Zookeeper启动过程

启动脚本：zookeeper-3.3.5/bin/zkServer.sh

入口类：org.apache.zookeeper.server.quorum.QuorumPeerMain

1、若传入了配置文件路径，则进行解析；

2、开启清理数据及快照文件的定时任务：

      删除前缀为log.或snapshot. 且 非最近的snapRetainCount（至少为3）个文件

  class MyFileFilter implements FileFilter{
            private final String prefix;
            MyFileFilter(String prefix){
                this.prefix=prefix;
            }
            public boolean accept(File f){
                if(!f.getName().startsWith(prefix) || exclude.contains(f))
                    return false;
                return true;
            }
        }
  List<File> files=new ArrayList<File>(Arrays.asList(txnLog.getDataDir().listFiles(new MyFileFilter("log."))));
  files.addAll(Arrays.asList(txnLog.getSnapDir().listFiles(new MyFileFilter("snapshot."))));

3、通过配置文件运行 runFromConfig(config);

public void runFromConfig(QuorumPeerConfig config) throws IOException {
      try {
          ManagedUtil.registerLog4jMBeans();
      } catch (JMException e) {
          LOG.warn("Unable to register log4j JMX control", e);
      }
 
      LOG.info("Starting quorum peer");
      try {
          ServerCnxnFactory cnxnFactory = ServerCnxnFactory.createFactory();
          cnxnFactory.configure(config.getClientPortAddress(),
                                config.getMaxClientCnxns());
 
          quorumPeer = new QuorumPeer();
          quorumPeer.setClientPortAddress(config.getClientPortAddress());
          quorumPeer.setTxnFactory(new FileTxnSnapLog(
                      new File(config.getDataLogDir()),
                      new File(config.getDataDir())));
          quorumPeer.setQuorumPeers(config.getServers());
          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.setQuorumVerifier(config.getQuorumVerifier());
          quorumPeer.setCnxnFactory(cnxnFactory);
          quorumPeer.setZKDatabase(new ZKDatabase(quorumPeer.getTxnFactory()));
          quorumPeer.setLearnerType(config.getPeerType());
 
          quorumPeer.start();
          quorumPeer.join();
      } catch (InterruptedException e) {
          // warn, but generally this is ok
          LOG.warn("Quorum Peer interrupted", e);
      }
    }

        quorumPeer.start()方法：

        1）加载快照及提交日志数据；

        2） ServerCnxnFactory 对象start；

              ServerCnxnFactory的实现有NIO模式和Netty模式，可通过zookeeper.serverCnxnFactory配置项来指定，默认是NIO模式；        

        3）开始leader选举；

          

4、若无配置文件或无集群，则以单机模式运行ZooKeeperServerMain.main(args);

public static void main(String[] args) {
        ZooKeeperServerMain main = new ZooKeeperServerMain();
        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 (Exception e) {
            LOG.error("Unexpected exception, exiting abnormally", e);
            System.exit(1);
        }
        LOG.info("Exiting normally");
        System.exit(0);
    }