用异步缓存确保高流量网页及时更新与低错误率

3/26/2009来源:ASP.NET技巧人气:6864

      我通常的WEB开发中,有时我们会碰以这种情况,一个页面有很多模块组成,而这些模块之间是不关链的,就像一个网站的首页,里面有很多块块,有些是读新闻的,有些是读产品信息,还有一些部分是读论坛,博客之类的地方.而这个页面的要求是很高的,无论在什么情况下都要保证页面是可以正确打开的(当然服务器故障是没有办法的).而且网站的流量很大.

     通常这样的页面是需要生成静态页来保证页面正确的,但是这种做法会有很大的问题,如果网站中一个小块异常了,会导致整个页面不更新.

     现在我们给出这样一个解决方案:页面分两级缓存,一级为内存缓存,二级为文件缓存.这里的文件缓存是起辅助做用的,有一种特殊的情况,一个asp.net应用程序池是会重新初始化的,初始化完过后,内存数据会被清空,这个时候如果我们直接去执行数据访问程序,那么我们不能保证当时情况下程序的正确性和性能(对于程序调用过多的页面来说,执行速度慢,大量的并发请求会导致服务器崩溃).

       也就是说,对于页面程序来说,如果程序一执行会先去读内存,如果发现内存为空,那么改去读相应的缓存文件,如果文件还没生成,那么再执行程序(这种情况只在程序在服务器上第一运行是发生).

      为了确保页面更新及时,这里需要异步缓存,也就是说为每一个模块起一个线程来维护,如果线程方法执行成功,那么更新内存中的内容.这里建议把文件更新另起一个线程式,因为文件更新可以时间间隔长一起,结约系统资源.例如,每个模块内存更新速度是20秒,那么文件的可以设为5分钟.

      下面给出一段代码,这个主要是用于缓存处理的.....

 
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using System;  
using System.Data;  
using System.Configuration;  
using System.Linq;  
using System.xml.Linq;  
using System.IO;  
using System.Collections.Generic;  
using System.Threading;  
using System.Diagnostics;  
 
/// <summary>  
/// 本类主要负责处理根把相关参数设置缓存结果  
/// </summary>  
public class CacheSvr  
{  
    public delegate string ProcessDataDelegate(params object[] args);  
    public static string cacheDir = "D:\tmpFile";  
    public static Dictionary<string, string> cacheTable = new Dictionary<string, string>();  
    public static ReaderWriterLockSlim lockx = new ReaderWriterLockSlim();  
    public static Dictionary<string, Thread> threadTable = new Dictionary<string, Thread>();  
 
    public CacheSvr()  
    {  
        //  
        // TODO: Add constructor logic here  
        //  
    } 
 
    #region 文件缓存逻辑  
    /// <summary>  
    /// 保存程序执行结果致文件  
    /// </summary>  
    /// <param name="thisDelegate">所要执行的方法</param>  
    /// <param name="fileName">文件名</param>  
    /// <param name="args">参数列表</param>  
    /// <returns></returns>  
    public static void saveDataFile(CacheItem item)  
    {  
        string result = item.doProcess();  
        if (result.Length > 0)  
        {  
            write(result, item.CacheName);  
        }  
    }  
 
    /// <summary>  
    /// 写文件代码  
    /// </summary>  
    /// <param name="text">写入内容</param>  
    /// <param name="fileName">文件名</param>  
    public static void write(String text, string fileName)  
    {  
        try 
        {  
            String path = cacheDir;  
            path = path + fileName + ".cache";  
            Stream fsc = File.Create(path);  
            fsc.Close();  
            Stream fs = File.Open(path, FileMode.Open, Fileaccess.Write);  
            TextWriter tw = new StreamWriter(fs, System.Text.Encoding.GetEncoding(936));  
            tw.Write(text);  
            tw.Close();  
            fs.Close();  
        }  
        catch 
        {  
 
        }  
    }  
 
    public static string readFile(string fileName)  
    {  
        string content = "";  
        try 
        {  
            //Stopwatch watch = new Stopwatch();  
            //watch.Start();  
            String path = cacheDir;  
            path = path + fileName + ".cache";  
            Stream fs = File.Open(path, FileMode.Open, FileAccess.Read, FileShare.Read);  
            StreamReader tr = new StreamReader(fs, System.Text.Encoding.GetEncoding(936));  
            content = tr.ReadToEnd();  
            //content += "\r\n <!--read from file " + path + "--> \r\n";  
            tr.Close();  
            fs.Close();  
            //watch.Stop();  
            //content = content + "<!--执行时间为:" + watch.ElapsedMilliseconds + "-->\r\n";  
        }  
        catch 
        {  
            content = "";  
        }  
        return content;  
    } 
    #endregion 
 
    #region 内存缓存模块  
    /// <summary>  
    /// 内存缓存  
    /// </summary>  
    /// <param name="thisDelegate">所需执行的方法</param>  
    /// <param name="cacheName">内存中的名字</param>  
    /// <param name="args">参数列表</param>  
    /// <returns></returns>  
    public static void saveDataCache(CacheItem item)  
    {  
        string result = item.doProcess();  
        if (result.Length > 0)  
        {  
            cache(result, item.CacheName);  
        }  
    }  
 
    /// <summary>  
    /// 向内存中写入内容  
    /// </summary>  
    /// <param name="text"></param>  
    /// <param name="cacheName"></param>  
    public static void cache(string text, string cacheName)  
    {  
        lockx.EnterWriteLock();  
        try 
        {  
            //text += "\r\n<!--缓存更新,时间为:" + DateTime.Now.ToString() + "-->\r\n";  
            cacheTable[cacheName] = text;  
        }  
        catch { }  
        finally { lockx.ExitWriteLock(); }  
    }  
 
    public static void writelog(String text, string fileName)  
    {  
        try 
        {  
            String path = cacheDir;  
            path = path + fileName + ".cache";  
            if (!File.Exists(path))  
            {  
                Stream fsc = File.Create(path);  
                fsc.Close();  
            }  
            Stream fs = File.Open(path, FileMode.Append, FileAccess.Write);  
            TextWriter tw = new StreamWriter(fs, System.Text.Encoding.GetEncoding(936));  
            tw.Write(text);  
            tw.Close();  
            fs.Close();  
        }  
        catch 
        {  
 
        }  
    }  
 
    public static string readCache(string cacheName)  
    {  
        string content = "";  
        lockx.EnterReadLock();  
        try 
        {  
            bool result = cacheTable.TryGetValue(cacheName, out content);  
            //if (result)  
            //{  
            //    content += "\r\n <!--read from memory--> \r\n";  
            //}  
            return content;  
        }  
        catch 
        {  
            return "";  
        }  
        finally 
        {  
            lockx.ExitReadLock();  
        }  
    } 
    #endregion 
 
    #region 线程处理模块  
 
    public static void UpdateCache(object obj)  
    {  
        CacheItem thisCache = (CacheItem)obj;  
        writelog("线程:" + thisCache.CacheName + "--启动于:" + DateTime.Now.ToString() + "\r\n", "exceptions");  
        while (true)  
        {  
            try 
            {  
                saveDataCache(thisCache);  
            }  
            catch 
            {  
 
            }  
            Thread.Sleep(thisCache.memoryTime * 1000);//内存20秒更新  
        }  
    }  
 
    public static void UpdateFile(object obj)  
    {  
        CacheItem thisCache = (CacheItem)obj;  
        while (true)  
        {  
            try 
            {  
                saveDataFile(thisCache);  
            }  
            catch 
            {  
 
            }  
            Thread.Sleep(thisCache.fileTime * 1000);//文件2分钟缓存  
        }  
    }  
 
    public static Thread getThread(string threadName)  
    {  
        Thread tmpThread = null;  
        lockx.EnterReadLock();  
        try 
        {  
            if (threadTable.Keys.Contains(threadName))  
            {  
                tmpThread = threadTable[threadName];  
            }  
        }  
        catch 
        {  
        }  
        finally 
        {  
            lockx.ExitReadLock();  
        }  
        return tmpThread;  
    }  
 
    /// <summary>  
    /// 添加缓存  
    /// </summary>  
    /// <param name="item">缓存对象</param>  
    public static void saveCache(CacheItem item)  
    {  
        string mCacheName = item.CacheName + "_memory";  
        string fCacheName = item.CacheName + "_file";  
        Thread memoryCache = getThread(mCacheName);  
        Thread fileCache = getThread(fCacheName);  
        if (memoryCache == null)  
        {  
            memoryCache = new Thread(new ParameterizedThreadStart(UpdateCache));  
            memoryCache.IsBackground = true;  
            memoryCache.Start(item);  
        }  
        if (fileCache == null)  
        {  
            fileCache = new Thread(new ParameterizedThreadStart(UpdateFile));  
            fileCache.IsBackground = true;  
            fileCache.Start(item);  
        }  
        lockx.EnterWriteLock();  
        try 
        {  
            threadTable[mCacheName] = memoryCache;  
            threadTable[fCacheName] = fileCache;  
        }  
        catch { }  
        finally { lockx.ExitWriteLock(); }  
    }  
 
    public static string readCacheContent(CacheItem item)  
    {  
        //Stopwatch watch = new Stopwatch();  
        //watch.Start();  
        string content = readCache(item.CacheName);  
        if (content==null || content.Length < 0)  
        {  
            content = readFile(item.CacheName);  
            saveCache(item);  
        }  
        //读取缓存失败  
        if (content != null && content.Length <= 0)  
        {  
            //throw (new Exception("读取内容失败:" + item.CacheName));  
            content = item.doProcess();  
            //saveCache(item);  
        }  
        return content;  
        //watch.Stop();  
        //content += ("\r\n<!--方法执行时间:" + watch.ElapsedMilliseconds + "-->\r\n");  
    } 
    #endregion 
 
    #region 公共处理  
    public static string saveCache(string cacheName, ProcessDataDelegate mainMathod, object[] args)  
    {  
        using (CacheItem tmpCache = new CacheItem())  
        {  
            tmpCache.CacheName = cacheName;  
            tmpCache.CacheDelegate = mainMathod;  
            tmpCache.CacheArgs = args;  
            string content = "";  
            content = readCacheContent(tmpCache);  
            return content;  
        }  
    } 
    #endregion  

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Xml.Linq;
using System.IO;
using System.Collections.Generic;
using System.Threading;
using System.Diagnostics;

/// <summary>
/// 本类主要负责处理根把相关参数设置缓存结果
/// </summary>
public class CacheSvr
{
    public delegate string ProcessDataDelegate(params object[] args);
    public static string cacheDir = "D:\tmpFile";
    public static Dictionary<string, string> cacheTable = new Dictionary<string, string>();
    public static ReaderWriterLockSlim lockx = new ReaderWriterLockSlim();
    public static Dictionary<string, Thread> threadTable = new Dictionary<string, Thread>();

    public CacheSvr()
    {
        //
        // TODO: Add constructor logic here
        //
    }

    #region 文件缓存逻辑
    /// <summary>
    /// 保存程序执行结果致文件
    /// </summary>
    /// <param name="thisDelegate">所要执行的方法</param>
    /// <param name="fileName">文件名</param>
    /// <param name="args">参数列表</param>
    /// <returns></returns>
    public static void saveDataFile(CacheItem item)
    {
        string result = item.doProcess();
        if (result.Length > 0)
        {
            write(result, item.CacheName);
        }
    }

    /// <summary>
    /// 写文件代码
    /// </summary>
    /// <param name="text">写入内容</param>
    /// <param name="fileName">文件名</param>
    public static void write(String text, string fileName)
    {
        try
        {
            String path = cacheDir;
            path = path + fileName + ".cache";
            Stream fsc = File.Create(path);
            fsc.Close();
            Stream fs = File.Open(path, FileMode.Open, FileAccess.Write);
            TextWriter tw = new StreamWriter(fs, System.Text.Encoding.GetEncoding(936));
            tw.Write(text);
            tw.Close();
            fs.Close();
        }
        catch
        {

        }
    }

    public static string readFile(string fileName)
    {
        string content = "";
        try
        {
            //Stopwatch watch = new Stopwatch();
            //watch.Start();
            String path = cacheDir;
            path = path + fileName + ".cache";
            Stream fs = File.Open(path, FileMode.Open, FileAccess.Read, FileShare.Read);
            StreamReader tr = new StreamReader(fs, System.Text.Encoding.GetEncoding(936));
            content = tr.ReadToEnd();
            //content += "\r\n <!--read from file " + path + "--> \r\n";
            tr.Close();
            fs.Close();
            //watch.Stop();
            //content = content + "<!--执行时间为:" + watch.ElapsedMilliseconds + "-->\r\n";
        }
        catch
        {
            content = "";
        }
        return content;
    }
    #endregion

    #region 内存缓存模块
    /// <summary>
    /// 内存缓存
    /// </summary>
    /// <param name="thisDelegate">所需执行的方法</param>
    /// <param name="cacheName">内存中的名字</param>
    /// <param name="args">参数列表</param>
    /// <returns></returns>
    public static void saveDataCache(CacheItem item)
    {
        string result = item.doProcess();
        if (result.Length > 0)
        {
            cache(result, item.CacheName);
        }
    }

    /// <summary>
    /// 向内存中写入内容
    /// </summary>
    /// <param name="text"></param>
    /// <param name="cacheName"></param>
    public static void cache(string text, string cacheName)
    {
        lockx.EnterWriteLock();
        try
        {
            //text += "\r\n<!--缓存更新,时间为:" + DateTime.Now.ToString() + "-->\r\n";
            cacheTable[cacheName] = text;
        }
        catch { }
        finally { lockx.ExitWriteLock(); }
    }

    public static void writelog(String text, string fileName)
    {
        try
        {
            String path = cacheDir;
            path = path + fileName + ".cache";
            if (!File.Exists(path))
            {
                Stream fsc = File.Create(path);
                fsc.Close();
            }
            Stream fs = File.Open(path, FileMode.Append, FileAccess.Write);
            TextWriter tw = new StreamWriter(fs, System.Text.Encoding.GetEncoding(936));
            tw.Write(text);
            tw.Close();
            fs.Close();
        }
        catch
        {

        }
    }

    public static string readCache(string cacheName)
    {
        string content = "";
        lockx.EnterReadLock();
        try
        {
            bool result = cacheTable.TryGetValue(cacheName, out content);
            //if (result)
            //{
            //    content += "\r\n <!--read from memory--> \r\n";
            //}
            return content;
        }
        catch
        {
            return "";
        }
        finally
        {
            lockx.ExitReadLock();
        }
    }
    #endregion

    #region 线程处理模块

    public static void UpdateCache(object obj)
    {
        CacheItem thisCache = (CacheItem)obj;
        writelog("线程:" + thisCache.CacheName + "--启动于:" + DateTime.Now.ToString() + "\r\n", "exceptions");
        while (true)
        {
            try
            {
                saveDataCache(thisCache);
            }
            catch
            {

            }
            Thread.Sleep(thisCache.memoryTime * 1000);//内存20秒更新
        }
    }

    public static void UpdateFile(object obj)
    {
        CacheItem thisCache = (CacheItem)obj;
        while (true)
        {
            try
            {
                saveDataFile(thisCache);
            }
            catch
            {

            }
            Thread.Sleep(thisCache.fileTime * 1000);//文件2分钟缓存
        }
    }

    public static Thread getThread(string threadName)
    {
        Thread tmpThread = null;
        lockx.EnterReadLock();
        try
        {
            if (threadTable.Keys.Contains(threadName))
            {
                tmpThread = threadTable[threadName];
            }
        }
        catch
        {
        }
        finally
        {
            lockx.ExitReadLock();
        }
        return tmpThread;
    }

    /// <summary>
    /// 添加缓存
    /// </summary>
    /// <param name="item">缓存对象</param>
    public static void saveCache(CacheItem item)
    {
        string mCacheName = item.CacheName + "_memory";
        string fCacheName = item.CacheName + "_file";
        Thread memoryCache = getThread(mCacheName);
        Thread fileCache = getThread(fCacheName);
        if (memoryCache == null)
        {
            memoryCache = new Thread(new ParameterizedThreadStart(UpdateCache));
            memoryCache.IsBackground = true;
            memoryCache.Start(item);
        }
        if (fileCache == null)
        {
            fileCache = new Thread(new ParameterizedThreadStart(UpdateFile));
            fileCache.IsBackground = true;
            fileCache.Start(item);
        }
        lockx.EnterWriteLock();
        try
        {
            threadTable[mCacheName] = memoryCache;
            threadTable[fCacheName] = fileCache;
        }
        catch { }
        finally { lockx.ExitWriteLock(); }
    }

    public static string readCacheContent(CacheItem item)
    {
        //Stopwatch watch = new Stopwatch();
        //watch.Start();
        string content = readCache(item.CacheName);
        if (content==null || content.Length < 0)
        {
            content = readFile(item.CacheName);
            saveCache(item);
        }
        //读取缓存失败
        if (content != null && content.Length <= 0)
        {
            //throw (new Exception("读取内容失败:" + item.CacheName));
            content = item.doProcess();
            //saveCache(item);
        }
        return content;
        //watch.Stop();
        //content += ("\r\n<!--方法执行时间:" + watch.ElapsedMilliseconds + "-->\r\n");
    }
    #endregion

    #region 公共处理
    public static string saveCache(string cacheName, ProcessDataDelegate mainMathod, object[] args)
    {
        using (CacheItem tmpCache = new CacheItem())
        {
            tmpCache.CacheName = cacheName;
            tmpCache.CacheDelegate = mainMathod;
            tmpCache.CacheArgs = args;
            string content = "";
            content = readCacheContent(tmpCache);
            return content;
        }
    }
    #endregion
}

 
现在给一个使用的例子:
 

view plaincopy to clipboardprint?
    #region 广告下文字链  
    public static string getTopAdList(params object[] args)   
    {  
        BeanOper oper = new BeanOper();  
        StringBuilder result = new StringBuilder();  
        result.Append("<div class=\"ad1\">");  
        result.Append("<ul>");  
        result.Append(oper.getAdNewsHtml(3519, 1, 9, "ad1_"));  
        result.Append("</ul>");  
        result.Append("<div class=\"clear\"></div>");  
        result.Append("</div>");  
        return result.ToString();  
    } 
    #endregion  
 
CacheSvr.saveCache("TopAdList", new CacheSvr.ProcessDataDelegate(IndexHtml.getTopAdList), new object[] { "" })