zookeeper筆記之基於zk實現分佈式鎖

時間  2019-11-06
標籤 zookeeper 筆記 基於 實現 分佈式 欄目 Zookeeper 简体版
原文   原文鏈接

 

1、分佈式鎖概述

Java中基於AQS框架提供了一系列的鎖，可是當須要在集羣中的多臺機器上互斥執行一段代碼或使用資源時Java提供的這種單機鎖就沒了用武之地，此時須要使用分佈式鎖協調它們。分佈式鎖有不少實現，基於redis、基於數據庫等等，本次討論的是基於zk實現分佈式鎖。html

免責聲明：下面的分佈式鎖是本人學習zk時根據其特性摸索出來的實現，並不表明業內權威作法，僅做爲不一樣的思想碰撞出靈感的小火花之用，若有錯誤之處還望多多指教。java

2、不可重入的分佈式鎖（有羊羣效應，不公平鎖）

首先比較容易想到的就是約定一個路徑的建立做爲搶佔鎖的條件，好比路徑/zk-lock/foo，而後集羣中每臺機器上的程序都嘗試去建立這樣一個臨時節點，誰建立成功了誰就搶到了鎖，沒有建立成功的把本身休眠，休眠以前在/zk-lock/foo節點上添加watcher，watcher中當/zk-lock/foo節點被刪除時將本身叫醒從新搶佔鎖，一直重複這個過程直到全部線程都搶到過鎖。node

再來講搶到鎖的機器，這臺機器搶到鎖以後就開始執行一些業務邏輯等亂七八糟的事情，執行完以後須要unlock釋放鎖，這裏所謂的釋放鎖實際上就是將/zk-lock/foo節點刪除，以前說過了其它沒有搶到鎖的機器都在這個節點上面添加了一個watcher，因此刪除/zk-lock/foo實際上就是將其它休眠的機器喚醒讓它們從新搶佔鎖。redis

上述過程流程圖：數據庫

image

代碼實現，首先是分佈式鎖的接口定義：apache

package cc11001100.zookeeper.lock;

/**
 * @author CC11001100
 */
public interface DistributeLock {

	void lock() throws InterruptedException;

	void unlock();

	/**
	 * 釋放此分佈式鎖所須要的資源，好比zookeeper鏈接
	 */
	void releaseResource();

}

按上述流程圖對分佈式鎖的一個實現：網絡

package cc11001100.zookeeper.lock;

import cc11001100.zookeeper.utils.ZooKeeperUtil;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.UUID;

/**
 * 不可重入有羊羣效應的分佈式鎖（不公平鎖）
 *
 * @author CC11001100
 */
public class NotReentrantDistributeLockWithHerdEffect implements DistributeLock {

	private final Thread currentThread;

	private String lockBasePath;
	private String lockName;
	private String lockFullPath;

	private ZooKeeper zooKeeper;
	private String myId;
	private String myName;

	public NotReentrantDistributeLockWithHerdEffect(String lockBasePath, String lockName) throws IOException {
		this.lockBasePath = lockBasePath;
		this.lockName = lockName;
		this.lockFullPath = this.lockBasePath + "/" + lockName;
		this.zooKeeper = ZooKeeperUtil.getZooKeeper();
		this.currentThread = Thread.currentThread();
		this.myId = UUID.randomUUID().toString();
		this.myName = Thread.currentThread().getName();
		createLockBasePath();
	}

	private void createLockBasePath() {
		try {
			if (zooKeeper.exists(lockBasePath, null) == null) {
				zooKeeper.create(lockBasePath, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
			}
		} catch (KeeperException | InterruptedException ignored) {
		}
	}

	@Override
	public void lock() throws InterruptedException {
		try {
			zooKeeper.create(lockFullPath, myId.getBytes(StandardCharsets.UTF_8), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
			System.out.println(myName + ": get lock");
		} catch (KeeperException.NodeExistsException e) {
			// 若是節點已經存在，則監聽此節點，當節點被刪除時再搶佔鎖
			try {
				zooKeeper.exists(lockFullPath, event -> {
					synchronized (currentThread) {
						currentThread.notify();
						System.out.println(myName + ": wake");
					}
				});
			} catch (KeeperException.NoNodeException e1) {
				// 間不容髮之際，其它人釋放了鎖
				lock();
			} catch (KeeperException | InterruptedException e1) {
				e1.printStackTrace();
			}
			synchronized (currentThread) {
				currentThread.wait();
			}
			lock();
		} catch (KeeperException | InterruptedException e) {
			e.printStackTrace();
		}
	}

	@Override
	public void unlock() {
		try {
			byte[] nodeBytes = zooKeeper.getData(lockFullPath, false, null);
			String currentHoldLockNodeId = new String(nodeBytes, StandardCharsets.UTF_8);
			// 只有當前鎖的持有者是本身的時候，才能刪除節點
			if (myId.equalsIgnoreCase(currentHoldLockNodeId)) {
				zooKeeper.delete(lockFullPath, -1);
			}
		} catch (KeeperException | InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println(myName + ": releaseResource lock");
	}

	@Override
	public void releaseResource() {
		try {
			// 將zookeeper鏈接釋放掉
			zooKeeper.close();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}

}

測試代碼以下：框架

package cc11001100.zookeeper.lock;

import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.concurrent.TimeUnit;

/**
 * @author CC11001100
 */
public class NotReentrantDistributeLockWithHerdEffectTest {

	private static String now() {
		return LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
	}

	public static void main(String[] args) {
		int nodeNum = 10;
		for (int i = 0; i < nodeNum; i++) {
			new Thread(() -> {
				DistributeLock lock = null;
				try {
					lock = new NotReentrantDistributeLockWithHerdEffect("/zk-lock", "foo");
					lock.lock();
					String myName = Thread.currentThread().getName();
					System.out.println(myName + ": hold lock, now=" + now());
					TimeUnit.SECONDS.sleep(3);
					lock.unlock();
				} catch (IOException | InterruptedException e) {
					e.printStackTrace();
				} finally {
					if (lock != null) {
						lock.releaseResource();
					}
				}
			}, "thread-name-" + i).start();
		}

//		output:
//		thread-name-8: get lock
//		thread-name-8: hold lock, now=2019-01-14 13:31:48
//		thread-name-8: releaseResource lock
//		thread-name-2: wake
//		thread-name-5: wake
//		thread-name-3: wake
//		thread-name-1: wake
//		thread-name-4: wake
//		thread-name-9: wake
//		thread-name-0: wake
//		thread-name-7: wake
//		thread-name-6: wake
//		thread-name-2: get lock
//		thread-name-2: hold lock, now=2019-01-14 13:31:51
//		thread-name-7: wake
//		thread-name-2: releaseResource lock
//		thread-name-6: wake
//		thread-name-0: wake
//		thread-name-9: wake
//		thread-name-1: wake
//		thread-name-3: wake
//		thread-name-5: wake
//		thread-name-4: wake
//		thread-name-0: get lock
//		thread-name-0: hold lock, now=2019-01-14 13:31:54
//		thread-name-6: wake
//		thread-name-1: wake
//		thread-name-7: wake
//		thread-name-4: wake
//		thread-name-3: wake
//		thread-name-5: wake
//		thread-name-0: releaseResource lock
//		thread-name-9: wake
//		thread-name-1: get lock
//		thread-name-1: hold lock, now=2019-01-14 13:31:57
//		thread-name-9: wake
//		thread-name-6: wake
//		thread-name-7: wake
//		thread-name-3: wake
//		thread-name-5: wake
//		thread-name-4: wake
//		thread-name-1: releaseResource lock
//		thread-name-9: get lock
//		thread-name-9: hold lock, now=2019-01-14 13:32:00
//		thread-name-7: wake
//		thread-name-4: wake
//		thread-name-5: wake
//		thread-name-3: wake
//		thread-name-9: releaseResource lock
//		thread-name-6: wake
//		thread-name-3: get lock
//		thread-name-3: hold lock, now=2019-01-14 13:32:03
//		thread-name-6: wake
//		thread-name-5: wake
//		thread-name-4: wake
//		thread-name-3: releaseResource lock
//		thread-name-7: wake
//		thread-name-6: get lock
//		thread-name-6: hold lock, now=2019-01-14 13:32:06
//		thread-name-7: wake
//		thread-name-6: releaseResource lock
//		thread-name-4: wake
//		thread-name-5: wake
//		thread-name-7: get lock
//		thread-name-7: hold lock, now=2019-01-14 13:32:09
//		thread-name-4: wake
//		thread-name-7: releaseResource lock
//		thread-name-5: wake
//		thread-name-5: get lock
//		thread-name-5: hold lock, now=2019-01-14 13:32:12
//		thread-name-5: releaseResource lock
//		thread-name-4: wake
//		thread-name-4: get lock
//		thread-name-4: hold lock, now=2019-01-14 13:32:15
//		thread-name-4: releaseResource lock

	}

}

 

3、不可重入的分佈式鎖（無羊羣效應，公平鎖）

上面實現的代碼雖然實現了基本的鎖的功能，可是它有一個比較致命的問題，就是當釋放鎖的時候會把其它全部機器所有喚醒，可是最終只有一臺機器會搶到鎖，沒搶到的還得繼續休眠，尤爲是當機器數比較多的時候，叫醒了好幾十臺機器，結果仍是隻有一臺機器可以搶到鎖（堪比12306的搶票難度...），可是不公平鎖就是這樣啊，須要你們一塊兒搶，不然怎麼能體現出不公平呢，這個現象被稱爲羊羣效應。dom

其實這個問題能夠變通一下，參考Java中AQS框架的CLH隊列的實現，咱們可讓其排隊，每臺機器來搶鎖的時候都要排隊，排隊的時候領一個號碼稱爲本身的ticket，這個ticket是有序的，每次增長1，因此只須要前面的人釋放鎖的時候叫醒後面的第一我的就能夠了，即每臺機器在領完號碼的時候都往本身前面的機器的ticket上添加一個watcher，當前面的執行完業務邏輯釋放鎖的時候將本身叫醒，當前面沒有人的時候說明已經輪到了本身，即直接得到了鎖，關於獲取前面一我的的ticket，由於ticket是每次遞增1的，因此徹底能夠經過本身的ticket計算出前面一我的的ticket，沒必需要非獲取父節點下的全部children。而後就是號碼的發放，使用zookeeper的順序臨時節點能夠保證每次發放的號碼都是有序的，同時當持有鎖的機器意外掛掉的時候可以自動釋放鎖。分佈式

上述過程流程圖：

image

代碼實現：

package cc11001100.zookeeper.lock;

import cc11001100.zookeeper.utils.ZooKeeperUtil;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

import java.io.IOException;

/**
 * 不可重入沒有羊羣效應的鎖（公平鎖）
 *
 * @author CC11001100
 */
public class NotReentrantDistributeLock implements DistributeLock {

	private final Thread currentThread;

	private String lockBasePath;
	private String lockPrefix;
	private String lockFullPath;

	private ZooKeeper zooKeeper;
	private String myName;
	private int myTicket;

	public NotReentrantDistributeLock(String lockBasePath, String lockPrefix) throws IOException {
		this.lockBasePath = lockBasePath;
		this.lockPrefix = lockPrefix;
		this.lockFullPath = lockBasePath + "/" + lockPrefix;
		this.zooKeeper = ZooKeeperUtil.getZooKeeper();
		this.currentThread = Thread.currentThread();
		this.myName = currentThread.getName();
		createLockBasePath();
	}

	private void createLockBasePath() {
		try {
			if (zooKeeper.exists(lockBasePath, null) == null) {
				zooKeeper.create(lockBasePath, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
			}
		} catch (KeeperException | InterruptedException ignored) {
		}
	}

	@Override
	public void lock() throws InterruptedException {
		log("begin get lock");
		try {
			String path = zooKeeper.create(lockFullPath, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
			myTicket = extractMyTicket(path);
			String previousNode = buildPath(myTicket - 1);
			Stat exists = zooKeeper.exists(previousNode, event -> {
				synchronized (currentThread) {
					currentThread.notify();
					log("wake");
				}
			});
			if (exists != null) {
				synchronized (currentThread) {
					currentThread.wait();
				}
			}
			log("get lock success");
		} catch (KeeperException e) {
			e.printStackTrace();
		}
	}

	private int extractMyTicket(String path) {
		int splitIndex = path.lastIndexOf("/");
		return Integer.parseInt(path.substring(splitIndex + 1).replace(lockPrefix, ""));
	}

	private String buildPath(int ticket) {
		return String.format("%s%010d", lockFullPath, ticket);
	}

	@Override
	public void unlock() {
		log("begin release lock");
		try {
			zooKeeper.delete(buildPath(myTicket), -1);
		} catch (KeeperException | InterruptedException e) {
			e.printStackTrace();
		}
		log("end release lock");
	}

	@Override
	public void releaseResource() {
		try {
			// 將zookeeper鏈接釋放掉
			zooKeeper.close();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}

	private void log(String msg) {
		System.out.printf("[%d] %s : %s\n", myTicket, myName, msg);
	}

}

測試代碼：

package cc11001100.zookeeper.lock;

import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.concurrent.TimeUnit;

/**
 * @author CC11001100
 */
public class NotReentrantDistributeLockTest {

	private static String now() {
		return LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
	}

	public static void main(String[] args) {

		int nodeNum = 10;
		for (int i = 0; i < nodeNum; i++) {
			new Thread(() -> {
				DistributeLock lock = null;
				try {
					lock = new NotReentrantDistributeLock("/zk-lock", "bar");
					lock.lock();
					String myName = Thread.currentThread().getName();
					System.out.println(myName + ": get lock success, now=" + now());
					TimeUnit.SECONDS.sleep(3);
					lock.unlock();
				} catch (IOException | InterruptedException e) {
					e.printStackTrace();
				} finally {
					if (lock != null) {
						lock.releaseResource();
					}
				}
			}, "thread-name-" + i).start();
		}

//		output:
//		[0] thread-name-6 : begin get lock
//		[0] thread-name-3 : begin get lock
//		[0] thread-name-5 : begin get lock
//		[0] thread-name-4 : begin get lock
//		[0] thread-name-8 : begin get lock
//		[0] thread-name-9 : begin get lock
//		[0] thread-name-2 : begin get lock
//		[0] thread-name-7 : begin get lock
//		[0] thread-name-1 : begin get lock
//		[0] thread-name-0 : begin get lock
//		[170] thread-name-1 : get lock success
//		thread-name-1: get lock success, now=2019-01-14 17:59:56
//		[170] thread-name-1 : begin release lock
//		[170] thread-name-1 : end release lock
//		[171] thread-name-9 : wake
//		[171] thread-name-9 : get lock success
//		thread-name-9: get lock success, now=2019-01-14 17:59:59
//		[171] thread-name-9 : begin release lock
//		[171] thread-name-9 : end release lock
//		[172] thread-name-4 : wake
//		[172] thread-name-4 : get lock success
//		thread-name-4: get lock success, now=2019-01-14 18:00:02
//		[172] thread-name-4 : begin release lock
//		[173] thread-name-0 : wake
//		[172] thread-name-4 : end release lock
//		[173] thread-name-0 : get lock success
//		thread-name-0: get lock success, now=2019-01-14 18:00:05
//		[173] thread-name-0 : begin release lock
//		[174] thread-name-6 : wake
//		[173] thread-name-0 : end release lock
//		[174] thread-name-6 : get lock success
//		thread-name-6: get lock success, now=2019-01-14 18:00:08
//		[174] thread-name-6 : begin release lock
//		[175] thread-name-7 : wake
//		[174] thread-name-6 : end release lock
//		[175] thread-name-7 : get lock success
//		thread-name-7: get lock success, now=2019-01-14 18:00:11
//		[175] thread-name-7 : begin release lock
//		[176] thread-name-3 : wake
//		[175] thread-name-7 : end release lock
//		[176] thread-name-3 : get lock success
//		thread-name-3: get lock success, now=2019-01-14 18:00:14
//		[176] thread-name-3 : begin release lock
//		[177] thread-name-8 : wake
//		[176] thread-name-3 : end release lock
//		[177] thread-name-8 : get lock success
//		thread-name-8: get lock success, now=2019-01-14 18:00:17
//		[177] thread-name-8 : begin release lock
//		[178] thread-name-2 : wake
//		[177] thread-name-8 : end release lock
//		[178] thread-name-2 : get lock success
//		thread-name-2: get lock success, now=2019-01-14 18:00:20
//		[178] thread-name-2 : begin release lock
//		[179] thread-name-5 : wake
//		[178] thread-name-2 : end release lock
//		[179] thread-name-5 : get lock success
//		thread-name-5: get lock success, now=2019-01-14 18:00:23
//		[179] thread-name-5 : begin release lock
//		[179] thread-name-5 : end release lock

	}

}

 

4、可重入的分佈式鎖（無羊羣效應，公平鎖）

咱們的鎖實現得愈來愈好了，可是它還有一個比較致命的問題，就是它不能重入，所謂的重入就是遞歸獲取鎖，當已經持有鎖時再嘗試獲取鎖時，可重入鎖會直接獲取成功，同時將重入次數加1，當釋放鎖時，將重入次數減1，只有當重入次數爲0時才完全釋放掉鎖。而上面的鎖屬於不可重入鎖，當嘗試遞歸獲取鎖時會產生死鎖永遠等待下去，這很明顯是不合理的，這一小節就討論一下如何將上一節的不可重入鎖轉換爲重入鎖。

其實個人想法很簡單，首先可以肯定的是確定須要在哪裏保存鎖的重入次數，由於已經得到了鎖的機器的重入次數並不須要讓其它機器知道，其它機器只要知道如今鎖在這哥們手裏攥着就能夠了，因此能夠簡單的將重入次數做爲DistributeLock的一個成員變量，好比叫作reentrantCount，每次嘗試獲取鎖的時候先判斷這個變量是否不爲0，若是不爲0的話說明當前機器已經得到了鎖，根據重入鎖的特性，直接將重入次數加1便可，只有當reentrantCount爲0的時候才須要去排隊等待獲取鎖。還有釋放鎖的時候也是判斷當前reentrantCount的值，若是這個值不爲0的話說明當前仍是在遞歸嵌套中，直接將reentrantCount減1便可，而後判斷reentrantCount的值若是爲0的話說明鎖的全部重入都已經釋放掉了，直接將當前鎖的ticket刪除，由於隊列中的後一臺機器已經在當前的ticket上添加了watcher，因此刪除當前ticket的動做至關於叫醒下一個排隊的人。

上述過程流程圖：

image

代碼實現：

package cc11001100.zookeeper.lock;

import cc11001100.zookeeper.utils.ZooKeeperUtil;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

/**
 * 可重入無羊羣效應的分佈式鎖（公平鎖）
 *
 * @author CC11001100
 */
public class ReentrantDistributeLock implements DistributeLock {

	private final Thread currentThread;

	private String lockBasePath;
	private String lockPrefix;
	private String lockFullPath;

	private ZooKeeper zooKeeper;
	private String myName;
	private int myTicket;

	// 使用一個本機變量記載重複次數，這個值就不存儲在zookeeper上了，
	// 一則修改zk節點值還須要網絡會慢一些，二是其它節點只須要知道有個節點當前持有鎖就能夠了，至於重入幾回不關它們的事呀
	private int reentrantCount = 0;

	public ReentrantDistributeLock(String lockBasePath, String lockName) throws IOException {
		this.lockBasePath = lockBasePath;
		this.lockPrefix = lockName;
		this.lockFullPath = lockBasePath + "/" + lockName;
		this.zooKeeper = ZooKeeperUtil.getZooKeeper();
		this.currentThread = Thread.currentThread();
		this.myName = currentThread.getName();
		createLockBasePath();
	}

	private void createLockBasePath() {
		try {
			if (zooKeeper.exists(lockBasePath, null) == null) {
				zooKeeper.create(lockBasePath, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
			}
		} catch (KeeperException | InterruptedException ignored) {
		}
	}

	@Override
	public void lock() throws InterruptedException {
		log("begin get lock");

		// 若是reentrantCount不爲0說明當前節點已經持有鎖了，無需等待，直接增長重入次數便可
		if (reentrantCount != 0) {
			reentrantCount++;
			log("get lock success");
			return;
		}

		// 說明尚未獲取到鎖，須要設置watcher監聽上一個節點釋放鎖事件
		try {
			String path = zooKeeper.create(lockFullPath, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
			myTicket = extractMyTicket(path);
			String previousNode = buildPathByTicket(myTicket - 1);
			Stat exists = zooKeeper.exists(previousNode, event -> {
				synchronized (currentThread) {
					currentThread.notify();
					log("wake");
				}
			});
			if (exists != null) {
				synchronized (currentThread) {
					currentThread.wait();
				}
			}
			reentrantCount++;
			log("get lock success");
		} catch (KeeperException e) {
			e.printStackTrace();
		}
	}

	private int extractMyTicket(String path) {
		int splitIndex = path.lastIndexOf("/");
		return Integer.parseInt(path.substring(splitIndex + 1).replace(lockPrefix, ""));
	}

	private String buildPathByTicket(int ticket) {
		return String.format("%s%010d", lockFullPath, ticket);
	}

	@Override
	public void unlock() {
		log("begin release lock");

		// 每次unlock的時候將遞歸次數減1，沒有減到0說明還在遞歸中
		reentrantCount--;
		if (reentrantCount != 0) {
			log("end release lock");
			return;
		}

		// 只有當重入次數爲0的時候才刪除節點，將鎖釋放掉
		try {
			zooKeeper.delete(buildPathByTicket(myTicket), -1);
		} catch (KeeperException | InterruptedException e) {
			e.printStackTrace();
		}
		log("end release lock");
	}

	@Override
	public void releaseResource() {
		try {
			// 將zookeeper鏈接釋放掉
			zooKeeper.close();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}

	private void log(String msg) {
		System.out.printf("[%s], ticket=%d, reentrantCount=%d, threadName=%s, msg=%s\n", now(), myTicket, reentrantCount, myName, msg);
	}

	private String now() {
		return LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
	}

}

測試代碼：

package cc11001100.zookeeper.lock;

import java.io.IOException;
import java.util.Random;
import java.util.concurrent.TimeUnit;

/**
 * 測試分佈式可重入鎖，每一個鎖隨機重入，看是否會發生錯誤
 *
 * @author CC11001100
 */
public class ReentrantDistributeLockTest {

	public static void main(String[] args) {

		int nodeNum = 10;
		for (int i = 0; i < nodeNum; i++) {
			new Thread(() -> {
				DistributeLock lock = null;
				try {
					lock = new ReentrantDistributeLock("/zk-lock", "bar");
					lock.lock();
					TimeUnit.SECONDS.sleep(1);

					int reentrantTimes = new Random().nextInt(10);
					int reentrantCount = 0;
					for (int j = 0; j < reentrantTimes; j++) {
						lock.lock();
						reentrantCount++;
						if (Math.random() < 0.5) {
							lock.unlock();
							reentrantCount--;
						}
					}
					while (reentrantCount-- > 0) {
						lock.unlock();
					}

					lock.unlock();
				} catch (IOException | InterruptedException e) {
					e.printStackTrace();
				} finally {
					if (lock != null) {
						lock.releaseResource();
					}
				}
			}, "thread-name-" + i).start();
		}

//		output:
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-4, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-5, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-8, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-0, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-6, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-1, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-9, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-3, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=0, reentrantCount=0, threadName=thread-name-2, msg=begin get lock
//		[2019-01-14 17:57:43], ticket=160, reentrantCount=1, threadName=thread-name-0, msg=get lock success
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=1, threadName=thread-name-0, msg=begin get lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=get lock success
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=begin release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=1, threadName=thread-name-0, msg=end release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=1, threadName=thread-name-0, msg=begin get lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=get lock success
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=begin get lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=3, threadName=thread-name-0, msg=get lock success
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=3, threadName=thread-name-0, msg=begin release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=end release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=begin get lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=3, threadName=thread-name-0, msg=get lock success
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=3, threadName=thread-name-0, msg=begin release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=end release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=2, threadName=thread-name-0, msg=begin release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=1, threadName=thread-name-0, msg=end release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=1, threadName=thread-name-0, msg=begin release lock
//		[2019-01-14 17:57:44], ticket=160, reentrantCount=0, threadName=thread-name-0, msg=end release lock
//		[2019-01-14 17:57:44], ticket=161, reentrantCount=0, threadName=thread-name-6, msg=wake
//		[2019-01-14 17:57:44], ticket=161, reentrantCount=1, threadName=thread-name-6, msg=get lock success
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=1, threadName=thread-name-6, msg=begin get lock
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=2, threadName=thread-name-6, msg=get lock success
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=2, threadName=thread-name-6, msg=begin get lock
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=3, threadName=thread-name-6, msg=get lock success
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=3, threadName=thread-name-6, msg=begin release lock
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=2, threadName=thread-name-6, msg=end release lock
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=2, threadName=thread-name-6, msg=begin release lock
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=1, threadName=thread-name-6, msg=end release lock
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=1, threadName=thread-name-6, msg=begin release lock
//		[2019-01-14 17:57:45], ticket=162, reentrantCount=0, threadName=thread-name-5, msg=wake
//		[2019-01-14 17:57:45], ticket=161, reentrantCount=0, threadName=thread-name-6, msg=end release lock
//		[2019-01-14 17:57:45], ticket=162, reentrantCount=1, threadName=thread-name-5, msg=get lock success
//		[2019-01-14 17:57:46], ticket=162, reentrantCount=1, threadName=thread-name-5, msg=begin release lock
//		[2019-01-14 17:57:46], ticket=162, reentrantCount=0, threadName=thread-name-5, msg=end release lock
//		[2019-01-14 17:57:46], ticket=163, reentrantCount=0, threadName=thread-name-8, msg=wake
//		[2019-01-14 17:57:46], ticket=163, reentrantCount=1, threadName=thread-name-8, msg=get lock success
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=1, threadName=thread-name-8, msg=begin get lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=2, threadName=thread-name-8, msg=get lock success
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=2, threadName=thread-name-8, msg=begin release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=1, threadName=thread-name-8, msg=end release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=1, threadName=thread-name-8, msg=begin get lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=2, threadName=thread-name-8, msg=get lock success
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=2, threadName=thread-name-8, msg=begin get lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=3, threadName=thread-name-8, msg=get lock success
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=3, threadName=thread-name-8, msg=begin get lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=4, threadName=thread-name-8, msg=get lock success
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=4, threadName=thread-name-8, msg=begin get lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=5, threadName=thread-name-8, msg=get lock success
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=5, threadName=thread-name-8, msg=begin release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=4, threadName=thread-name-8, msg=end release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=4, threadName=thread-name-8, msg=begin release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=3, threadName=thread-name-8, msg=end release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=3, threadName=thread-name-8, msg=begin release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=2, threadName=thread-name-8, msg=end release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=2, threadName=thread-name-8, msg=begin release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=1, threadName=thread-name-8, msg=end release lock
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=1, threadName=thread-name-8, msg=begin release lock
//		[2019-01-14 17:57:47], ticket=164, reentrantCount=0, threadName=thread-name-2, msg=wake
//		[2019-01-14 17:57:47], ticket=163, reentrantCount=0, threadName=thread-name-8, msg=end release lock
//		[2019-01-14 17:57:47], ticket=164, reentrantCount=1, threadName=thread-name-2, msg=get lock success
//		[2019-01-14 17:57:48], ticket=164, reentrantCount=1, threadName=thread-name-2, msg=begin release lock
//		[2019-01-14 17:57:48], ticket=165, reentrantCount=0, threadName=thread-name-9, msg=wake
//		[2019-01-14 17:57:48], ticket=164, reentrantCount=0, threadName=thread-name-2, msg=end release lock
//		[2019-01-14 17:57:48], ticket=165, reentrantCount=1, threadName=thread-name-9, msg=get lock success
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=1, threadName=thread-name-9, msg=begin get lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=2, threadName=thread-name-9, msg=get lock success
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=2, threadName=thread-name-9, msg=begin release lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=1, threadName=thread-name-9, msg=end release lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=1, threadName=thread-name-9, msg=begin get lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=2, threadName=thread-name-9, msg=get lock success
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=2, threadName=thread-name-9, msg=begin get lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=3, threadName=thread-name-9, msg=get lock success
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=3, threadName=thread-name-9, msg=begin release lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=2, threadName=thread-name-9, msg=end release lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=2, threadName=thread-name-9, msg=begin release lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=1, threadName=thread-name-9, msg=end release lock
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=1, threadName=thread-name-9, msg=begin release lock
//		[2019-01-14 17:57:49], ticket=166, reentrantCount=0, threadName=thread-name-1, msg=wake
//		[2019-01-14 17:57:49], ticket=165, reentrantCount=0, threadName=thread-name-9, msg=end release lock
//		[2019-01-14 17:57:49], ticket=166, reentrantCount=1, threadName=thread-name-1, msg=get lock success
//		[2019-01-14 17:57:50], ticket=166, reentrantCount=1, threadName=thread-name-1, msg=begin release lock
//		[2019-01-14 17:57:50], ticket=167, reentrantCount=0, threadName=thread-name-4, msg=wake
//		[2019-01-14 17:57:50], ticket=166, reentrantCount=0, threadName=thread-name-1, msg=end release lock
//		[2019-01-14 17:57:50], ticket=167, reentrantCount=1, threadName=thread-name-4, msg=get lock success
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=1, threadName=thread-name-4, msg=begin get lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=2, threadName=thread-name-4, msg=get lock success
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=2, threadName=thread-name-4, msg=begin release lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=1, threadName=thread-name-4, msg=end release lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=1, threadName=thread-name-4, msg=begin get lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=2, threadName=thread-name-4, msg=get lock success
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=2, threadName=thread-name-4, msg=begin get lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=3, threadName=thread-name-4, msg=get lock success
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=3, threadName=thread-name-4, msg=begin release lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=2, threadName=thread-name-4, msg=end release lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=2, threadName=thread-name-4, msg=begin release lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=1, threadName=thread-name-4, msg=end release lock
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=1, threadName=thread-name-4, msg=begin release lock
//		[2019-01-14 17:57:51], ticket=168, reentrantCount=0, threadName=thread-name-3, msg=wake
//		[2019-01-14 17:57:51], ticket=167, reentrantCount=0, threadName=thread-name-4, msg=end release lock
//		[2019-01-14 17:57:51], ticket=168, reentrantCount=1, threadName=thread-name-3, msg=get lock success
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=1, threadName=thread-name-3, msg=begin get lock
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=2, threadName=thread-name-3, msg=get lock success
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=2, threadName=thread-name-3, msg=begin get lock
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=3, threadName=thread-name-3, msg=get lock success
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=3, threadName=thread-name-3, msg=begin release lock
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=2, threadName=thread-name-3, msg=end release lock
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=2, threadName=thread-name-3, msg=begin release lock
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=1, threadName=thread-name-3, msg=end release lock
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=1, threadName=thread-name-3, msg=begin release lock
//		[2019-01-14 17:57:52], ticket=169, reentrantCount=0, threadName=thread-name-7, msg=wake
//		[2019-01-14 17:57:52], ticket=168, reentrantCount=0, threadName=thread-name-3, msg=end release lock
//		[2019-01-14 17:57:52], ticket=169, reentrantCount=1, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=1, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=2, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=2, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=2, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=2, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=5, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=5, threadName=thread-name-7, msg=begin get lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=6, threadName=thread-name-7, msg=get lock success
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=6, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=5, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=5, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=4, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=3, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=2, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=2, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=1, threadName=thread-name-7, msg=end release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=1, threadName=thread-name-7, msg=begin release lock
//		[2019-01-14 17:57:53], ticket=169, reentrantCount=0, threadName=thread-name-7, msg=end release lock

	}

}

 

.

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