1.zookeeper启动入口
在zkServer.sh的启动命令中，我们可以找到zookeeper启动的关键类org.apache.zookeeper.server.quorum.QuorumPeerMain
QuorumPeerMain#main
我们可以直接看org.apache.zookeeper.server.quorum.QuorumPeerMain中的main方法，从下面的main方法中，我们可以看到初始化了一个QuorumPeerMain对象，并进行调用initializeAndRun方法
public static void main(String[] args) {
QuorumPeerMain main = new QuorumPeerMain();
try {
main.initializeAndRun(args);
} catch (IllegalArgumentException e) {
LOG.error("Invalid arguments, exiting abnormally", e);
LOG.info(USAGE);
System.err.println(USAGE);
System.exit(2);
} catch (ConfigException e) {
LOG.error("Invalid config, exiting abnormally", e);
System.err.println("Invalid config, exiting abnormally");
System.exit(2);
} catch (DatadirException e) {
LOG.error("Unable to access datadir, exiting abnormally", e);
System.err.println("Unable to access datadir, exiting abnormally");
System.exit(3);
} catch (AdminServerException e) {
LOG.error("Unable to start AdminServer, exiting abnormally", e);
System.err.println("Unable to start AdminServer, exiting abnormally");
System.exit(4);
} catch (Exception e) {
LOG.error("Unexpected exception, exiting abnormally", e);
System.exit(1);
}
LOG.info("Exiting normally");
System.exit(0);
}
QuorumPeerMain#initializeAndRun
我们紧接看这个initializeAndRun方法，方法里的代码如下：
protected void initializeAndRun(String[] args)
throws ConfigException, IOException, AdminServerException
{
QuorumPeerConfig config = new QuorumPeerConfig();
if (args.length == 1) {
//解析参数信息
config.parse(args[0]);
}
// Start and schedule the the purge task
// 启动一个定时任务进行定时清理日志信息
DatadirCleanupManager purgeMgr = new DatadirCleanupManager(config
.getDataDir(), config.getDataLogDir(), config
.getSnapRetainCount(), config.getPurgeInterval());
purgeMgr.start();
if (args.length == 1 && config.isDistributed()) {
//作为集群启动
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
// 如果没有配置文件的信息的话，就单机进行启动
ZooKeeperServerMain.main(args);
}
}QuorumPeerMain#runFromConfig
在上面的initializeAndRun方法中我们看到了zookeeper 根据配置文件进行判断是否是单机启动还是集群启动，这块我们就按照集群启动的方式进行启动。我们紧接看这个runFromConfig方法。
public void runFromConfig(QuorumPeerConfig config)
throws IOException, AdminServerException
{
/注册log4j的bean
try {
ManagedUtil.registerLog4jMBeans();
} catch (JMException e) {
LOG.warn("Unable to register log4j JMX control", e);
}
//从这块进行开始启动quorum peer 一个quorum peer就对应着一个zookeeper机器节点
LOG.info("Starting quorum peer, myid=" + config.getServerId());
try {
//创建网络连接工厂
ServerCnxnFactory cnxnFactory = null;
ServerCnxnFactory secureCnxnFactory = null;
if (config.getClientPortAddress() != null) {
cnxnFactory = ServerCnxnFactory.createFactory();
cnxnFactory.configure(config.getClientPortAddress(),
config.getMaxClientCnxns(),
false);
}
if (config.getSecureClientPortAddress() != null) {
secureCnxnFactory = ServerCnxnFactory.createFactory();
secureCnxnFactory.configure(config.getSecureClientPortAddress(),
config.getMaxClientCnxns(),
true);
}
//从这开始就是对quorumPeer的属性的设置
//里面有很多属性暂时可以先不了解
// 一个Zookeeper主节点的启动
quorumPeer = getQuorumPeer();
//磁盘数据管理组件
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());
// zk的内存数据库
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.sh
