Zookeeper分布式队列的实现

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Zookeeper分布式队列的实现

2024-09-19 01:38:05 218人阅读

摘要：本文要通过zookeeper实现一个简单可靠的分布式队列

本文源码请在这里下载：https://github.com/appleappleapple/DistributeLearning

一、队列

Zookeeper可以处理两种类型的队列：
（1）同步队列
当一个队列的成员都聚齐时，这个队列才可用，否则一直等待所有成员到达。例如一个班去旅游，看是否所有人都到齐了，到齐了就发车。例如有个大任务分解为多个子任务，要所有子任务都完成了才能进入到下一流程。
（2）先进先出队列
按照FIFO方式进行入队和出队

例如实现生产者和消费者模型

二、实现思路
（1）同步队列
在zookeeper中先创建一个根目录 queue_sync，做为队列队列的消费者监视/queue/start节点，刚开始还没有这个节点，所以什么都不会做。入队操作就是在queue_sync下创建子节点，然后计算子节点的总数，看是否和队列的目标数量相同。如果相同，创建/queue_sync/start节点，由于/queue_sync/start这个节点有了状态变化，zookeeper就会通知监视者：队员已经到齐了，监视者得到通知后进行自己的后续流程

实现代码

package com.github.distribute.queue;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.I0Itec.zkclient.ExceptionUtil;
import org.I0Itec.zkclient.exception.ZkNoNodeException;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 分布式队列，同步队列的实现
 * 
 * @author linbingwen
 *
 * @param <T>
 */
public class DistributedQueue<T> {
	private static Logger logger = LoggerFactory.getLogger(DistributedQueue.class);

	protected final ZooKeeper zooKeeper;// 用于操作zookeeper集群
	protected final String root;// 代表根节点
	private int queueSize;
	private String startPath = "/queue/start";

	protected static final String Node_NAME = "n_";// 顺序节点的名称

	public DistributedQueue(ZooKeeper zooKeeper, String root, int queueSize) {
		this.zooKeeper = zooKeeper;
		this.root = root;
		this.queueSize = queueSize;
		init();
	}

	/**
	 * 初始化根目录
	 */
	private void init() {
		try {
			Stat stat = zooKeeper.exists(root, false);// 判断一下根目录是否存在
			if (stat == null) {
				zooKeeper.create(root, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
			}
			zooKeeper.delete(startPath, -1); // 删除队列满的标志
		} catch (Exception e) {
			logger.error("create rootPath error", e);
		}
	}

	/**
	 * 获取队列的大小
	 * 
	 * @return
	 * @throws Exception
	 */
	public int size() throws Exception {
		return zooKeeper.getChildren(root, false).size();
	}

	/**
	 * 判断队列是否为空
	 * 
	 * @return
	 * @throws Exception
	 */
	public boolean isEmpty() throws Exception {
		return zooKeeper.getChildren(root, false).size() == 0;
	}

	/**
	 * bytes 转object
	 * 
	 * @param bytes
	 * @return
	 */
	private Object ByteToObject(byte[] bytes) {
		Object obj = null;
		try {
			// bytearray to object
			ByteArrayInputStream bi = new ByteArrayInputStream(bytes);
			ObjectInputStream oi = new ObjectInputStream(bi);

			obj = oi.readObject();
			bi.close();
			oi.close();
		} catch (Exception e) {
			logger.error("translation" + e.getMessage());
			e.printStackTrace();
		}
		return obj;
	}

	/**
	 * Object 转byte
	 * 
	 * @param obj
	 * @return
	 */
	private byte[] ObjectToByte(java.lang.Object obj) {
		byte[] bytes = null;
		try {
			// object to bytearray
			ByteArrayOutputStream bo = new ByteArrayOutputStream();
			ObjectOutputStream oo = new ObjectOutputStream(bo);
			oo.writeObject(obj);

			bytes = bo.toByteArray();

			bo.close();
			oo.close();
		} catch (Exception e) {
			logger.error("translation" + e.getMessage());
			e.printStackTrace();
		}
		return bytes;
	}

	/**
	 * 向队列提供数据,队列满的话会阻塞等待直到start标志位清除
	 * 
	 * @param element
	 * @return
	 * @throws Exception
	 */
	public boolean offer(T element) throws Exception {
		// 构建数据节点的完整路径
		String nodeFullPath = root.concat("/").concat(Node_NAME);
		try {
			if (queueSize > size()) {
				// 创建持久的节点，写入数据
				zooKeeper.create(nodeFullPath, ObjectToByte(element), ZooDefs.Ids.OPEN_ACL_UNSAFE,
						CreateMode.PERSISTENT);
				// 再判断一下队列是否满
				if (queueSize > size()) {
					zooKeeper.delete(startPath, -1); // 确保不存在
				} else {
					zooKeeper.create(startPath, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
				}
			} else {
				// 创建队列满的标记
				if (zooKeeper.exists(startPath, false) != null) {
					zooKeeper.create(startPath, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
				}

				final CountDownLatch latch = new CountDownLatch(1);
				final Watcher previousListener = new Watcher() {
					public void process(WatchedEvent event) {
						if (event.getType() == EventType.NodeDeleted) {
							latch.countDown();
						}
					}
				};

				// 如果节点不存在会出现异常
				zooKeeper.exists(startPath, previousListener);
				latch.await();
				offer(element);

			}
		} catch (ZkNoNodeException e) {
			logger.error("", e);
		} catch (Exception e) {
			throw ExceptionUtil.convertToRuntimeException(e);
		}
		return true;
	}

	/**
	 * 从队列取数据,当有start标志位时，开始取数据，全部取完数据后才删除start标志
	 * 
	 * @return
	 * @throws Exception
	 */
	@SuppressWarnings("unchecked")
	public T poll() throws Exception {

		try {
			// 队列还没满
			if (zooKeeper.exists(startPath, false) == null) {
				final CountDownLatch latch = new CountDownLatch(1);
				final Watcher previousListener = new Watcher() {
					public void process(WatchedEvent event) {
						if (event.getType() == EventType.NodeCreated) {
							latch.countDown();
						}
					}
				};

				// 如果节点不存在会出现异常
				zooKeeper.exists(startPath, previousListener);

				// 如果节点不存在会出现异常
				latch.await();
			}

			List<String> list = zooKeeper.getChildren(root, false);
			if (list.size() == 0) {
				return null;
			}
			// 将队列按照由小到大的顺序排序
			Collections.sort(list, new Comparator<String>() {
				public int compare(String lhs, String rhs) {
					return getNodeNumber(lhs, Node_NAME).compareTo(getNodeNumber(rhs, Node_NAME));
				}
			});

			/**
			 * 将队列中的元素做循环，然后构建完整的路径，在通过这个路径去读取数据
			 */
			for (String nodeName : list) {
				String nodeFullPath = root.concat("/").concat(nodeName);
				try {
					T node = (T) ByteToObject(zooKeeper.getData(nodeFullPath, false, null));
					zooKeeper.delete(nodeFullPath, -1);
					return node;
				} catch (ZkNoNodeException e) {
					logger.error("", e);
				}
			}
			return null;
		} catch (Exception e) {
			throw ExceptionUtil.convertToRuntimeException(e);
		}

	}

	/**
	 * 截取节点的数字的方法
	 * 
	 * @param str
	 * @param nodeName
	 * @return
	 */
	private String getNodeNumber(String str, String nodeName) {
		int index = str.lastIndexOf(nodeName);
		if (index >= 0) {
			index += Node_NAME.length();
			return index <= str.length() ? str.substring(index) : "";
		}
		return str;

	}

}

代码还没验证，可能会有问题！

（2）先进先出队列

在zookeeper中先创建一个根目录 queue_fifo，做为队列。入队操作就是在queue_fifo下创建自增序的子节点，并把数据放入节点内。出队操作就是先找到queue_fifo下序号最下的那个节点，取出数据，然后删除此节点。

实现代码：

package com.github.distribute.queue;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import org.I0Itec.zkclient.ExceptionUtil;
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.exception.ZkNoNodeException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.github.distribute.lock.zookeeper.BaseDistributedLock;

/**
 * 分布式队列，生产者，消费者的实现
 * @author linbingwen
 *
 * @param <T>
 */
public class DistributedSimpleQueue<T> {

	private static Logger logger = LoggerFactory.getLogger(BaseDistributedLock.class);

	protected final ZkClient zkClient;//用于操作zookeeper集群
	protected final String root;//代表根节点

	protected static final String Node_NAME = "n_";//顺序节点的名称
	


	public DistributedSimpleQueue(ZkClient zkClient, String root) {
		this.zkClient = zkClient;
		this.root = root;
	}
    
	//获取队列的大小
	public int size() {
		/**
		 * 通过获取根节点下的子节点列表
		 */
		return zkClient.getChildren(root).size();
	}
	
    //判断队列是否为空
	public boolean isEmpty() {
		return zkClient.getChildren(root).size() == 0;
	}
	
	/**
	 * 向队列提供数据
	 * @param element
	 * @return
	 * @throws Exception
	 */
    public boolean offer(T element) throws Exception{
    	
    	//构建数据节点的完整路径
    	String nodeFullPath = root .concat( "/" ).concat( Node_NAME );
        try {
        	//创建持久的节点，写入数据
            zkClient.createPersistentSequential(nodeFullPath , element);
        }catch (ZkNoNodeException e) {
        	zkClient.createPersistent(root);
        	offer(element);
        } catch (Exception e) {
            throw ExceptionUtil.convertToRuntimeException(e);
        }
        return true;
    }


    //从队列取数据
	@SuppressWarnings("unchecked")
	public T poll() throws Exception {
		
		try {

			List<String> list = zkClient.getChildren(root);
			if (list.size() == 0) {
				return null;
			}
			//将队列按照由小到大的顺序排序
			Collections.sort(list, new Comparator<String>() {
				public int compare(String lhs, String rhs) {
					return getNodeNumber(lhs, Node_NAME).compareTo(getNodeNumber(rhs, Node_NAME));
				}
			});
			
			/**
			 * 将队列中的元素做循环，然后构建完整的路径，在通过这个路径去读取数据
			 */
			for ( String nodeName : list ){
				
				String nodeFullPath = root.concat("/").concat(nodeName);	
				try {
					T node = (T) zkClient.readData(nodeFullPath);
					zkClient.delete(nodeFullPath);
					return node;
				} catch (ZkNoNodeException e) {
					logger.error("",e);
				}
			}
			
			return null;
			
		} catch (Exception e) {
			throw ExceptionUtil.convertToRuntimeException(e);
		}

	}

	
	private String getNodeNumber(String str, String nodeName) {
		int index = str.lastIndexOf(nodeName);
		if (index >= 0) {
			index += Node_NAME.length();
			return index <= str.length() ? str.substring(index) : "";
		}
		return str;

	}

}

测试一下：

package com.github.distribute.queue;

import java.io.Serializable;

import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;

public class DistributedQueueTest {

	public static void main(String[] args) {
		ZkClient zkClient = new ZkClient("127.0.0.1:2181", 5000, 5000, new SerializableSerializer());
		DistributedSimpleQueue<SendObject> queue = new DistributedSimpleQueue<SendObject>(zkClient, "/Queue");
		new Thread(new ConsumerThread(queue)).start();
		new Thread(new ProducerThread(queue)).start();

	}

}

class ConsumerThread implements Runnable {
	private DistributedSimpleQueue<SendObject> queue;

	public ConsumerThread(DistributedSimpleQueue<SendObject> queue) {
		this.queue = queue;
	}

	public void run() {
		for (int i = 0; i < 10000; i++) {
			try {
				Thread.sleep((int) (Math.random() * 5000));// 随机睡眠一下
				SendObject sendObject = (SendObject) queue.poll();
				System.out.println("消费一条消息成功：" + sendObject);
			} catch (Exception e) {
			}
		}
	}
}

class ProducerThread implements Runnable {

	private DistributedSimpleQueue<SendObject> queue;

	public ProducerThread(DistributedSimpleQueue<SendObject> queue) {
		this.queue = queue;
	}

	public void run() {
		for (int i = 0; i < 10000; i++) {
			try {
				Thread.sleep((int) (Math.random() * 5000));// 随机睡眠一下
				SendObject sendObject = new SendObject(String.valueOf(i), "content" + i);
				queue.offer(sendObject);
				System.out.println("发送一条消息成功：" + sendObject);
			} catch (Exception e) {
			}
		}
	}

}

class SendObject implements Serializable {

	private static final long serialVersionUID = 1L;

	public SendObject(String id, String content) {
		this.id = id;
		this.content = content;
	}

	private String id;

	private String content;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getContent() {
		return content;
	}

	public void setContent(String content) {
		this.content = content;
	}

	@Override
	public String toString() {
		return "SendObject [id=" + id + ", content=" + content + "]";
	}

}

输出结果：

技术分享

本文源码请在这里下载：https://github.com/appleappleapple/DistributeLearning

Zookeeper分布式队列的实现

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Zookeeper分布式队列的实现

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