Apache Curator Path Cache Watcher

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可以监控某一路径的直接子结点(一级子结点)变化，add,update,delete。

利用此特性可以很方便的监控集群中的所有结点，当然也就很方便的可以实现简单的key.hashCode()%serverCount式的分布式计算，还可以实现简单的定制规则的负载均衡。

1.run ChildrenListener2.run CLTest
package com.collonn.javaUtilMvn.zookeeper.curator.PathCache;public class CLTest {    public static void main(String[] args) throws Exception {        CLClient01.main(null);        CLClient02.main(null);        CLClient03.main(null);    }}


package com.collonn.javaUtilMvn.zookeeper.curator.PathCache;import org.apache.curator.RetryPolicy;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.framework.recipes.cache.ChildData;import org.apache.curator.framework.recipes.cache.PathChildrenCache;import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;import org.apache.curator.retry.ExponentialBackoffRetry;import org.apache.curator.utils.EnsurePath;import java.util.List;public class ChildrenListener {    public static final String C_PATH = "/TestPath";    public static final String CHARSET = "UTF-8";    public static void main(String[] args) {        try {            new Thread(new Runnable() {                @Override                public void run() {                    try{                        String zookeeperConnectionString = "127.0.0.1:2181";                        RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);                        CuratorFramework client = CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy);                        client.start();                        //ensure path of /test                        new EnsurePath(C_PATH).ensure(client.getZookeeperClient());                        final PathChildrenCache pathChildrenCache = new PathChildrenCache(client, C_PATH, true);                        pathChildrenCache.getListenable().addListener(new PathChildrenCacheListener() {                            @Override                            public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception {                                System.out.println("================== catch children change ==================");                                System.out.println("===" + event.getType() + "," + event.getData().getPath() + "," + event.getData().getData());                                List<ChildData> childDataList = pathChildrenCache.getCurrentData();                                if (childDataList != null && childDataList.size() > 0) {                                    System.out.println("===all children as:");                                    for (ChildData childData : childDataList) {                                        System.out.println("==" + childData.getPath() + "," + new String(childData.getData(), "UTF-8"));                                    }                                }                            }                        });                        pathChildrenCache.start();                        Thread.sleep(Integer.MAX_VALUE);                        client.close();                    }catch (Exception e){                        e.printStackTrace();                    }                }            }).start();        }catch (Exception e){            e.printStackTrace();        }    }}


package com.collonn.javaUtilMvn.zookeeper.curator.PathCache;import org.apache.curator.RetryPolicy;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.retry.ExponentialBackoffRetry;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.data.Stat;import java.util.Random;public class CLClient01 {    public static final String C_PATH_SUB = ChildrenListener.C_PATH + "/dog";    public static void main(String[] args) {        new Thread(new Runnable() {            @Override            public void run() {                try {                    String zookeeperConnectionString = "127.0.0.1:2181";                    RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);                    CuratorFramework client = CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy);                    client.start();                    Random random = new Random();                    Thread.sleep(1000 * random.nextInt(3));                    Stat stat = client.checkExists().forPath(C_PATH_SUB);                    if(stat == null){                        client.create().withMode(CreateMode.EPHEMERAL).forPath(C_PATH_SUB, "dogData".getBytes(ChildrenListener.CHARSET));                    }                    Thread.sleep(1000 * random.nextInt(3));                    client.close();                } catch (Exception e) {                    e.printStackTrace();                }            }        }).start();    }}


package com.collonn.javaUtilMvn.zookeeper.curator.PathCache;import org.apache.curator.RetryPolicy;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.retry.ExponentialBackoffRetry;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.data.Stat;import java.nio.charset.Charset;import java.util.Random;public class CLClient02 {    public static final String C_PATH_SUB = ChildrenListener.C_PATH + "/cat";    public static void main(String[] args) {        new Thread(new Runnable() {            @Override            public void run() {                try {                    String zookeeperConnectionString = "127.0.0.1:2181";                    RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);                    CuratorFramework client = CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy);                    client.start();                    Random random = new Random();                    Thread.sleep(1000 * random.nextInt(3));                    Stat stat = client.checkExists().forPath(C_PATH_SUB);                    if(stat == null){                        client.create().withMode(CreateMode.EPHEMERAL).forPath(C_PATH_SUB, "catData".getBytes(Charset.forName(ChildrenListener.CHARSET)));                    }                    Thread.sleep(1000 * random.nextInt(3));                    client.close();                } catch (Exception e) {                    e.printStackTrace();                }            }        }).start();    }}


package com.collonn.javaUtilMvn.zookeeper.curator.PathCache;import org.apache.curator.RetryPolicy;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.retry.ExponentialBackoffRetry;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.data.Stat;import java.nio.charset.Charset;import java.util.Random;public class CLClient03 {    public static final String C_PATH_SUB = ChildrenListener.C_PATH + "/rabbit";    public static void main(String[] args) {        new Thread(new Runnable() {            @Override            public void run() {                try {                    String zookeeperConnectionString = "127.0.0.1:2181";                    RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);                    CuratorFramework client = CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy);                    client.start();                    Random random = new Random();                    Thread.sleep(1000 * random.nextInt(3));                    Stat stat = client.checkExists().forPath(C_PATH_SUB);                    if(stat == null){                        client.create().withMode(CreateMode.EPHEMERAL).forPath(C_PATH_SUB, "rabbitData".getBytes(Charset.forName(ChildrenListener.CHARSET)));                    }                    Thread.sleep(1000 * random.nextInt(3));                    client.close();                } catch (Exception e) {                    e.printStackTrace();                }            }        }).start();    }}

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