本文来自:http://www.cnblogs.com/yukaizhao/archive/2008/11/10/memcached_client_usage.html
一. 背景:
在大访问量的web程序开发中,数据库常常会称为性能的瓶颈。为了缓解数据库的压力,我们频繁的使用缓存,而asp.net自带的Cache很强大,但是有先天的不足,它是进程内的缓存,当站点由多台服务器负载均衡时,当缓存在有数据更新时,我们不能同时将更新后的数据同步到两台或多台web server上。所幸的是老外的大牛开发了memcached分布式缓存,它的性能非凡,memcached常用的.net的client类库有两个分别是:http://code.google.com/p/beitmemcached/,http://sourceforge.net/projects/memcacheddotnet/,我个人推荐使用后一个。
有关memcached的介绍和在控制台中的简单调用请参考:分布式缓存系统Memcached简介与实践
二. 如何使用
- 安装memcached server端,下载dot net版本的客户端,请参考分布式缓存系统Memcached简介与实践
- 在asp.net项目中使用memcached客户端访问服务端
思路:
1) 我们在站点启动时即启动memcached的client端,在站点停止时停掉client端,释放占用的端口资源;
这一点只要把启动和关闭放到Global的Application_Start和Application_End中执行,即可。由于整个网站的运行期间,我们都希望不需要再重新生成MemcachedClient类的实例,所以我们在Global中声明了一个静态的实例来存放此Client。并用一个public的属性RemoteCache和IsRemoteCacheAvailable来暴露MemcachedClient的引用和其是否可用。
2) 为了方便使用我们需要建一个System.Web.UI.Page类的基类PageBase,在此基类中引用Memcached client的客户端访问类实例,然后新建的所有aspx页面的基类继承PageBase就可以了。
这儿也很容已做到,我们只需找到 Global appInstance = HttpContext.Current.ApplicationInstance as Global;然后引用Global中暴露的两个属性即可。需要注意的是在程序中引用Global是通过HttpContext.Current.ApplicationInstance而不是HttpContext.Current.Applicatioin,后者只是一个键值对的集合,而前者是网站的HttpApplication的实例
请参考Global和PageBase的代码:
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using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Web.Caching;
using Memcached.ClientLibrary;
using System.Collections.Generic;
using log4net;
using Forum.Models;
using Forum.UI.Proxy;
namespace Forum.UI
{
public class PageBase : Page
{
#region RemoteCache & IsRemoteCacheAvailable
protected MemcachedClient RemoteCache
{
get
{
if (HttpContext.Current.ApplicationInstance == null) return null;
Global appInstance = HttpContext.Current.ApplicationInstance as Global;
if (appInstance == null) return null;
return appInstance.RemoteCache;
}
}
protected bool IsRemoteCacheAvailable
{
get
{
return RemoteCache != null;
}
}
#endregion
}
}
三. 后记
仅仅是个人使用心得,如果有问题,请回复讨论。
我的微博地址是:http://weibo.com/yukaizhao 我会把一些技术心得碎片写到微博中,欢迎关注。