recvset,
new Vote(proposedLeader, proposedZxid,
logicalclock.get(), proposedEpoch))) {
// Verify if there is any change in the proposed leader
while((n = recvqueue.poll(finalizeWait,
TimeUnit.MILLISECONDS)) != null){
if(totalOrderPredicate(n.leader, n.zxid, n.peerEpoch,
proposedLeader, proposedZxid, proposedEpoch)){
recvqueue.put(n);
break;
}
}
/*
* This predicate is true once we don't read any new
* relevant message from the reception queue
*/
if (n == null) {
self.setPeerState((proposedLeader == self.getId()) ?
ServerState.LEADING: learningState());
Vote endVote = new Vote(proposedLeader,
proposedZxid, logicalclock.get(),
proposedEpoch);
leaveInstance(endVote);
return endVote;
}
}
break;
......
}
} else {
if (!validVoter(n.leader)) {
LOG.warn("Ignoring notification for non-cluster member sid {} from sid {}", n.leader, n.sid);
}
if (!validVoter(n.sid)) {
LOG.warn("Ignoring notification for sid {} from non-quorum member sid {}", n.leader, n.sid);
}
}
}
return null;
} finally {
try {
if(self.jmxLeaderElectionBean != null){
MBeanRegistry.getInstance().unregister(
self.jmxLeaderElectionBean);
}
} catch (Exception e) {
LOG.warn("Failed to unregister with JMX", e);
}
self.jmxLeaderElectionBean = null;
LOG.debug("Number of connection processing threads: {}",
manager.getConnectionThreadCount());
}
}
投票以后会进入选举是否完成的判断,如果确定选举有了结果就会设置自身的状态并结束选举
if (termPredicate(recvset,
new Vote(proposedLeader, proposedZxid,
logicalclock.get(), proposedEpoch))) {
// Verify if there is any change in the proposed leader
while((n = recvqueue.poll(finalizeWait,
TimeUnit.MILLISECONDS)) != null){
if(totalOrderPredicate(n.leader, n.zxid, n.peerEpoch,
proposedLeader, proposedZxid, proposedEpoch)){
recvqueue.put(n);
break;
}
}
/*
* This predicate is true once we don't read any new
* relevant message from the reception queue
*/
if (n == null) {
self.setPeerState((proposedLeader == self.getId()) ?
ServerState.LEADING: learningState());
Vote endVote = new Vote(proposedLeader,
proposedZxid, logicalclock.get(),
proposedEpoch);
leaveInstance(endVote);
return endVote;
}
}
protected boolean termPredicate(Map<Long, Vote> votes, Vote vote) {
SyncedLearnerTracker voteSet = new SyncedLearnerTracker();
voteSet.addQuorumVerifier(self.getQuorumVerifier());
if (self.getLastSeenQuorumVerifier() != null
&& self.getLastSeenQuorumVerifier().getVersion() > self
.getQuorumVerifier().getVersion()) {
voteSet.addQuorumVerifier(self.getLastSeenQuorumVerifier());
}
/*
* First make the views consistent. Sometimes peers will have different
* zxids for a server depending on timing.
*/
for (Map.Entry<Long, Vote> entry : votes.entrySet()) {
if (vote.equals(entry.getValue())) {
voteSet.addAck(entry.getKey());
}
}
return voteSet.hasAllQuorums();
}
SyncedLearnerTracker中投票结果的判定是这样实现的
public boolean hasAllQuorums() {
for (QuorumVerifierAcksetPair qvAckset : qvAcksetPairs) {
if (!qvAckset.getQuorumVerifier().containsQuorum(qvAckset.getAckset()))
return false;
}
return true;
}
而 在QuorumPeerConfig加载配置文件解析时就实例化，根据使用带权重的还是不带权重，分别使用QuorumHierarchical和QuorumMaj
void setupQuorumPeerConfig(Properties prop, boolean configBackwardCompatibilityMode)
throws IOException, ConfigException {
quorumVerifier = parseDynamicConfig(prop, electionAlg, true, configBackwardCompatibilityMode);
setupMyId();
setupClientPort();
setupPeerType();
checkValidity();
}
public static QuorumVerifier parseDynamicConfig(Properties dynamicConfigProp, int eAlg, boolean warnings,
boolean configBackwardCompatibilityMode) throws IOException, ConfigException {
boolean isHierarchical = false;
for (Entry<Object, Object> entry : dynamicConfigProp.entrySet()) {
String key = entry.getKey().toString().trim();
if (key.startsWith("group") || key.startsWith("weight")) {
isHierarchical = true;
} else if (!configBackwardCompatibilityMode && !key.startsWith("server.") && !key.equals("version")){
LOG.info(dynamicConfigProp.toString());
throw new ConfigException("Unrecognised parameter: " + key);
}
}
QuorumVerifier qv = createQuorumVerifier(dynamicConfigProp, isHierarchical);
int numParticipators = qv.getVotingMembers().size();
int numObservers = qv.getObservingMembers().size();
if (numParticipators == 0) {
if (!standaloneEnabled) {
throw new IllegalArgumentException("standaloneEnabled = false then " +
"number of participants should be >0");
}
if (numObservers > 0) {
throw new IllegalArgumentException("Observers w/o participants is an invalid configuration");
}
} else if (numParticipators == 1 && standaloneEnabled) {
// HBase currently adds a single server line to the config, for
// b/w compatibility reasons we need to keep this here. If standaloneEnabled
// is true, the QuorumPeerMain script will create a standalone server instead
// of a quorum configuration
LOG.error("Invalid configuration, only one server specified (ignoring)");
if (numObservers > 0) {
throw new IllegalArgumentException("Observers w/o quorum is an invalid configuration");
}
} else {
if (warnings) {
if (numParticipators <= 2) {
LOG.warn("No server failure will be tolerated. " +
"You need at least 3 servers.");
} else if (numParticipators % 2 == 0) {
LOG.warn("Non-optimial configuration, consider an odd number of servers.");
}
}
/*
* If using FLE, then every server requires a separate election
* port.
*/
if (eAlg != 0) {
for (QuorumServer s : qv.getVotingMembers().values()) {
if (s.electionAddr == null)
throw new IllegalArgumentException(
"Missing election port for server: " + s.id);
}
}
}
return qv;
}
private static QuorumVerifier createQuorumVerifier(Properties dynamicConfigProp, boolean isHierarchical) throws ConfigException{
if(isHierarchical){
return new QuorumHierarchical(dynamicConfigProp);
} else {
/*
* The default QuorumVerifier is QuorumMaj
*/
//LOG.info("Defaulting to majority quorums");
return new QuorumMaj(dynamicConfigProp);
}
}
简单分析QuorumMaj，其判断作为leader的条件就是得票数超过一半
public QuorumMaj(Properties props) throws ConfigException {
for (Entry<Object, Object> entry : props.entrySet()) {
String key = entry.getKey().toString();
String value = entry.getValue().toString();
if (key.startsWith("server.")) {
int dot = key.indexOf('.');
long sid = Long.parseLong(key.substring(dot + 1));
QuorumServer qs = new QuorumServer(sid, value);
allMembers.put(Long.valueOf(sid), qs);
if (qs.type == LearnerType.PARTICIPANT)
votingMembers.put(Long.valueOf(sid), qs);
else {
observingMembers.put(Long.valueOf(sid), qs);
}
} else if (key.equals("version")) {
version = Long.parseLong(value, 16);
}
}
half = votingMembers.size() / 2;
}
public boolean containsQuorum(Set<Long> ackSet) {
return (ackSet.size() > half);
}
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