【4. Zookeeper单节点源码解读】

启动客户端 zkCli.sh 文件里面的配置

# use POSIX interface, symlink is followed automatically
ZOOBIN="${BASH_SOURCE-$0}"
ZOOBIN="$(dirname "${ZOOBIN}")"
ZOOBINDIR="$(cd "${ZOOBIN}"; pwd)"

if [ -e "$ZOOBIN/../libexec/zkEnv.sh" ]; then
  . "$ZOOBINDIR"/../libexec/zkEnv.sh
else
  . "$ZOOBINDIR"/zkEnv.sh
fi

ZOO_LOG_FILE=zookeeper-$USER-cli-$HOSTNAME.log

"$JAVA" "-Dzookeeper.log.dir=${ZOO_LOG_DIR}" "-Dzookeeper.root.logger=${ZOO_LOG4J_PROP}" "-Dzookeeper.log.file=${ZOO_LOG_FILE}" 
     -cp "$CLASSPATH" $CLIENT_JVMFLAGS $JVMFLAGS 
     org.apache.zookeeper.ZooKeeperMain "$@"

开始的Main

// org.apache.zookeeper.ZooKeeperMain#main
public static void main(String[] args) throws IOException, InterruptedException {
    ZooKeeperMain main = new ZooKeeperMain(args);
    main.run();
}

Main 方法流程：

1. new ZooKeeperMain 对象
2. 调用 run（）方法

在 ZookeeperMain 的构造方法里面，重点是

public ZooKeeperMain(String args[]) throws IOException, InterruptedException { 
    cl.parseOptions(args);
	System.out.println("Connecting to " + cl.getOption("server"));
	// 连 接 上 
    ZK connectToZK(cl.getOption("server"));
}

protected void connectToZK(String newHost) throws InterruptedException, IOException { 
    if (zk != null && zk.getState().isAlive()) {
		zk.close();
	}
	host = newHost;
	boolean readonly = cl.getOption("readonly") != null; 
    zk = new ZooKeeper(host,Integer.parseInt(cl.getOption("timeout")), new MyWatcher(), readOnly);
}

最终在 connectToZK 方法里面也就是使用原生的 Zk 客户端进行连接的

public ZooKeeper(String connectString, int sessionTimeout, Watcher watcher, boolean canBeReadOnly)
throws IOException{
	LOG.info("Initiating client connection, connectString=" + connectString + " sessionTimeout=" + sessionTimeout + " watcher=" + watcher); 
    watchManager.defaultWatcher = watcher;
	ConnectStringParser connectStringParser = new ConnectStringParser( connectString);
	HostProvider hostProvider = new StaticHostProvider(
	connectStringParser.getServerAddresses());
	cnxn = new ClientCnxn(connectStringParser.getChrootPath(), hostProvider, sessionTimeout, this, 			watchManager,
	//获得和服务端连接的对象
	getClientCnxnSocket(), canBeReadOnly);
	//调用 start() 
    cnxn.start();
}

public void start() { 
    sendThread.start();
    eventThread.start();
}

org.apache.zookeeper.ClientCnxn.SendThread#run

org.apache.zookeeper.ClientCnxn.EventThread.run