zookeeper curator学习（增删改查）（1）

主要参考的是curator，github地址：https://github.com/apache/curator/tree/master/curator-examples。

zookeeper版本为zookeeper-3.4.9（需要查找合适的curator版本）

源码地址：https://gitee.com/zhangjunqing/spring-boot/tree/master/zookeeper

curator的优势介绍：http://www.cnblogs.com/LiZhiW/p/4923693.html

（1）pom文件如下

<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.zookeeper</groupId>
  <artifactId>zookeeper</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>zookeeper</name>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

 <dependencies>
     <dependency>
            <groupId>org.apache.curator</groupId>
            <artifactId>curator-recipes</artifactId>
            <version>2.7.0</version>
        </dependency>

        <dependency>
            <groupId>org.apache.curator</groupId>
            <artifactId>curator-test</artifactId>
            <version>2.7.0</version>
        </dependency>

        <dependency>
            <groupId>org.apache.curator</groupId>
            <artifactId>curator-x-discovery</artifactId>
            <version>2.7.0</version>
        </dependency>
        
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.2</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.25</version>
            <scope>test</scope>
        </dependency>
 </dependencies>

</project>

（2）使用curator链接zookeeper程序如下：

package com.topsec.framework;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;

public class CreateClientExamples
{
    
    //创建简单的 CuratorFramework
    public static CuratorFramework createSimple(String connectionString)
    {
        // these are reasonable arguments for the ExponentialBackoffRetry. The first
        // retry will wait 1 second - the second will wait up to 2 seconds - the
        // third will wait up to 4 seconds.
        ExponentialBackoffRetry retryPolicy = new ExponentialBackoffRetry(1000, 3);

        // The simplest way to get a CuratorFramework instance. This will use default values.
        // The only required arguments are the connection string and the retry policy
        return CuratorFrameworkFactory.newClient(connectionString, retryPolicy);
    }

    //创建复杂的CuratorFramework
    public static CuratorFramework  createWithOptions(String connectionString, RetryPolicy retryPolicy, int connectionTimeoutMs, int sessionTimeoutMs)
    {
        // using the CuratorFrameworkFactory.builder() gives fine grained control
        // over creation options. See the CuratorFrameworkFactory.Builder javadoc
        // details
        return CuratorFrameworkFactory.builder()
            .connectString(connectionString)
            .retryPolicy(retryPolicy)
            .connectionTimeoutMs(connectionTimeoutMs)
            .sessionTimeoutMs(sessionTimeoutMs)
            // etc. etc.
            .build();
    }
}

（3）进行节点增删改查的示例代码

package com.topsec.framework;

import java.util.List;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorEvent;
import org.apache.curator.framework.api.CuratorListener;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.Watcher;

public class CrudExamples
{
    public static void      create(CuratorFramework client, String path, byte[] payload) throws Exception
    {
        // this will create the given ZNode with the given data
        client.create().forPath(path, payload);
    }

    public static void      createEphemeral(CuratorFramework client, String path, byte[] payload) throws Exception
    {
        // this will create the given EPHEMERAL ZNode with the given data
        client.create().withMode(CreateMode.EPHEMERAL).forPath(path, payload);
    }

    public static String    createEphemeralSequential(CuratorFramework client, String path, byte[] payload) throws Exception
    {
        // this will create the given EPHEMERAL-SEQUENTIAL ZNode with the given data using Curator protection.

        /*
            Protection Mode:
            It turns out there is an edge case that exists when creating sequential-ephemeral nodes. The creation
            can succeed on the server, but the server can crash before the created node name is returned to the
            client. However, the ZK session is still valid so the ephemeral node is not deleted. Thus, there is no
            way for the client to determine what node was created for them.
            Even without sequential-ephemeral, however, the create can succeed on the sever but the client (for various
            reasons) will not know it. Putting the create builder into protection mode works around this. The name of
            the node that is created is prefixed with a GUID. If node creation fails the normal retry mechanism will
            occur. On the retry, the parent path is first searched for a node that has the GUID in it. If that node is
            found, it is assumed to be the lost node that was successfully created on the first try and is returned to
            the caller.
         */
        return client.create().withProtection().withMode(CreateMode.EPHEMERAL_SEQUENTIAL).forPath(path, payload);
    }

    public static void      setData(CuratorFramework client, String path, byte[] payload) throws Exception
    {
        // set data for the given node
        client.setData().forPath(path, payload);
    }

    public static void      setDataAsync(CuratorFramework client, String path, byte[] payload) throws Exception
    {
        // this is one method of getting event/async notifications
        CuratorListener listener = new CuratorListener()
        {
            public void eventReceived(CuratorFramework client, CuratorEvent event) throws Exception
            {
                // examine event for details
                System.out.println("返回事件" + event.getWatchedEvent());
            }
        };
        client.getCuratorListenable().addListener(listener);

        // set data for the given node asynchronously. The completion notification
        // is done via the CuratorListener.
        client.setData().inBackground().forPath(path, payload);
    }

    public static void      setDataAsyncWithCallback(CuratorFramework client, BackgroundCallback callback, String path, byte[] payload) throws Exception
    {
        // this is another method of getting notification of an async completion
        client.setData().inBackground(callback).forPath(path, payload);
    }

    public static void      delete(CuratorFramework client, String path) throws Exception
    {
        // delete the given node
        client.delete().forPath(path);
    }

    public static void      guaranteedDelete(CuratorFramework client, String path) throws Exception
    {
        // delete the given node and guarantee that it completes

        /*
            Guaranteed Delete
            Solves this edge case: deleting a node can fail due to connection issues. Further, if the node was
            ephemeral, the node will not get auto-deleted as the session is still valid. This can wreak havoc
            with lock implementations.
            When guaranteed is set, Curator will record failed node deletions and attempt to delete them in the
            background until successful. NOTE: you will still get an exception when the deletion fails. But, you
            can be assured that as long as the CuratorFramework instance is open attempts will be made to delete
            the node.
         */

        client.delete().guaranteed().forPath(path);
    }

    public static List<String> watchedGetChildren(CuratorFramework client, String path) throws Exception
    {
        /**
         * Get children and set a watcher on the node. The watcher notification will come through the
         * CuratorListener (see setDataAsync() above).
         */
        return client.getChildren().watched().forPath(path);
    }

    public static List<String> watchedGetChildren(CuratorFramework client, String path, Watcher watcher) throws Exception
    {
        /**
         * Get children and set the given watcher on the node.
         */
        return client.getChildren().usingWatcher(watcher).forPath(path);
    }
}

（4）测试程序：

package com.topsec.framework;

import org.apache.curator.framework.CuratorFramework;

public class FrameworkTest {
    //zookeeper集群
    public static final String ZOOKEEPERSTRING = "192.168.99.129:2181,192.168.99.153:2181,192.168.99.171:2181";
    
    public static void main(String args[]) {
        CuratorFramework  curatorFramework = null;
        try {
            curatorFramework = CreateClientExamples.createSimple(ZOOKEEPERSTRING);
            curatorFramework.start();
            //创建节点  只能在存在的节点下创建,并且该节点必须不存在
//            CrudExamples.create(curatorFramework, "/zookeeperTest/number2", "test1".getBytes());
        
            //创建临时节点
            //CrudExamples.createEphemeral(curatorFramework, "/zookeeperTest/tempNode", "tempNode".getBytes());
            
            //创建临时顺序节点
            //CrudExamples.createEphemeralSequential(curatorFramework, "/zookeeperTest/tempSeqNode", "tempSeqNode".getBytes());
            
            //修改节点
            //CrudExamples.setData(curatorFramework, "/zookeeperTest/number2", "number2".getBytes());
            
            //异步设置数据
            //CrudExamples.setDataAsync(curatorFramework, "/zookeeperTest/number2", "number3".getBytes());
            
            
            //删除节点
            //CrudExamples.delete(curatorFramework, "/zookeeperTest/number2");
            
            //安全保证删除
            CrudExamples.guaranteedDelete(curatorFramework, "/zookeeperTest/number2"); 
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if(curatorFramework!=null) {
                curatorFramework.close();
            }
        }
        
    }
}

补充知识

CuratorFramework提供的方法：

create()	开始创建操作， 可以调用额外的方法(比如方式mode 或者后台执行background) 并在最后调用forPath()指定要操作的ZNode
delete()	开始删除操作. 可以调用额外的方法(版本或者后台处理version or background)并在最后调用forPath()指定要操作的ZNode
checkExists()	开始检查ZNode是否存在的操作. 可以调用额外的方法(监控或者后台处理)并在最后调用forPath()指定要操作的ZNode
getData()	开始获得ZNode节点数据的操作. 可以调用额外的方法(监控、后台处理或者获取状态watch, background or get stat) 并在最后调用forPath()指定要操作的ZNode
setData()	开始设置ZNode节点数据的操作. 可以调用额外的方法(版本或者后台处理) 并在最后调用forPath()指定要操作的ZNode
getChildren()	开始获得ZNode的子节点列表。 以调用额外的方法(监控、后台处理或者获取状态watch, background or get stat) 并在最后调用forPath()指定要操作的ZNode
inTransaction()	开始是原子ZooKeeper事务. 可以复合create, setData, check, and/or delete 等操作然后调用commit()作为一个原子操作提交

事件类型以及事件的方法如下：

Event Type	Event Methods
CREATE	getResultCode() and getPath()
DELETE	getResultCode() and getPath()
EXISTS	getResultCode(), getPath() and getStat()
GETDATA	getResultCode(), getPath(), getStat() and getData()
SETDATA	getResultCode(), getPath() and getStat()
CHILDREN	getResultCode(), getPath(), getStat(), getChildren()
WATCHED	getWatchedEvent()