Zookeeper服务器单机版启动_port datadir

先来看下ZooKeeper服务端的整体构架。

1.单机版服务器启动

        ZooKeeper服务器的启动，大体分为以下5个步骤：配置文件解析、初始化数据管理器、初始化网络I/O管理器、数据恢复与对外服务。下图为单机版的服务器启动流程。

1.1 预启动

预启动步骤如下。

（1）统一由QuorumPeerMain作为启动类。

         无论是单机版还是集群版，在启动ZooKeeper服务器时，在zkServer.cmd和zkServer.sh两个脚本中，都配置了使用org.apach.zookeeper.server.quorum.QuorumPeerMain作为启动类入口。

public class QuorumPeerMain {
    private static final Logger LOG = LoggerFactory.getLogger(QuorumPeerMain.class);
 
    private static final String USAGE = "Usage: QuorumPeerMain configfile";
 
    protected QuorumPeer quorumPeer;
 
    /**
     * To start the replicated server specify the configuration file name on
     * the command line.
     * @param args path to the configfile
     */
    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 (Exception e) {
            LOG.error("Unexpected exception, exiting abnormally", e);
            System.exit(1);
        }
        LOG.info("Exiting normally");
        System.exit(0);
    }
 
    protected void initializeAndRun(String[] args)
        throws ConfigException, IOException
    {
        QuorumPeerConfig config = new QuorumPeerConfig();
        if (args.length == 1) {
            config.parse(args[0]);  //解析配置文件zoo.cfg
        }
 
        // Start and schedule the the purge task  //创建并启动历史文件清理器
        DatadirCleanupManager purgeMgr = new DatadirCleanupManager(config
                .getDataDir(), config.getDataLogDir(), config
                .getSnapRetainCount(), config.getPurgeInterval());
        purgeMgr.start();
 
        if (args.length == 1 && config.servers.size() > 0) {   //集群模式
            runFromConfig(config); 
        } else {   //单机模式
            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
            ZooKeeperServerMa