一、安装 1.1 下载安装 1、环境准备
ZooKeeper服务器是用Java创建的,它运行在JVM之上。需要安装JDK 7或更高版本。
2、上传
将下载的ZooKeeper放到/opt/ZooKeeper目录下
# 上传zookeeper alt+p put f:/setup/apache-zookeeper-3.5.6-bin.tar.gz # 打开 opt目录 cd /opt # 创建zooKeeper目录 mkdir zooKeeper # 将zookeeper安装包移动到 /opt/zooKeeper mv apache-zookeeper-3.5.6-bin.tar.gz /opt/zookeeper/
3、解压
将tar包解压到/opt/zookeeper目录下
tar -zxvf apache-ZooKeeper-3.5.6-bin.tar.gz
1.2 配置启动 1、配置zoo.cfg
进入到conf目录拷贝一个zoo_sample.cfg并完成配置
# 进入到conf目录 cd /opt/zooKeeper/apache-zooKeeper-3.5.6-bin/conf/ # 拷贝 cp zoo_sample.cfg zoo.cfg
修改zoo.cfg
# 打开目录 cd /opt/zooKeeper/ # 创建zooKeeper存储目录 mkdir zkdata # 修改zoo.cfg vim /opt/zooKeeper/apache-zooKeeper-3.5.6-bin/conf/zoo.cfg
修改存储目录:dataDir=/opt/zookeeper/zkdata
2、启动ZooKeeper
cd /opt/zooKeeper/apache-zooKeeper-3.5.6-bin/bin/ # 启动 ./zkServer.sh start
3、查看ZooKeeper状态
zookeeper启动成功。standalone代表zk没有搭建集群,现在是单节点
二、搭建Zookeeper集群 2.1 搭建要求 真实的集群是需要部署在不同的服务器上的,但是在我们测试时同时启动很多个虚拟机内存会吃不消,所以我们通常会搭建伪集群 ,也就是把所有的服务都搭建在一台虚拟机上,用端口进行区分。
我们这里要求搭建一个三个节点的Zookeeper集群(伪集群)。
2.2 准备工作 重新部署一台虚拟机作为我们搭建集群的测试服务器。
(1)安装JDK 【此步骤省略】。
(2)Zookeeper压缩包上传到服务器 (3)将Zookeeper解压 ,建立/usr/local/zookeeper-cluster目录,将解压后的Zookeeper复制到以下三个目录
/usr/local/zookeeper-cluster/zookeeper-1
/usr/local/zookeeper-cluster/zookeeper-2
/usr/local/zookeeper-cluster/zookeeper-3
[root@localhost ~]# mkdir /usr/local/zookeeper-cluster [root@localhost ~]# cp -r apache-zookeeper-3.5.6-bin /usr/local/zookeeper-cluster/zookeeper-1 [root@localhost ~]# cp -r apache-zookeeper-3.5.6-bin /usr/local/zookeeper-cluster/zookeeper-2 [root@localhost ~]# cp -r apache-zookeeper-3.5.6-bin /usr/local/zookeeper-cluster/zookeeper-3
(4)创建data目录 ,并且将 conf下zoo_sample.cfg 文件改名为 zoo.cfg
mkdir /usr/local/zookeeper-cluster/zookeeper-1/data mkdir /usr/local/zookeeper-cluster/zookeeper-2/data mkdir /usr/local/zookeeper-cluster/zookeeper-3/data mv /usr/local/zookeeper-cluster/zookeeper-1/conf/zoo_sample.cfg /usr/local/zookeeper-cluster/zookeeper-1/conf/zoo.cfg mv /usr/local/zookeeper-cluster/zookeeper-2/conf/zoo_sample.cfg /usr/local/zookeeper-cluster/zookeeper-2/conf/zoo.cfg mv /usr/local/zookeeper-cluster/zookeeper-3/conf/zoo_sample.cfg /usr/local/zookeeper-cluster/zookeeper-3/conf/zoo.cfg
(5) 配置每一个Zookeeper 的dataDir 和 clientPort 分别为2181 2182 2183
修改/usr/local/zookeeper-cluster/zookeeper-1/conf/zoo.cfg
vim /usr/local/zookeeper-cluster/zookeeper-1/conf/zoo.cfg clientPort=2181 dataDir=/usr/local/zookeeper-cluster/zookeeper-1/data
修改/usr/local/zookeeper-cluster/zookeeper-2/conf/zoo.cfg
vim /usr/local/zookeeper-cluster/zookeeper-2/conf/zoo.cfg clientPort=2182 dataDir=/usr/local/zookeeper-cluster/zookeeper-2/data
修改/usr/local/zookeeper-cluster/zookeeper-3/conf/zoo.cfg
vim /usr/local/zookeeper-cluster/zookeeper-3/conf/zoo.cfg clientPort=2183 dataDir=/usr/local/zookeeper-cluster/zookeeper-3/data
2.3 配置集群 (1)在每个zookeeper的 data 目录下创建一个 myid 文件,内容分别是1、2、3 。这个文件就是记录每个服务器的ID
echo 1 >/usr/local/zookeeper-cluster/zookeeper-1/data/myid echo 2 >/usr/local/zookeeper-cluster/zookeeper-2/data/myid echo 3 >/usr/local/zookeeper-cluster/zookeeper-3/data/myid
(2)在每一个zookeeper 的 zoo.cfg配置客户端访问端口(clientPort)和集群服务器IP列表。
集群服务器IP列表如下
vim /usr/local/zookeeper-cluster/zookeeper-1/conf/zoo.cfg vim /usr/local/zookeeper-cluster/zookeeper-2/conf/zoo.cfg vim /usr/local/zookeeper-cluster/zookeeper-3/conf/zoo.cfg server.1=192.168.149.135:2881:3881 server.2=192.168.149.135:2882:3882 server.3=192.168.149.135:2883:3883
解释:server.服务器ID=服务器IP地址:服务器之间通信端口:服务器之间投票选举端口
2.4 启动集群 启动集群就是分别启动每个实例。
/usr/local/zookeeper-cluster/zookeeper-1/bin/zkServer.sh start /usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh start /usr/local/zookeeper-cluster/zookeeper-3/bin/zkServer.sh start
启动后我们查询一下每个实例的运行状态
/usr/local/zookeeper-cluster/zookeeper-1/bin/zkServer.sh status /usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh status /usr/local/zookeeper-cluster/zookeeper-3/bin/zkServer.sh status
先查询第一个服务,Mode为follower表示是跟随者 (从)
再查询第二个服务,Mode为leader表示是领导者 (主)
查询第三个为跟随者(从)
2.5 模拟集群异常 (1)首先我们先测试如果是从服务器挂掉,会怎么样
把3号服务器停掉,观察1号和2号,发现状态并没有变化
/usr/local/zookeeper-cluster/zookeeper-3/bin/zkServer.sh stop /usr/local/zookeeper-cluster/zookeeper-1/bin/zkServer.sh status /usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh status
由此得出结论,3个节点的集群,从服务器挂掉,集群正常
(2)我们再把1号服务器(从服务器)也停掉,查看2号(主服务器)的状态,发现已经停止运行了。
/usr/local/zookeeper-cluster/zookeeper-1/bin/zkServer.sh stop /usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh status
由此得出结论,3个节点的集群,2个从服务器都挂掉,主服务器也无法运行。因为可运行的机器没有超过集群总数量的半数。
(3)我们再次把1号服务器启动起来,发现2号服务器又开始正常工作了。而且依然是领导者。
/usr/local/zookeeper-cluster/zookeeper-1/bin/zkServer.sh start /usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh status
(4)我们把3号服务器也启动起来,把2号服务器停掉,停掉后观察1号和3号的状态。
/usr/local/zookeeper-cluster/zookeeper-3/bin/zkServer.sh start /usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh stop /usr/local/zookeeper-cluster/zookeeper-1/bin/zkServer.sh status /usr/local/zookeeper-cluster/zookeeper-3/bin/zkServer.sh status
发现新的leader产生了~
由此我们得出结论,当集群中的主服务器挂了,集群中的其他服务器会自动进行选举状态,然后产生新得leader
(5)我们再次测试,当我们把2号服务器重新启动起来启动后,会发生什么?2号服务器会再次成为新的领导吗?我们看结果
/usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh start /usr/local/zookeeper-cluster/zookeeper-2/bin/zkServer.sh status /usr/local/zookeeper-cluster/zookeeper-3/bin/zkServer.sh status
我们会发现,2号服务器启动后依然是跟随者(从服务器),3号服务器依然是领导者(主服务器),没有撼动3号服务器的领导地位。
由此我们得出结论,当领导者产生后,再次有新服务器加入集群,不会影响到现任领导者。
-
三、服务端常用命令
启动ZooKeeper服务:./zkServer.sh start
查看ZooKeeper服务状态:./zkServer.sh status
停止ZooKeeper服务:./zkServer.sh stop
重启ZooKeeper服务:./zkServer.sh restart
四、客户端常用命令
连接ZooKeeper服务端:./zkCli.sh –server ip:port
./zkCli.sh -server localhost:2181
断开连接:quit
查看命令帮助:help
显示指定目录下节点:ls 目录
创建节点:create /节点path value
获取节点值:get /节点path
设置节点值:set /节点path value
删除单个节点:delete /节点path
删除带有子节点的节点:deleteall /节点path
创建临时节点:create -e /节点path value
【退出后节点消失】
创建顺序节点:create -s /节点path value
查询节点详细信息:ls –s /节点path
五、JavaAPI 5.1 安装环境
Curator 是 Apache ZooKeeper 的Java客户端库。
常见的ZooKeeper Java API :
原生Java API
ZkClient
Curator
Curator 项目的目标是简化 ZooKeeper 客户端的使用。
Curator 最初是 Netfix 研发的,后来捐献了 Apache 基金会,目前是 Apache 的顶级项目。
官网:http://curator.apache.org/
5.1.1 方式一:curator-framework 1)pom依赖
<?xml version="1.0" encoding="UTF-8" ?> <project xmlns ="http://maven.apache.org/POM/4.0.0" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation ="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" > <modelVersion > 4.0.0</modelVersion > <groupId > com.itheima</groupId > <artifactId > zk-client</artifactId > <version > 1.0-SNAPSHOT</version > <dependencies > <dependency > <groupId > junit</groupId > <artifactId > junit</artifactId > <version > 4.10</version > <scope > test</scope > </dependency > <dependency > <groupId > org.apache.curator</groupId > <artifactId > curator-framework</artifactId > <version > 4.0.0</version > </dependency > <dependency > <groupId > org.apache.curator</groupId > <artifactId > curator-recipes</artifactId > <version > 4.0.0</version > </dependency > <dependency > <groupId > org.slf4j</groupId > <artifactId > slf4j-api</artifactId > <version > 1.7.21</version > </dependency > <dependency > <groupId > org.slf4j</groupId > <artifactId > slf4j-log4j12</artifactId > <version > 1.7.21</version > </dependency > </dependencies > <build > <plugins > <plugin > <groupId > org.apache.maven.plugins</groupId > <artifactId > maven-compiler-plugin</artifactId > <version > 3.1</version > <configuration > <source > 1.8</source > <target > 1.8</target > </configuration > </plugin > </plugins > </build > </project >
2)log4j.properties
log4j.rootLogger =off,stdout log4j.appender.stdout = org.apache.log4j.ConsoleAppender log4j.appender.stdout.Target = System.out log4j.appender.stdout.layout = org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern = [%d{yyyy-MM-dd HH/:mm/:ss}]%-5p %c(line/:%L) %x-%m%n
5.1.2 方式二:springcloud【暂未测试,应用方式一】 <?xml version="1.0" encoding="UTF-8" ?> <project xmlns ="http://maven.apache.org/POM/4.0.0" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation ="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" > <modelVersion > 4.0.0</modelVersion > <parent > <groupId > org.springframework.boot</groupId > <artifactId > spring-boot-starter-parent</artifactId > <version > 2.7.15</version > <relativePath /> </parent > <groupId > com.example</groupId > <artifactId > zookeeper-demo</artifactId > <version > 0.0.1-SNAPSHOT</version > <name > zookeeper-demo</name > <description > zookeeper-demo</description > <properties > <java.version > 1.8</java.version > <spring-cloud.version > 2021.0.8</spring-cloud.version > </properties > <dependencies > <dependency > <groupId > org.springframework.boot</groupId > <artifactId > spring-boot-starter-web</artifactId > </dependency > <dependency > <groupId > org.springframework.cloud</groupId > <artifactId > spring-cloud-starter-zookeeper-config</artifactId > </dependency > <dependency > <groupId > org.springframework.cloud</groupId > <artifactId > spring-cloud-starter-zookeeper-discovery</artifactId > </dependency > <dependency > <groupId > org.springframework.boot</groupId > <artifactId > spring-boot-starter-test</artifactId > <scope > test</scope > </dependency > </dependencies > <dependencyManagement > <dependencies > <dependency > <groupId > org.springframework.cloud</groupId > <artifactId > spring-cloud-dependencies</artifactId > <version > ${spring-cloud.version}</version > <type > pom</type > <scope > import</scope > </dependency > </dependencies > </dependencyManagement > <build > <plugins > <plugin > <groupId > org.springframework.boot</groupId > <artifactId > spring-boot-maven-plugin</artifactId > </plugin > </plugins > </build > </project >
5.2 API操作
建立连接
添加节点
删除节点
修改节点
查询节点
Watch事件监听
分布式锁实现
5.2.1 建立连接 ① newClient连接 public class CuratorTest { @Test public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); CuratorFramework client = CuratorFrameworkFactory.newClient("192.168.49.11:2181" , 60 * 1000 , 15 * 1000 , retryPolicy); client.start(); } }
② builder连接 public class CuratorTest { @Test public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); CuratorFramework client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } }
5.2.2 添加节点 创建节点: create 持久 临时 顺序 数据
基本创建
创建节点 带有数据
设置节点的类型
创建多级节点 /app1/p1
public class CuratorCreateTest { private CuratorFramework client = null ; @Before public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } @After public void testClose () { if (client != null ) { client.close(); } } @Test public void testCreate1 () throws Exception { String path = client.create().forPath("/app1" ); System.out.println(path); } @Test public void testCreate2 () throws Exception { String path = client.create().forPath("/app2" ,"he" .getBytes(StandardCharsets.UTF_8)); System.out.println(path); } @Test public void testCreate3 () throws Exception { String path = client.create().withMode(CreateMode.EPHEMERAL).forPath("/app3" ); System.out.println(path); Thread.sleep(10000 ); } @Test public void testCreate4 () throws Exception { String path = client.create().creatingParentsIfNeeded().forPath("/app4/p1" ); System.out.println(path); } }
5.2.3 查询节点 查询节点:
插叙年数据:get
查询子节点:ls
查询节点状态信息:ls -s
public class CuratorGetTest { private CuratorFramework client = null ; @Before public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } @After public void testClose () { if (client != null ) { client.close(); } } @Test public void testGet1 () throws Exception { byte [] data = client.getData().forPath("/app1" ); System.out.println(new String (data)); } @Test public void testGet2 () throws Exception { List<String> path = client.getChildren().forPath("/" ); System.out.println(path); } @Test public void testGet3 () throws Exception { Stat stat = new Stat (); System.out.println("stat: " +stat); client.getData().storingStatIn(stat).forPath("/app1" ); System.out.println(stat); } }
5.2.4 修改节点 修改数据
基本修改数据
根据版本修改
public class CuratorSetTest { private CuratorFramework client = null ; @Before public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } @After public void testClose () { if (client != null ) { client.close(); } } @Test public void testSet () throws Exception { client.setData().forPath("/app1" , "bamboo" .getBytes(StandardCharsets.UTF_8)); } @Test public void testSetForVersion () throws Exception { Stat stat = new Stat (); client.getData().storingStatIn(stat).forPath("/app1" ); int version = stat.getVersion(); client.setData().withVersion(version).forPath("/app1" , "bamboo2" .getBytes(StandardCharsets.UTF_8)); } }
5.2.5 删除节点 删除节点
删除单个节点
删除带有子节点的节点
必须成功的删除
回调
public class CuratorDeleteTest { private CuratorFramework client = null ; @Before public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } @After public void testClose () { if (client != null ) { client.close(); } } @Test public void testDelete1 () throws Exception { client.delete().forPath("/app1" ); } @Test public void testDelete2 () throws Exception { client.delete().deletingChildrenIfNeeded().forPath("/app4" ); } @Test public void testDelete3 () throws Exception { client.delete().guaranteed().forPath("/app2" ); } @Test public void testDelete4 () throws Exception { client.delete().guaranteed().inBackground(new BackgroundCallback () { @Override public void processResult (CuratorFramework curatorFramework, CuratorEvent curatorEvent) throws Exception { System.out.println("被删除了" ); System.out.println(curatorEvent); } }).forPath("/app1" ); } }
六、Watch事件监听 ZooKeeper 允许用户在指定节点上注册一些Watcher,并且在一些特定事件触发的时候,ZooKeeper 服务端会将事件通知到感兴趣的客户端上去,该机制是 ZooKeeper 实现分布式协调服务的重要特性。
ZooKeeper 中引入了Watcher机制来实现了发布/订阅功能能,能够让多个订阅者同时监听某一个对象,当一个对象自身状态变化时,会通知所有订阅者。
ZooKeeper 原生支持通过注册Watcher来进行事件监听,但是其使用并不是特别方便,需要开发人员自己反复注册Watcher,比较繁琐。
Curator引入了 Cache 来实现对 ZooKeeper 服务端事件的监听。
ZooKeeper提供了三种Watcher:
NodeCache : 只是监听某一个特定的节点
PathChildrenCache : 监控一个ZNode的子节点.
TreeCache : 可以监控整个树上的所有节点,类似于PathChildrenCache和NodeCache的组合
6.1 NodeCache public class CuratorWatcherTest { private CuratorFramework client = null ; @Before public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } @After public void testClose () { if (client != null ) { client.close(); } } @Test public void testNodeCache () throws Exception { final NodeCache nodeCache = new NodeCache (client, "/app1" ); nodeCache.getListenable().addListener(new NodeCacheListener () { @Override public void nodeChanged () throws Exception { System.out.println("change node" ); byte [] data = nodeCache.getCurrentData().getData(); System.out.println(new String (data)); } }); nodeCache.start(true ); while (true ){ } } }
6.2 PathChildrenCache public class CuratorWatcherTest { private CuratorFramework client = null ; @Before public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } @After public void testClose () { if (client != null ) { client.close(); } } @Test public void testPathChildrenCache () throws Exception { PathChildrenCache pathChildrenCache = new PathChildrenCache (client, "/app2" , true ); pathChildrenCache.getListenable().addListener(new PathChildrenCacheListener () { @Override public void childEvent (CuratorFramework curatorFramework, PathChildrenCacheEvent pathChildrenCacheEvent) throws Exception { System.out.println("子节点变化了" ); System.out.println(pathChildrenCacheEvent); PathChildrenCacheEvent.Type type = pathChildrenCacheEvent.getType(); if (type.equals(PathChildrenCacheEvent.Type.CHILD_UPDATED)) { System.out.println("数据变更" ); byte [] data = pathChildrenCacheEvent.getData().getData(); System.out.println(new String (data)); } } }); pathChildrenCache.start(); while (true ) { } } }
6.3 TreeCache public class CuratorWatcherTest { private CuratorFramework client = null ; @Before public void testConnect () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); } @After public void testClose () { if (client != null ) { client.close(); } } @Test public void testTreeCache () throws Exception { TreeCache treeCache = new TreeCache (client, "/app2" ); treeCache.getListenable().addListener(new TreeCacheListener () { @Override public void childEvent (CuratorFramework curatorFramework, TreeCacheEvent treeCacheEvent) throws Exception { System.out.println("节点变化了" ); System.out.println(treeCacheEvent); } }); treeCache.start(); while (true ) { } } }
七、分布式锁 在我们进行单机应用开发,涉及并发同步的时候,我们往往采用synchronized或者Lock的方式来解决多线程间的代码同步问题,这时多线程的运行都是在同一个JVM之下,没有任何问题。
但当我们的应用是分布式集群工作的情况下,属于多JVM下的工作环境,跨JVM之间已经无法通过多线程的锁解决同步问题。
那么就需要一种更加高级的锁机制,来处理种跨机器的进程之间的数据同步问题 ——这就是分布式锁。
7.1 ZooKeeper分布式锁原理 核心思想:当客户端要获取锁,则创建节点,使用完锁,则删除该节点。
客户端获取锁时,在lock节点下创建临时顺序 节点。
然后获取lock下面的所有子节点,客户端获取到所有的子节点之后,如果发现自己创建的子节点序号最小,那么就认为该客户端获取到了锁。使用完锁后,将该节点删除。
如果发现自己创建的节点并非lock所有子节点中最小的,说明自己还没有获取到锁,此时客户端需要找到比自己小的那个节点,同时对其注册事件监听器,监听删除事件。
如果发现比自己小的那个节点被删除,则客户端的 Watcher会收到相应通知,此时再次判断自己创建的节点是否是lock子节点中序号最小的,如果是则获取到了锁,如果不是则重复以上步骤继续获取到比自己小的一个节点并注册监听。
7.2 Curator实现分布式锁API 在Curator中有五种锁方案:
InterProcessSemaphoreMutex:分布式排它锁(非可重入锁)
InterProcessMutex:分布式可重入排它锁
InterProcessReadWriteLock:分布式读写锁
InterProcessMultiLock:将多个锁作为单个实体管理的容器
InterProcessSemaphoreV2:共享信号量
1)锁实现
package com.bamboo.boot;import org.apache.curator.RetryPolicy;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.framework.recipes.locks.InterProcessMutex;import org.apache.curator.retry.ExponentialBackoffRetry;import java.util.concurrent.TimeUnit;public class Ticket12306 implements Runnable { private int tickets = 10 ; private InterProcessMutex lock; public Ticket12306 () { RetryPolicy retryPolicy = new ExponentialBackoffRetry (3000 , 10 ); CuratorFramework client = CuratorFrameworkFactory.builder().connectString("192.168.49.11:2181" ) .sessionTimeoutMs(60 * 1000 ) .connectionTimeoutMs(15 * 1000 ) .retryPolicy(retryPolicy) .namespace("bamboo" ) .build(); client.start(); this .lock = new InterProcessMutex (client,"/lock" ); } @Override public void run () { while (true ) { try { lock.acquire(3 , TimeUnit.SECONDS); if (tickets > 0 ) { System.out.println(Thread.currentThread() + " : " + tickets); Thread.sleep(100 ); tickets--; } } catch (Exception e) { e.printStackTrace(); }finally { try { lock.release(); } catch (Exception e) { e.printStackTrace(); } } } } }
2)调用锁
public class LockTest { public static void main (String[] args) { Ticket12306 ticket12306 = new Ticket12306 (); Thread t1 = new Thread (ticket12306, "携程" ); Thread t2 = new Thread (ticket12306, "飞猪" ); t1.start(); t2.start(); } }
3)结果
Thread[携程,5 ,main] : 10 java.lang.IllegalMonitorStateException: You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [飞猪,5,main ] : 9java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [携程,5,main ] : 8java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [飞猪,5,main ] : 7java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [携程,5,main ] : 6java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [飞猪,5,main ] : 5java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [携程,5,main ] : 4java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [飞猪,5,main ] : 3java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50) at java.lang.Thread.run (Thread.java :750) Thread [携程,5,main ] : 2Thread [飞猪,5,main ] : 1java.lang.IllegalMonitorStateException : You do not own the lock : /lock at org.apache.curator.framework.recipes.locks.InterProcessMutex.release (InterProcessMutex.java :140) at com.bamboo.boot.Ticket12306.run (Ticket12306.java :50)