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asp.net高性能之路：无缝切换HttpRuntime.Cache与Memcached，附代码

原作者: [db:作者] 来自: [db:来源] 收藏邀请

之前网站一直使用asp.net自带的cache，也就是HttpRuntime.Cache。这个的优点是进程内cache，效率非常高，同时对于缓存的对象可以直接获得

引用，并进行修改，不需要再进行清空缓存。但是使用HttpRuntime.Cache，无法进行扩展，也无法使用web园等等。

方案

之前有看dudu写的关于northscale memcached的文章，觉得很不错，故进行了一下尝试。由于初次使用，出问题的时候要能随时切换回HttpRuntime.Cache，

故使用了策略模式，实现无缝切换缓存模式的功能。Memcached的封装类请在https://github.com/enyim/EnyimMemcached/downloads进行下载，我使用的是Northscale.Store.2.8

接口

View Code

using System;
using System.Collections.Generic;
using System.Web;


/// <summary>
/// 缓存策略接口
/// </summary>
public interface ICacheStrategy
{
void AddObject(string objId, object o);

void AddObjectWithTimeout(string objId, object o, int timeoutSec);

void AddObjectWithFileChange(string objId, object o, string file);

//void AddObjectWithDepend(string objId, object o, string[] dependKey);

void RemoveObject(string objId);

object RetrieveObject(string objId);

int TimeOut { set; get; }
}

HttpRuntime.Cache实现类

View Code

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Caching;

/// <summary>
/// 默认的缓存策略，实现了缓存策略接口
/// </summary>
public class DefaultCacheStrategy : ICacheStrategy
{
private static readonly DefaultCacheStrategy instance = new DefaultCacheStrategy();

protected static volatile System.Web.Caching.Cache webCache = System.Web.HttpRuntime.Cache;

protected int _timeOut = 1; //默认缓存一分钟，也可以单独设置对象的超时时间


/// <summary>
/// Initializes the <see cref="DefaultCacheStrategy"/> class.
/// </summary>
    static DefaultCacheStrategy()
    {
//lock (syncObj)
//{
// //System.Web.HttpContext context = System.Web.HttpContext.Current;
// //if(context != null)
// // webCache = context.Cache;
// //else
// webCache = System.Web.HttpRuntime.Cache;
//} 
    }


public int TimeOut
    {
set { _timeOut = value > 0 ? value : 6000; }
get { return _timeOut > 0 ? _timeOut : 6000; }
    }


public static System.Web.Caching.Cache GetWebCacheObj
    {
get { return webCache; }
    }

public void AddObject(string objId, object o)
    {

if (objId == null || objId.Length == 0 || o == null)
        {
return;
        }

        CacheItemRemovedCallback callBack = new CacheItemRemovedCallback(onRemove);

if (TimeOut == 6000)
        {
            webCache.Insert(objId, o, null, DateTime.MaxValue, TimeSpan.Zero, System.Web.Caching.CacheItemPriority.High, callBack);
        }
else
        {
            webCache.Insert(objId, o, null, DateTime.Now.AddMinutes(TimeOut), System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.High, callBack);
        }
    }


public void AddObjectWithTimeout(string objId, object o, int timeoutSec)
    {
if (objId == null || objId.Length == 0 || o == null || timeoutSec <= 0)
        {
return;
        }

        CacheItemRemovedCallback callBack = new CacheItemRemovedCallback(onRemove);

        webCache.Insert(objId, o, null, System.DateTime.Now.AddSeconds(timeoutSec), System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.High, callBack);
    }

public void AddObjectWithFileChange(string objId, object o, string file)
    {
if (objId == null || objId.Length == 0 || o == null)
        {
return;
        }

        CacheItemRemovedCallback callBack = new CacheItemRemovedCallback(onRemove);

        CacheDependency dep = new CacheDependency(file);

        webCache.Insert(objId, o, dep, Cache.NoAbsoluteExpiration, TimeSpan.FromHours(1), System.Web.Caching.CacheItemPriority.High, callBack);
    }


//public void AddObjectWithDepend(string objId, object o, string[] dependKey)
//{
//    if (objId == null || objId.Length == 0 || o == null)
//    {
//        return;
//    }

//    CacheItemRemovedCallback callBack = new CacheItemRemovedCallback(onRemove);

//    CacheDependency dep = new CacheDependency(null, dependKey, DateTime.Now);

//    webCache.Insert(objId, o, dep, System.DateTime.Now.AddMinutes(TimeOut), System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.High, callBack);
//}

public void onRemove(string key, object val, CacheItemRemovedReason reason)
    {
switch (reason)
        {
case CacheItemRemovedReason.DependencyChanged:
break;
case CacheItemRemovedReason.Expired:
                {
//CacheItemRemovedCallback callBack = new CacheItemRemovedCallback(this.onRemove);

//webCache.Insert(key, val, null, System.DateTime.Now.AddMinutes(TimeOut),
// System.Web.Caching.Cache.NoSlidingExpiration,
// System.Web.Caching.CacheItemPriority.High,
// callBack);
                    break;
                }
case CacheItemRemovedReason.Removed:
                {
break;
                }
case CacheItemRemovedReason.Underused:
                {
break;
                }
default: break;
        }

//TODO: write log here
    }


public void RemoveObject(string objId)
    {
//objectTable.Remove(objId);
        if (objId == null || objId.Length == 0)
        {
return;
        }
        webCache.Remove(objId);
    }


public object RetrieveObject(string objId)
    {
//return objectTable[objId];

if (objId == null || objId.Length == 0)
        {
return null;
        }

return webCache.Get(objId);
    }
}

Memcached 实现类

View Code

using System;
using System.Collections.Generic;
using System.Web;
using NorthScale.Store;
using Enyim.Caching.Memcached;

/// <summary>
/// Summary description for EnyimMemcachedProvider
/// </summary>
public class EnyimMemcachedProvider
{

private static NorthScaleClient client;

static EnyimMemcachedProvider()
        {
try
            {
                client = new NorthScaleClient();
            }
catch (Exception ex)
            {
                log4net.LogManager.GetLogger("SojumpLog").Info("EnyimMemcachedProvider", ex);
            }
        }

#region ICacheProvider Members

public void Add(string key, object value)
        {
if (client != null)
            {
                client.Store(StoreMode.Set, key, value);
            }
        }

public void Add(string key, object value, int cacheSecond)
        {
if (client != null)
            {
                client.Store(StoreMode.Set, key, value, new TimeSpan(0, 0, cacheSecond));
            }
        }

public object GetData(string key)
        {
if (client == null)
            {
return null;
            }
return client.Get(key);
        }

public void Remove(string key)
        {
if (client != null)
            {
                client.Remove(key);
            }
        }

#endregion

}

策略类

View Code

using System;
using System.Collections.Generic;
using System.Web;
using System.Configuration;

/// <summary>
/// The caching manager
/// </summary>
public class CachingManager
{
private static ICacheStrategy cs;
private static volatile CachingManager instance = null;
private static object lockHelper = new object();

//private static System.Timers.Timer cacheConfigTimer = new System.Timers.Timer(15000);//Interval in ms


static CachingManager()
    {
string type = ConfigurationManager.AppSettings["CacheStrategy"];
if (type == "2")
            cs = new MemCacheStrategy();
else
            cs = new DefaultCacheStrategy();

////Set timer
        //cacheConfigTimer.AutoReset = true;
//cacheConfigTimer.Enabled = true;
//cacheConfigTimer.Elapsed += new System.Timers.ElapsedEventHandler(Timer_Elapsed);
//cacheConfigTimer.Start();
    }


private static void Timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
//TODO:
    }


public static CachingManager GetCachingService()
    {
if (instance == null)
        {
lock (lockHelper)
            {
if (instance == null)
                {
                    instance = new CachingManager();
                }
            }
        }

return instance;
    }


public virtual void AddObject(string key, object o)
    {
if (String.IsNullOrEmpty(key) || o == null) return;

lock (lockHelper)
        {
if (cs.TimeOut <= 0) return;

            cs.AddObject(key, o);
        }
    }


public virtual void AddObject(string key, object o, int timeout)
    {
if (String.IsNullOrEmpty(key) || o == null) return;

lock (lockHelper)
        {
if (cs.TimeOut <= 0) return;

            cs.AddObjectWithTimeout(key, o, timeout);
        }
    }

public virtual void AddObject(string key, object o, string file)
    {
if (String.IsNullOrEmpty(key) || o == null) return;

lock (lockHelper)
        {
if (cs.TimeOut <= 0) return;

            cs.AddObjectWithFileChange(key, o, file);
        }
    }

public virtual object RetrieveObject(string objectId)
    {
return cs.RetrieveObject(objectId);
    }


public virtual void RemoveObject(string key)
    {
lock (lockHelper)
        {
            cs.RemoveObject(key);
        }
    }


public void LoadCacheStrategy(ICacheStrategy ics)
    {
lock (lockHelper)
        {
            cs = ics;
        }
    }


//public void LoadDefaultCacheStrategy()
//{
//    lock (lockHelper)
//    {
//        cs = new DefaultCacheStrategy();
//    }
//}
}

调用代码

string key ="test"

CachingManager cm = new CachingManager();

cm.AddObject(key,new Object(),60);//缓存对象60秒。

不足

Memcached无法使用CacheDependency，需要自己去进行处理。如你的缓存对象依赖于文件，则在文件修改时要直接清空缓存。

Memcached也无法清空某一类的缓存对象，有时因为数据库做了修改，你要清空key以activity_开头的一系列对象的话，是做不到的。

变通的方案是先将key加入到List或Dictionary中，如下代码：

View Code

public void ClearCacheByPattern(string pattern)
 {

if(client!=null)
return;

object c = client.Get("globel_cacheitems");

if (c==null)
return;

         List<string> cacheitems = (List<string>) c;

foreach (string cacheitem in cacheitems)

             {

if (cacheitem.StartsWith(pattern))

                 {

                     client.Remove(cacheitem);

                 }

             }
  }