zookeeper学习之三(Curator客户端)
2015-06-21 16:16
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Curator框架是最好用,最流行的zookeeper的客户端。
它有以下三个优点
1.提供了一套非常友好的操作API;
2. 提供一些高级特性(包括但不仅限于前篇文章中提到的)的封装
3.易测试
maven依赖如下
Xml代码
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-recipes</artifactId>
<version>2.5.0</version>
</dependency>
按照官方给出的文档和包结构,可以轻松的看出Curator功能分两大类,一是对zookeeper的一些基本命令的封装,比如增删改查。是他的framework模块,一个是他的高级特性,即recipes模块。
一、framework模块
Curator提供了一套Fluent风格的操作API。这在很多脚本类语言里比较流行。
比如他创建client的代码是这样
Java代码
CuratorFramework client = builder.connectString("192.168.11.56:2180") .sessionTimeoutMs(30000) .connectionTimeoutMs(30000) .canBeReadOnly(false) .retryPolicy(new ExponentialBackoffRetry(1000, Integer.MAX_VALUE)) .namespace(namespace) .defaultData(null) .build(); client.start();
一路点到底,这就是所谓的Fluent风格。
我们再看增删改查的
Java代码
public class CrudExamples {
private static CuratorFramework client = ClientFactory.newClient();
private static final String PATH = "/crud";
public static void main(String[] args) {
try {
client.start();
client.create().forPath(PATH, "I love messi".getBytes());
byte[] bs = client.getData().forPath(PATH);
System.out.println("新建的节点,data为:" + new String(bs));
client.setData().forPath(PATH, "I love football".getBytes());
// 由于是在background模式下获取的data,此时的bs可能为null
byte[] bs2 = client.getData().watched().inBackground().forPath(PATH);
System.out.println("修改后的data为" + new String(bs2 != null ? bs2 : new byte[0]));
client.delete().forPath(PATH);
Stat stat = client.checkExists().forPath(PATH);
// Stat就是对zonde所有属性的一个映射, stat=null表示节点不存在!
System.out.println(stat);
} catch (Exception e) {
e.printStackTrace();
} finally {
CloseableUtils.closeQuietly(client);
}
}
}
常用接口有
create()增
delete(): 删
checkExists(): 判断是否存在
setData(): 改
getData(): 查
所有这些方法都以forpath()结尾,辅以watch(监听),withMode(指定模式),和inBackground(后台运行)等方法来使用。
此外,Curator还支持事务,一组crud操作同生同灭。代码如下
Java代码
/**
* 事务操作
*
* @author shencl
*/
public class TransactionExamples {
private static CuratorFramework client = ClientFactory.newClient();
public static void main(String[] args) {
try {
client.start();
// 开启事务
CuratorTransaction transaction = client.inTransaction();
Collection<CuratorTransactionResult> results = transaction.create()
.forPath("/a/path", "some data".getBytes()).and().setData()
.forPath("/another/path", "other data".getBytes()).and().delete().forPath("/yet/another/path")
.and().commit();
for (CuratorTransactionResult result : results) {
System.out.println(result.getForPath() + " - " + result.getType());
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 释放客户端连接
CloseableUtils.closeQuietly(client);
}
}
}
这段的代码的运行结果,由于最后一步delete的节点不存在,所以整个事务commit失败。失败的原因会放在Collection<CuratorTransactionResult>中,非常友好。
好了framework部分的内容就这么多,是不是特别简单呢。下面就来看看recipes包的内容吧。。
Recipes部分提供的功能官网列的很详细,点击这里。注意文章第一段:Curator宣称,Recipes模块实现了除二阶段提交之外的所有zookeeper特性。
二、Recipes模块
主要有
Elections(选举),Locks(锁),Barriers(关卡),Atomic(原子量),Caches,Queues等
1、 Elections
选举主要依赖于LeaderSelector和LeaderLatch2个类。前者是所有存活的客户端不间断的轮流做Leader,大同社会。后者是一旦选举出Leader,除非有客户端挂掉重新触发选举,否则不会交出领导权。某党?
这两者在实现上是可以切换的,直接上代码,怎么切换注释里有。由于篇幅所限,这里仅贴出基于LeaderSelector的选举,更多代码见附件
Java代码
/**
* 本类基于leaderSelector实现,所有存活的client会公平的轮流做leader
* 如果不想频繁的变化Leader,需要在takeLeadership方法里阻塞leader的变更! 或者使用 {@link}
* LeaderLatchClient
*/
public class LeaderSelectorClient extends LeaderSelectorListenerAdapter implements Closeable {
private final String name;
private final LeaderSelector leaderSelector;
private final String PATH = "/leaderselector";
public LeaderSelectorClient(CuratorFramework client, String name) {
this.name = name;
leaderSelector = new LeaderSelector(client, PATH, this);
leaderSelector.autoRequeue();
}
public void start() throws IOException {
leaderSelector.start();
}
@Override
public void close() throws IOException {
leaderSelector.close();
}
/**
* client成为leader后,会调用此方法
*/
@Override
public void takeLeadership(CuratorFramework client) throws Exception {
int waitSeconds = (int) (5 * Math.random()) + 1;
System.out.println(name + "是当前的leader");
try {
Thread.sleep(TimeUnit.SECONDS.toMillis(waitSeconds));
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
System.out.println(name + " 让出领导权\n");
}
}
Java代码
/**
* leader选举
*
* @author shencl
*/
public class LeaderSelectorExample {
public static void main(String[] args) {
List<CuratorFramework> clients = Lists.newArrayList();
List<LeaderSelectorClient> examples = Lists.newArrayList();
try {
for (int i = 0; i < 10; i++) {
CuratorFramework client = ClientFactory.newClient();
LeaderSelectorClient example = new LeaderSelectorClient(client, "Client #" + i);
clients.add(client);
examples.add(example);
client.start();
example.start();
}
System.out.println("----------先观察一会选举的结果-----------");
Thread.sleep(10000);
System.out.println("----------关闭前5个客户端,再观察选举的结果-----------");
for (int i = 0; i < 5; i++) {
clients.get(i).close();
}
// 这里有个小技巧,让main程序一直监听控制台输入,异步的代码就可以一直在执行。不同于while(ture)的是,按回车或esc可退出
new BufferedReader(new InputStreamReader(System.in)).readLine();
} catch (Exception e) {
e.printStackTrace();
} finally {
for (LeaderSelectorClient exampleClient : examples) {
CloseableUtils.closeQuietly(exampleClient);
}
for (CuratorFramework client : clients) {
CloseableUtils.closeQuietly(client);
}
}
}
}
2、locks
curator lock相关的实现在recipes.locks包里。顶级接口都是InterProcessLock。我们直接看最有代表性的InterProcessReadWriteLock 进程内部读写锁(可重入读写锁)。什么叫可重入,什么叫读写锁。不清楚的先查好资料吧。总之读写锁一定是成对出现的。
简易传送门
我们先定义两个任务,可并行的执行的,和互斥执行的。
Java代码
/**
* 并行任务
*
* @author shencl
*/
public class ParallelJob implements Runnable {
private final String name;
private final InterProcessLock lock;
// 锁等待时间
private final int wait_time = 5;
ParallelJob(String name, InterProcessLock lock) {
this.name = name;
this.lock = lock;
}
@Override
public void run() {
try {
doWork();
} catch (Exception e) {
// ingore;
}
}
public void doWork() throws Exception {
try {
if (!lock.acquire(wait_time, TimeUnit.SECONDS)) {
System.err.println(name + "等待" + wait_time + "秒,仍未能获取到lock,准备放弃。");
}
// 模拟job执行时间0-4000毫秒
int exeTime = new Random().nextInt(4000);
System.out.println(name + "开始执行,预计执行时间= " + exeTime + "毫秒----------");
Thread.sleep(exeTime);
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.release();
}
}
}
Java代码
/**
* 互斥任务
*
* @author shencl
*/
public class MutexJob implements Runnable {
private final String name;
private final InterProcessLock lock;
// 锁等待时间
private final int wait_time = 10;
MutexJob(String name, InterProcessLock lock) {
this.name = name;
this.lock = lock;
}
@Override
public void run() {
try {
doWork();
} catch (Exception e) {
// ingore;
}
}
public void doWork() throws Exception {
try {
if (!lock.acquire(wait_time, TimeUnit.SECONDS)) {
System.err.println(name + "等待" + wait_time + "秒,仍未能获取到lock,准备放弃。");
}
// 模拟job执行时间0-2000毫秒
int exeTime = new Random().nextInt(2000);
System.out.println(name + "开始执行,预计执行时间= " + exeTime + "毫秒----------");
Thread.sleep(exeTime);
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.release();
}
}
}
锁测试代码
Java代码
/**
* 分布式锁实例
*
* @author shencl
*/
public class DistributedLockExample {
private static CuratorFramework client = ClientFactory.newClient();
private static final String PATH = "/locks";
// 进程内部(可重入)读写锁
private static final InterProcessReadWriteLock lock;
// 读锁
private static final InterProcessLock readLock;
// 写锁
private static final InterProcessLock writeLock;
static {
client.start();
lock = new InterProcessReadWriteLock(client, PATH);
readLock = lock.readLock();
writeLock = lock.writeLock();
}
public static void main(String[] args) {
try {
List<Thread> jobs = Lists.newArrayList();
for (int i = 0; i < 10; i++) {
Thread t = new Thread(new ParallelJob("Parallel任务" + i, readLock));
jobs.add(t);
}
for (int i = 0; i < 10; i++) {
Thread t = new Thread(new MutexJob("Mutex任务" + i, writeLock));
jobs.add(t);
}
for (Thread t : jobs) {
t.start();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
CloseableUtils.closeQuietly(client);
}
}
}
看到没,用法和java concurrent包里的ReentrantReadWriteLock 是一模一样的。
事实上,整个recipes包的目录结构、实现原理同java concurrent包的设置是很一致的。比如有queue,Semaphore,Barrier等类,。他整个就是模仿jdk的实现,只不过是基于分布式的!
后边的几项,Barriers(关卡),Atomic(原子量),Caches,Queues和java concurrent包里的类的用法是一样的,就不继续贴了,有些附件里有。
要说明的是:有的功能性能不是特别理想,网上也没见有大的项目的使用案例。比如基于CAS机制的atomic,在某些情况重试的效率还不如硬同步,要是zookeeper节点再一多,各个节点之间通过event触发的数据同步极其频繁。那性能可以想象。
三、测试方法
curator提供了很好的测试工具,你甚至是可以在完全没有搭建zookeeper server端的情况下,完成测试。
有2个重要的类
TestingServer 模拟单点, TestingCluster模拟集群。
需要使用的话,得依赖
Xml代码
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-test</artifactId>
<version>2.5.0</version>
</dependency>
全文完。
本文参考:
http://curator.apache.org/ http://www.cnblogs.com/hzhuxin/archive/2012/11/01/2749341.html http://www.chengxuyuans.com/Java+/72042.html http://macrochen.iteye.com/blog/1366136
它有以下三个优点
1.提供了一套非常友好的操作API;
2. 提供一些高级特性(包括但不仅限于前篇文章中提到的)的封装
3.易测试
maven依赖如下
Xml代码
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-recipes</artifactId>
<version>2.5.0</version>
</dependency>
<dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-recipes</artifactId> <version>2.5.0</version> </dependency>
按照官方给出的文档和包结构,可以轻松的看出Curator功能分两大类,一是对zookeeper的一些基本命令的封装,比如增删改查。是他的framework模块,一个是他的高级特性,即recipes模块。
一、framework模块
Curator提供了一套Fluent风格的操作API。这在很多脚本类语言里比较流行。
比如他创建client的代码是这样
Java代码
CuratorFramework client = builder.connectString("192.168.11.56:2180") .sessionTimeoutMs(30000) .connectionTimeoutMs(30000) .canBeReadOnly(false) .retryPolicy(new ExponentialBackoffRetry(1000, Integer.MAX_VALUE)) .namespace(namespace) .defaultData(null) .build(); client.start();
CuratorFramework client = builder.connectString("192.168.11.56:2180") .sessionTimeoutMs(30000) .connectionTimeoutMs(30000) .canBeReadOnly(false) .retryPolicy(new ExponentialBackoffRetry(1000, Integer.MAX_VALUE)) .namespace(namespace) .defaultData(null) .build(); client.start();
一路点到底,这就是所谓的Fluent风格。
我们再看增删改查的
Java代码
public class CrudExamples {
private static CuratorFramework client = ClientFactory.newClient();
private static final String PATH = "/crud";
public static void main(String[] args) {
try {
client.start();
client.create().forPath(PATH, "I love messi".getBytes());
byte[] bs = client.getData().forPath(PATH);
System.out.println("新建的节点,data为:" + new String(bs));
client.setData().forPath(PATH, "I love football".getBytes());
// 由于是在background模式下获取的data,此时的bs可能为null
byte[] bs2 = client.getData().watched().inBackground().forPath(PATH);
System.out.println("修改后的data为" + new String(bs2 != null ? bs2 : new byte[0]));
client.delete().forPath(PATH);
Stat stat = client.checkExists().forPath(PATH);
// Stat就是对zonde所有属性的一个映射, stat=null表示节点不存在!
System.out.println(stat);
} catch (Exception e) {
e.printStackTrace();
} finally {
CloseableUtils.closeQuietly(client);
}
}
}
public class CrudExamples { private static CuratorFramework client = ClientFactory.newClient(); private static final String PATH = "/crud"; public static void main(String[] args) { try { client.start(); client.create().forPath(PATH, "I love messi".getBytes()); byte[] bs = client.getData().forPath(PATH); System.out.println("新建的节点,data为:" + new String(bs)); client.setData().forPath(PATH, "I love football".getBytes()); // 由于是在background模式下获取的data,此时的bs可能为null byte[] bs2 = client.getData().watched().inBackground().forPath(PATH); System.out.println("修改后的data为" + new String(bs2 != null ? bs2 : new byte[0])); client.delete().forPath(PATH); Stat stat = client.checkExists().forPath(PATH); // Stat就是对zonde所有属性的一个映射, stat=null表示节点不存在! System.out.println(stat); } catch (Exception e) { e.printStackTrace(); } finally { CloseableUtils.closeQuietly(client); } } }
常用接口有
create()增
delete(): 删
checkExists(): 判断是否存在
setData(): 改
getData(): 查
所有这些方法都以forpath()结尾,辅以watch(监听),withMode(指定模式),和inBackground(后台运行)等方法来使用。
此外,Curator还支持事务,一组crud操作同生同灭。代码如下
Java代码
/**
* 事务操作
*
* @author shencl
*/
public class TransactionExamples {
private static CuratorFramework client = ClientFactory.newClient();
public static void main(String[] args) {
try {
client.start();
// 开启事务
CuratorTransaction transaction = client.inTransaction();
Collection<CuratorTransactionResult> results = transaction.create()
.forPath("/a/path", "some data".getBytes()).and().setData()
.forPath("/another/path", "other data".getBytes()).and().delete().forPath("/yet/another/path")
.and().commit();
for (CuratorTransactionResult result : results) {
System.out.println(result.getForPath() + " - " + result.getType());
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 释放客户端连接
CloseableUtils.closeQuietly(client);
}
}
}
/** * 事务操作 * * @author shencl */ public class TransactionExamples { private static CuratorFramework client = ClientFactory.newClient(); public static void main(String[] args) { try { client.start(); // 开启事务 CuratorTransaction transaction = client.inTransaction(); Collection<CuratorTransactionResult> results = transaction.create() .forPath("/a/path", "some data".getBytes()).and().setData() .forPath("/another/path", "other data".getBytes()).and().delete().forPath("/yet/another/path") .and().commit(); for (CuratorTransactionResult result : results) { System.out.println(result.getForPath() + " - " + result.getType()); } } catch (Exception e) { e.printStackTrace(); } finally { // 释放客户端连接 CloseableUtils.closeQuietly(client); } } }
这段的代码的运行结果,由于最后一步delete的节点不存在,所以整个事务commit失败。失败的原因会放在Collection<CuratorTransactionResult>中,非常友好。
好了framework部分的内容就这么多,是不是特别简单呢。下面就来看看recipes包的内容吧。。
Recipes部分提供的功能官网列的很详细,点击这里。注意文章第一段:Curator宣称,Recipes模块实现了除二阶段提交之外的所有zookeeper特性。
二、Recipes模块
主要有
Elections(选举),Locks(锁),Barriers(关卡),Atomic(原子量),Caches,Queues等
1、 Elections
选举主要依赖于LeaderSelector和LeaderLatch2个类。前者是所有存活的客户端不间断的轮流做Leader,大同社会。后者是一旦选举出Leader,除非有客户端挂掉重新触发选举,否则不会交出领导权。某党?
这两者在实现上是可以切换的,直接上代码,怎么切换注释里有。由于篇幅所限,这里仅贴出基于LeaderSelector的选举,更多代码见附件
Java代码
/**
* 本类基于leaderSelector实现,所有存活的client会公平的轮流做leader
* 如果不想频繁的变化Leader,需要在takeLeadership方法里阻塞leader的变更! 或者使用 {@link}
* LeaderLatchClient
*/
public class LeaderSelectorClient extends LeaderSelectorListenerAdapter implements Closeable {
private final String name;
private final LeaderSelector leaderSelector;
private final String PATH = "/leaderselector";
public LeaderSelectorClient(CuratorFramework client, String name) {
this.name = name;
leaderSelector = new LeaderSelector(client, PATH, this);
leaderSelector.autoRequeue();
}
public void start() throws IOException {
leaderSelector.start();
}
@Override
public void close() throws IOException {
leaderSelector.close();
}
/**
* client成为leader后,会调用此方法
*/
@Override
public void takeLeadership(CuratorFramework client) throws Exception {
int waitSeconds = (int) (5 * Math.random()) + 1;
System.out.println(name + "是当前的leader");
try {
Thread.sleep(TimeUnit.SECONDS.toMillis(waitSeconds));
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
System.out.println(name + " 让出领导权\n");
}
}
/** * 本类基于leaderSelector实现,所有存活的client会公平的轮流做leader * 如果不想频繁的变化Leader,需要在takeLeadership方法里阻塞leader的变更! 或者使用 {@link} * LeaderLatchClient */ public class LeaderSelectorClient extends LeaderSelectorListenerAdapter implements Closeable { private final String name; private final LeaderSelector leaderSelector; private final String PATH = "/leaderselector"; public LeaderSelectorClient(CuratorFramework client, String name) { this.name = name; leaderSelector = new LeaderSelector(client, PATH, this); leaderSelector.autoRequeue(); } public void start() throws IOException { leaderSelector.start(); } @Override public void close() throws IOException { leaderSelector.close(); } /** * client成为leader后,会调用此方法 */ @Override public void takeLeadership(CuratorFramework client) throws Exception { int waitSeconds = (int) (5 * Math.random()) + 1; System.out.println(name + "是当前的leader"); try { Thread.sleep(TimeUnit.SECONDS.toMillis(waitSeconds)); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { System.out.println(name + " 让出领导权\n"); } }
Java代码
/**
* leader选举
*
* @author shencl
*/
public class LeaderSelectorExample {
public static void main(String[] args) {
List<CuratorFramework> clients = Lists.newArrayList();
List<LeaderSelectorClient> examples = Lists.newArrayList();
try {
for (int i = 0; i < 10; i++) {
CuratorFramework client = ClientFactory.newClient();
LeaderSelectorClient example = new LeaderSelectorClient(client, "Client #" + i);
clients.add(client);
examples.add(example);
client.start();
example.start();
}
System.out.println("----------先观察一会选举的结果-----------");
Thread.sleep(10000);
System.out.println("----------关闭前5个客户端,再观察选举的结果-----------");
for (int i = 0; i < 5; i++) {
clients.get(i).close();
}
// 这里有个小技巧,让main程序一直监听控制台输入,异步的代码就可以一直在执行。不同于while(ture)的是,按回车或esc可退出
new BufferedReader(new InputStreamReader(System.in)).readLine();
} catch (Exception e) {
e.printStackTrace();
} finally {
for (LeaderSelectorClient exampleClient : examples) {
CloseableUtils.closeQuietly(exampleClient);
}
for (CuratorFramework client : clients) {
CloseableUtils.closeQuietly(client);
}
}
}
}
/** * leader选举 * * @author shencl */ public class LeaderSelectorExample { public static void main(String[] args) { List<CuratorFramework> clients = Lists.newArrayList(); List<LeaderSelectorClient> examples = Lists.newArrayList(); try { for (int i = 0; i < 10; i++) { CuratorFramework client = ClientFactory.newClient(); LeaderSelectorClient example = new LeaderSelectorClient(client, "Client #" + i); clients.add(client); examples.add(example); client.start(); example.start(); } System.out.println("----------先观察一会选举的结果-----------"); Thread.sleep(10000); System.out.println("----------关闭前5个客户端,再观察选举的结果-----------"); for (int i = 0; i < 5; i++) { clients.get(i).close(); } // 这里有个小技巧,让main程序一直监听控制台输入,异步的代码就可以一直在执行。不同于while(ture)的是,按回车或esc可退出 new BufferedReader(new InputStreamReader(System.in)).readLine(); } catch (Exception e) { e.printStackTrace(); } finally { for (LeaderSelectorClient exampleClient : examples) { CloseableUtils.closeQuietly(exampleClient); } for (CuratorFramework client : clients) { CloseableUtils.closeQuietly(client); } } } }
2、locks
curator lock相关的实现在recipes.locks包里。顶级接口都是InterProcessLock。我们直接看最有代表性的InterProcessReadWriteLock 进程内部读写锁(可重入读写锁)。什么叫可重入,什么叫读写锁。不清楚的先查好资料吧。总之读写锁一定是成对出现的。
简易传送门
我们先定义两个任务,可并行的执行的,和互斥执行的。
Java代码
/**
* 并行任务
*
* @author shencl
*/
public class ParallelJob implements Runnable {
private final String name;
private final InterProcessLock lock;
// 锁等待时间
private final int wait_time = 5;
ParallelJob(String name, InterProcessLock lock) {
this.name = name;
this.lock = lock;
}
@Override
public void run() {
try {
doWork();
} catch (Exception e) {
// ingore;
}
}
public void doWork() throws Exception {
try {
if (!lock.acquire(wait_time, TimeUnit.SECONDS)) {
System.err.println(name + "等待" + wait_time + "秒,仍未能获取到lock,准备放弃。");
}
// 模拟job执行时间0-4000毫秒
int exeTime = new Random().nextInt(4000);
System.out.println(name + "开始执行,预计执行时间= " + exeTime + "毫秒----------");
Thread.sleep(exeTime);
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.release();
}
}
}
/** * 并行任务 * * @author shencl */ public class ParallelJob implements Runnable { private final String name; private final InterProcessLock lock; // 锁等待时间 private final int wait_time = 5; ParallelJob(String name, InterProcessLock lock) { this.name = name; this.lock = lock; } @Override public void run() { try { doWork(); } catch (Exception e) { // ingore; } } public void doWork() throws Exception { try { if (!lock.acquire(wait_time, TimeUnit.SECONDS)) { System.err.println(name + "等待" + wait_time + "秒,仍未能获取到lock,准备放弃。"); } // 模拟job执行时间0-4000毫秒 int exeTime = new Random().nextInt(4000); System.out.println(name + "开始执行,预计执行时间= " + exeTime + "毫秒----------"); Thread.sleep(exeTime); } catch (Exception e) { e.printStackTrace(); } finally { lock.release(); } } }
Java代码
/**
* 互斥任务
*
* @author shencl
*/
public class MutexJob implements Runnable {
private final String name;
private final InterProcessLock lock;
// 锁等待时间
private final int wait_time = 10;
MutexJob(String name, InterProcessLock lock) {
this.name = name;
this.lock = lock;
}
@Override
public void run() {
try {
doWork();
} catch (Exception e) {
// ingore;
}
}
public void doWork() throws Exception {
try {
if (!lock.acquire(wait_time, TimeUnit.SECONDS)) {
System.err.println(name + "等待" + wait_time + "秒,仍未能获取到lock,准备放弃。");
}
// 模拟job执行时间0-2000毫秒
int exeTime = new Random().nextInt(2000);
System.out.println(name + "开始执行,预计执行时间= " + exeTime + "毫秒----------");
Thread.sleep(exeTime);
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.release();
}
}
}
/** * 互斥任务 * * @author shencl */ public class MutexJob implements Runnable { private final String name; private final InterProcessLock lock; // 锁等待时间 private final int wait_time = 10; MutexJob(String name, InterProcessLock lock) { this.name = name; this.lock = lock; } @Override public void run() { try { doWork(); } catch (Exception e) { // ingore; } } public void doWork() throws Exception { try { if (!lock.acquire(wait_time, TimeUnit.SECONDS)) { System.err.println(name + "等待" + wait_time + "秒,仍未能获取到lock,准备放弃。"); } // 模拟job执行时间0-2000毫秒 int exeTime = new Random().nextInt(2000); System.out.println(name + "开始执行,预计执行时间= " + exeTime + "毫秒----------"); Thread.sleep(exeTime); } catch (Exception e) { e.printStackTrace(); } finally { lock.release(); } } }
锁测试代码
Java代码
/**
* 分布式锁实例
*
* @author shencl
*/
public class DistributedLockExample {
private static CuratorFramework client = ClientFactory.newClient();
private static final String PATH = "/locks";
// 进程内部(可重入)读写锁
private static final InterProcessReadWriteLock lock;
// 读锁
private static final InterProcessLock readLock;
// 写锁
private static final InterProcessLock writeLock;
static {
client.start();
lock = new InterProcessReadWriteLock(client, PATH);
readLock = lock.readLock();
writeLock = lock.writeLock();
}
public static void main(String[] args) {
try {
List<Thread> jobs = Lists.newArrayList();
for (int i = 0; i < 10; i++) {
Thread t = new Thread(new ParallelJob("Parallel任务" + i, readLock));
jobs.add(t);
}
for (int i = 0; i < 10; i++) {
Thread t = new Thread(new MutexJob("Mutex任务" + i, writeLock));
jobs.add(t);
}
for (Thread t : jobs) {
t.start();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
CloseableUtils.closeQuietly(client);
}
}
}
/** * 分布式锁实例 * * @author shencl */ public class DistributedLockExample { private static CuratorFramework client = ClientFactory.newClient(); private static final String PATH = "/locks"; // 进程内部(可重入)读写锁 private static final InterProcessReadWriteLock lock; // 读锁 private static final InterProcessLock readLock; // 写锁 private static final InterProcessLock writeLock; static { client.start(); lock = new InterProcessReadWriteLock(client, PATH); readLock = lock.readLock(); writeLock = lock.writeLock(); } public static void main(String[] args) { try { List<Thread> jobs = Lists.newArrayList(); for (int i = 0; i < 10; i++) { Thread t = new Thread(new ParallelJob("Parallel任务" + i, readLock)); jobs.add(t); } for (int i = 0; i < 10; i++) { Thread t = new Thread(new MutexJob("Mutex任务" + i, writeLock)); jobs.add(t); } for (Thread t : jobs) { t.start(); } } catch (Exception e) { e.printStackTrace(); } finally { CloseableUtils.closeQuietly(client); } } }
看到没,用法和java concurrent包里的ReentrantReadWriteLock 是一模一样的。
事实上,整个recipes包的目录结构、实现原理同java concurrent包的设置是很一致的。比如有queue,Semaphore,Barrier等类,。他整个就是模仿jdk的实现,只不过是基于分布式的!
后边的几项,Barriers(关卡),Atomic(原子量),Caches,Queues和java concurrent包里的类的用法是一样的,就不继续贴了,有些附件里有。
要说明的是:有的功能性能不是特别理想,网上也没见有大的项目的使用案例。比如基于CAS机制的atomic,在某些情况重试的效率还不如硬同步,要是zookeeper节点再一多,各个节点之间通过event触发的数据同步极其频繁。那性能可以想象。
三、测试方法
curator提供了很好的测试工具,你甚至是可以在完全没有搭建zookeeper server端的情况下,完成测试。
有2个重要的类
TestingServer 模拟单点, TestingCluster模拟集群。
需要使用的话,得依赖
Xml代码
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-test</artifactId>
<version>2.5.0</version>
</dependency>
<dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-test</artifactId> <version>2.5.0</version> </dependency>
全文完。
本文参考:
http://curator.apache.org/ http://www.cnblogs.com/hzhuxin/archive/2012/11/01/2749341.html http://www.chengxuyuans.com/Java+/72042.html http://macrochen.iteye.com/blog/1366136
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