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zk中ZooKeeperServer的作用是什么，针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。
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内部类
ChangeRecord 处理PrepRP和FinalRP之间的信息
static class ChangeRecord {
ChangeRecord(long zxid, String path, StatPersisted stat, int childCount, List acl) {
this.zxid = zxid;
this.path = path;
this.stat = stat;
this.childCount = childCount;
this.acl = acl;
}
long zxid;
String path;
StatPersisted stat; /* Make sure to create a new object when changing */
int childCount;
List acl; /* Make sure to create a new object when changing */
ChangeRecord duplicate(long zxid) {
StatPersisted stat = new StatPersisted();
if (this.stat != null) {
DataTree.copyStatPersisted(this.stat, stat);
}
return new ChangeRecord(zxid, path, stat, childCount, acl == null ? new ArrayList<>() : new ArrayList<>(acl));
}
}
protected enum State {
INITIAL,
RUNNING,
SHUTDOWN,
ERROR
}
初始化函数
public ZooKeeperServer(FileTxnSnapLog txnLogFactory, int tickTime, int minSessionTimeout, int maxSessionTimeout, int clientPortListenBacklog, ZKDatabase zkDb, String initialConfig) {
serverStats = new ServerStats(this);
this.txnLogFactory = txnLogFactory;
this.txnLogFactory.setServerStats(this.serverStats);
this.zkDb = zkDb;
this.tickTime = tickTime;
setMinSessionTimeout(minSessionTimeout);
setMaxSessionTimeout(maxSessionTimeout);
this.listenBacklog = clientPortListenBacklog;
listener = new ZooKeeperServerListenerImpl(this);
readResponseCache = new ResponseCache();
connThrottle = new BlueThrottle();
this.initialConfig = initialConfig;
this.requestPathMetricsCollector = new RequestPathMetricsCollector();
this.initLargeRequestThrottlingSettings();
LOG.info("Created server with tickTime " + tickTime
+ " minSessionTimeout " + getMinSessionTimeout()
+ " maxSessionTimeout " + getMaxSessionTimeout()
+ " clientPortListenBacklog " + getClientPortListenBacklog()
+ " datadir " + txnLogFactory.getDataDir()
+ " snapdir " + txnLogFactory.getSnapDir());
} 通过参数构造一个数据管理Log FileTxnSnapLog
public ZooKeeperServer(File snapDir, File logDir, int tickTime) throws IOException {
this(new FileTxnSnapLog(snapDir, logDir), tickTime, "");
}集群和单机中加载数据
集群调用顺序
Leader#lead
ZooKeeperServer#loadData
单机调用顺序
ServerCnxFactory#startUp
ZooKeeperServer#startdata
ZooKeeperServer#loadData
单机版的startData方法
public void startdata() throws IOException, InterruptedException {
//check to see if zkDb is not null
if (zkDb == null) {
zkDb = new ZKDatabase(this.txnLogFactory);//实例化zkdatabase
}
if (!zkDb.isInitialized()) {
loadData();//没有初始化就重新初始化
}
}//加载数据
public void loadData() throws IOException, InterruptedException {
/*
* When a new leader starts executing Leader#lead, it
* invokes this method. The database, however, has been
* initialized before running leader election so that
* the server could pick its zxid for its initial vote.
* It does it by invoking QuorumPeer#getLastLoggedZxid.
* Consequently, we don't need to initialize it once more
* and avoid the penalty of loading it a second time. Not
* reloading it is particularly important for applications
* that host a large database.
*
* The following if block checks whether the database has
* been initialized or not. Note that this method is
* invoked by at least one other method:
* ZooKeeperServer#startdata
*/
//加载信息
if (zkDb.isInitialized()) {
setZxid(zkDb.getDataTreeLastProcessedZxid());
} else {
setZxid(zkDb.loadDataBase());
}
// Clean up dead sessions
//获取超时deadSessions
List deadSessions = new ArrayList<>();
for (Long session : zkDb.getSessions()) {
if (zkDb.getSessionWithTimeOuts().get(session) == null) {
deadSessions.add(session);
}
}
//杀掉session
for (long session : deadSessions) {
// TODO: Is lastProcessedZxid really the best thing to use?
killSession(session, zkDb.getDataTreeLastProcessedZxid());
}
// Make a clean snapshot 创建快照
takeSnapshot();
}
删除会话
protected void killSession(long sessionId, long zxid) {
zkDb.killSession(sessionId, zxid);
if (LOG.isTraceEnabled()) {
ZooTrace.logTraceMessage(
LOG,
ZooTrace.SESSION_TRACE_MASK,
"ZooKeeperServer --- killSession: 0x" + Long.toHexString(sessionId));
}
if (sessionTracker != null) {
sessionTracker.removeSession(sessionId);
}
}
public synchronized void startup() {
if (sessionTracker == null) {
createSessionTracker();
}
//责任链处理
startSessionTracker();
//设置请求处理器
setupRequestProcessors();
startRequestThrottler();
//注册jmx
registerJMX();
startJvmPauseMonitor();
registerMetrics();
//设置状态
setState(State.RUNNING);
requestPathMetricsCollector.start();
localSessionEnabled = sessionTracker.isLocalSessionsEnabled();
notifyAll();
} 关于zk中ZooKeeperServer的作用是什么问题的解答就分享到这里了，希望以上内容可以对大家有一定的帮助，如果你还有很多疑惑没有解开，可以关注创新互联行业资讯频道了解更多相关知识。