memcached下集合对象的缓存-优快云博客

本文链接：https://blog.youkuaiyun.com/wangsilence/article/details/84620123

本文介绍了一种使用Memcached缓存粒度更细的有效方法，通过将传统的key-value(list)结构转变为key_index-list[index]的方式，解决了修改list内单一元素的问题，并提供了一种利用计数器维护index的方法。

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memcached作为当下比较流行的缓存利器，有很多很多优点，也有一些自身的缺点。
很多时候，需要缓存一个list，可是Memcached颗粒度并不支持修改其中的元素，所以只能采用replace，就是把list整个取出，然后add/remove/modify之类再set回去。
这种解决方案不是很好，比如list增长的很大，又比如list内的对象都比较大。
很多时候可能存在这样的需求，list内的对象都有一定时效，比如30分钟，如果整个list存入memcached显然很难做到这一点，随着set整个List操作，list的时效会恢复成30分钟，虽然可能list内的部分元素你已经不再需要了，可是怎么把它们remove是个问题，这个问题可以在把整个List取出来进行一堆复杂算法之后可以实现，不过这种方法显然很糟糕。
这里提供了一种方法，可以尝试一下。
原本的数据结构式key-value(list);
现修改为 key_index - list[index]。
很显然这样设计的话，需要维护这个index。可能你觉得可以用List下标来实现。可是随着里面元素的增加修改删除或者失效，这样并不起作用，而且运用于分布式系统下这种方法并不明智。
这样的话我们需要一个东西来存储index。 memcached自身提供了一个counter功能。我们可以利用起来。
另外如果批量存进去之后，如何批量取出又是个问题了。还好memcached为我们提供了get(Collection)方法。


import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeoutException;

import net.rubyeye.xmemcached.Counter;
import net.rubyeye.xmemcached.GetsResponse;
import net.rubyeye.xmemcached.MemcachedClient;
import net.rubyeye.xmemcached.exception.MemcachedException;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MemcachedClientManager{

	private static final MemcachedClientManager instance = new MemcachedClientManager();

	private static final int storeTime = 5 * 60;

	//待更新列表保存时效
	private static final String updateObjKey = "UpdateObj_";

	private static MemcachedClient memcachedClient;
	private static final long counterInitValue = 1;
	private static final long maxavilableValue = 10000;

	private static final String UpdateObjCounter = "UpdateObjCounter";

	public static List<String> UpdateObjList = new ArrayList<String>((int)maxavilableValue);

	static{
		for( long i = counterInitValue ; i <= maxavilableValue ; i++ ){
			UpdateObjList.add(new StringBuffer(updateObjKey).append(i).toString());
		}
	}

	private MemcachedClientManager()
	{
		ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
		memcachedClient = (MemcachedClient) app.getBean("memcachedClient");
	}

	public static MemcachedClientManager getInstance()
	{
		return instance;
	}

	/**
	 * 封装delete方法
	 */
	public void delete(String arg0) {

		try {
			memcachedClient.deleteWithNoReply(arg0);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (MemcachedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	/**
	 * 封装gets方法
	 */
	public <T> T get(String arg0) {

		try {
			return memcachedClient.get(arg0);
		} catch (TimeoutException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (MemcachedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}

	public void replace(String arg0, int arg1, Object arg2) {
		try {
			memcachedClient.replaceWithNoReply(arg0, arg1, arg2);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (MemcachedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	public void set(String arg0, int arg1, Object arg2) {
		try {
			memcachedClient.setWithNoReply(arg0, arg1, arg2);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (MemcachedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	public <T> Map<String, GetsResponse<T>> gets(Collection<String> arg0) {
		// TODO Auto-generated method stub
		try {
			return memcachedClient.gets(arg0);
		} catch (TimeoutException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (MemcachedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}

	/**
	 * 计数器取值，支持分布式系统
	 */
	private long getCount(long min,long max,String key) {
		long count = min;
		Counter counter = memcachedClient.getCounter(key);
		try {
			count = counter.incrementAndGet();
			if(count > max){
				counter.set(min);
				count = min;
			}
		} catch (MemcachedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (TimeoutException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return count;
	}

	/**
	 * 存入list_index-value
	 */
	public void storeUpdateList(Bean obj)
	{
		try {
			long count = getCount(counterInitValue,maxavilableValue,UpdateObjCounter);
			String key = new StringBuffer(updateObjKey).append(count).toString();
			memcachedClient.setWithNoReply(key, storeTime, obj);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (MemcachedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	/**
	 * 根据键集获取值集
	 */
	@SuppressWarnings("unchecked")
	public <T> List<T> getKeys(List<String> keylist){
		List<T> rt = new ArrayList<T>();
		Map<String, GetsResponse<Object>>  map = gets(keylist);
		if( null != map && map.size() > 0 )
		{
			List<GetsResponse<Object>> list = new ArrayList<GetsResponse<Object>>(map.values());
			for(GetsResponse<Object> temp : list){
				T t = (T) temp.getValue();
				rt.add(t);
			}
		}
		return rt;
	}
}

application.xml


<?xml version="1.0" encoding="UTF-8"?>
<beans
	xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd">
	<!-- http://code.google.com/p/xmemcached/wiki/Spring_Integration -->
	<context:property-placeholder location="memcache.properties" />
	<bean
		id="memcachedClientBuilder"
		class="net.rubyeye.xmemcached.XMemcachedClientBuilder"
		p:connectionPoolSize="${memcached.connectionPoolSize}"
		p:failureMode="${memcached.failureMode}"
		p:healSessionInterval="${memcached.healSessionInterval}">
		<!-- XMemcachedClientBuilder have two arguments.First is server list,and 
			second is weights array. -->
		<constructor-arg>
			<list>
				<bean class="java.net.InetSocketAddress">
					<constructor-arg>
						<value>${memcached.server1.host}</value>
					</constructor-arg>
					<constructor-arg>
						<value>${memcached.server1.port}</value>
					</constructor-arg>
				</bean>
				<!-- <bean class="java.net.InetSocketAddress">
					<constructor-arg>
						<value>${memcached.server2.host}</value>
					</constructor-arg>
					<constructor-arg>
						<value>${memcached.server2.port}</value>
					</constructor-arg>
				</bean> -->
			</list>
		</constructor-arg>
		<constructor-arg>
			<list>
				<value>${memcached.server1.weight}</value>
				<!-- <value>${memcached.server2.weight}</value> -->
			</list>
		</constructor-arg>
		<property name="commandFactory">
			<bean class="net.rubyeye.xmemcached.command.TextCommandFactory" />
		</property>
		<property name="sessionLocator">
			<bean class="net.rubyeye.xmemcached.impl.KetamaMemcachedSessionLocator" />
		</property>
		<property name="transcoder">
			<bean class="net.rubyeye.xmemcached.transcoders.SerializingTranscoder" />
		</property>
	</bean>
	<!-- Use factory bean to build memcached client -->
	<bean
		id="memcachedClient"
		factory-bean="memcachedClientBuilder"
		factory-method="build"
		destroy-method="shutdown" />
</beans>

memcache.properties


#连接池大小即客户端个数
memcached.connectionPoolSize=50
memcached.failureMode=true
memcached.healSessionInterval=60000
#server1
memcached.server1.host=127.0.0.1
memcached.server1.port=11211
memcached.server1.weight=6
#server2
#memcached.server2.host=127.0.0.1
#memcached.server2.port=11212
#memcached.server2.weight=4

附上测试代码


public static void main(String[] args) {
		long beginTime = System.currentTimeMillis();
		MemcachedClientManager manager = MemcachedClientManager.getInstance();
		for( int i = 0 ; i< 12000 ; i ++ ){
			Bean obj = new Bean();
			obj.setName(String.valueOf(i));
			manager.storeUpdateList(obj);
		}

		List<Bean> rtList = manager.getKeys(MemcachedClientManager.UpdateObjList);

		long endTime = System.currentTimeMillis();

		//因为keylist设置了10000个 counter最大值也是10000 所以取出的列表最大为10000个
		System.out.println(rtList.size());
		System.out.println(endTime - beginTime);
	}