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[转载]ASP.NET性能优化之构建自定义文件缓存 – 陆敏技 – 博客园.
SP.NET的输出缓存（即静态HTML）在.NET4.0前一直是基于内存的。这意味着如果我们的站点含有大量的缓存，则很容易消耗掉本机内存。 现在，借助于.NET4.0中的OutputCacheProvider，我们可以有多种选择创建自己的缓存。如，我们可以把HTML输出缓存存储到 memcached分布式集群服务器，或者MongoDB中（一种常用的面向文档数据库，不妨阅读本篇http://msdn.microsoft.com/zh-cn/magazine/gg650661.aspx）。当然，我们也可以把缓存作为文件存储到硬盘上，考虑到可扩展性，这是一种最廉价的做法，本文就是介绍如果构建自定义文件缓存。
1：OutputCacheProvider
OutputCacheProvider是一个抽象基类，我们需要override其中的四个方法，它们分别是：
Add 方法，将指定项插入输出缓存中。
Get 方法，返回对输出缓存中指定项的引用。
Remove 方法，从输出缓存中移除指定项。
Set 方法，将指定项插入输出缓存中，如果该项已缓存，则覆盖该项。
2：创建自己的文件缓存处理类
该类型为FileCacheProvider，代码如下：
<span class="kwd">public</span><span class="pln"> </span><span class="kwd">class</span><span class="pln"> </span><span class="typ">FileCacheProvider</span><span class="pln"> </span><span class="pun">:</span><span class="pln"> </span><span class="typ">OutputCacheProvider</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">private</span><span class="pln"> </span><span class="kwd">static</span><span class="pln"> </span><span class="kwd">readonly</span><span class="pln"> </span><span class="typ">ILog</span><span class="pln"> log </span><span class="pun">=</span><span class="pln"> </span><span class="typ">LogManager</span><span class="pun">.</span><span class="typ">GetLogger</span><span class="pun">(</span><span class="typ">System</span><span class="pun">.</span><span class="typ">Reflection</span><span class="pun">.</span><span class="typ">MethodBase</span><span class="pun">.</span><span class="typ">GetCurrentMethod</span><span class="pun">().</span><span class="typ">DeclaringType</span><span class="pun">);</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">override</span><span class="pln"> </span><span class="kwd">void</span><span class="pln"> </span><span class="typ">Initialize</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> name</span><span class="pun">,</span><span class="pln"> </span><span class="typ">NameValueCollection</span><span class="pln"> attributes</span><span class="pun">)</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">base</span><span class="pun">.</span><span class="typ">Initialize</span><span class="pun">(</span><span class="pln">name</span><span class="pun">,</span><span class="pln"> attributes</span><span class="pun">);</span><span class="pln"></span><span class="typ">CachePath</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="typ">HttpContext</span><span class="pun">.</span><span class="typ">Current</span><span class="pun">.</span><span class="typ">Server</span><span class="pun">.</span><span class="typ">MapPath</span><span class="pun">(</span><span class="pln">attributes</span><span class="pun">[</span><span class="str">"cachePath"</span><span class="pun">]);</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">override</span><span class="pln"> </span><span class="kwd">object</span><span class="pln"> </span><span class="typ">Add</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> key</span><span class="pun">,</span><span class="pln"> </span><span class="kwd">object</span><span class="pln"> entry</span><span class="pun">,</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pln"> utcExpiry</span><span class="pun">)</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="typ">Object</span><span class="pln"> obj </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Get</span><span class="pun">(</span><span class="pln">key</span><span class="pun">);</span><span class="pln"></span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">obj </span><span class="pun">!=</span><span class="pln"> </span><span class="kwd">null</span><span class="pun">)</span><span class="pln"> </span><span class="com">//这一步很重要</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> obj</span><span class="pun">;</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="typ">Set</span><span class="pun">(</span><span class="pln">key</span><span class="pun">,</span><span class="pln">entry</span><span class="pun">,</span><span class="pln">utcExpiry</span><span class="pun">);</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> entry</span><span class="pun">;</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">override</span><span class="pln"> </span><span class="kwd">object</span><span class="pln"> </span><span class="typ">Get</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> key</span><span class="pun">)</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">string</span><span class="pln"> path </span><span class="pun">=</span><span class="pln"> </span><span class="typ">ConvertKeyToPath</span><span class="pun">(</span><span class="pln">key</span><span class="pun">);</span><span class="pln"></span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(!</span><span class="typ">File</span><span class="pun">.</span><span class="typ">Exists</span><span class="pun">(</span><span class="pln">path</span><span class="pun">))</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">null</span><span class="pun">;</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="typ">CacheItem</span><span class="pln"> item </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">null</span><span class="pun">;</span><span class="pln"></span><span class="kwd">using</span><span class="pln"> </span><span class="pun">(</span><span class="typ">FileStream</span><span class="pln"> file </span><span class="pun">=</span><span class="pln"> </span><span class="typ">File</span><span class="pun">.</span><span class="typ">OpenRead</span><span class="pun">(</span><span class="pln">path</span><span class="pun">))</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">var</span><span class="pln"> formatter </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">BinaryFormatter</span><span class="pun">();</span><span class="pln">item </span><span class="pun">=</span><span class="pln"> </span><span class="pun">(</span><span class="typ">CacheItem</span><span class="pun">)</span><span class="pln">formatter</span><span class="pun">.</span><span class="typ">Deserialize</span><span class="pun">(</span><span class="pln">file</span><span class="pun">);</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">item</span><span class="pun">.</span><span class="typ">ExpiryDate</span><span class="pln"> </span><span class="pun">&</span><span class="pln">lt</span><span class="pun">;=</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pun">.</span><span class="typ">Now</span><span class="pun">.</span><span class="typ">ToUniversalTime</span><span class="pun">())</span><span class="pln"></span><span class="pun">{</span><span class="pln">log</span><span class="pun">.</span><span class="typ">Info</span><span class="pun">(</span><span class="pln">item</span><span class="pun">.</span><span class="typ">ExpiryDate</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> </span><span class="str">"*"</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> key</span><span class="pun">);</span><span class="pln"></span><span class="typ">Remove</span><span class="pun">(</span><span class="pln">key</span><span class="pun">);</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">null</span><span class="pun">;</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> item</span><span class="pun">.</span><span class="typ">Item</span><span class="pun">;</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">override</span><span class="pln"> </span><span class="kwd">void</span><span class="pln"> </span><span class="typ">Set</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> key</span><span class="pun">,</span><span class="pln"> </span><span class="kwd">object</span><span class="pln"> entry</span><span class="pun">,</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pln"> utcExpiry</span><span class="pun">)</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="typ">CacheItem</span><span class="pln"> item </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">CacheItem</span><span class="pun">(</span><span class="pln">entry</span><span class="pun">,</span><span class="pln"> utcExpiry</span><span class="pun">);</span><span class="pln"></span><span class="kwd">string</span><span class="pln"> path </span><span class="pun">=</span><span class="pln"> </span><span class="typ">ConvertKeyToPath</span><span class="pun">(</span><span class="pln">key</span><span class="pun">);</span><span class="pln"></span><span class="kwd">using</span><span class="pln"> </span><span class="pun">(</span><span class="typ">FileStream</span><span class="pln"> file </span><span class="pun">=</span><span class="pln"> </span><span class="typ">File</span><span class="pun">.</span><span class="typ">OpenWrite</span><span class="pun">(</span><span class="pln">path</span><span class="pun">))</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="typ">BinaryFormatter</span><span class="pln"> formatter </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">BinaryFormatter</span><span class="pun">();</span><span class="pln">formatter</span><span class="pun">.</span><span class="typ">Serialize</span><span class="pun">(</span><span class="pln">file</span><span class="pun">,</span><span class="pln"> item</span><span class="pun">);</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">override</span><span class="pln"> </span><span class="kwd">void</span><span class="pln"> </span><span class="typ">Remove</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> key</span><span class="pun">)</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">string</span><span class="pln"> path </span><span class="pun">=</span><span class="pln"> </span><span class="typ">ConvertKeyToPath</span><span class="pun">(</span><span class="pln">key</span><span class="pun">);</span><span class="pln"></span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="typ">File</span><span class="pun">.</span><span class="typ">Exists</span><span class="pun">(</span><span class="pln">path</span><span class="pun">))</span><span class="pln"></span><span class="typ">File</span><span class="pun">.</span><span class="typ">Delete</span><span class="pun">(</span><span class="pln">path</span><span class="pun">);</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">string</span><span class="pln"> </span><span class="typ">CachePath</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">get</span><span class="pun">;</span><span class="pln"></span><span class="kwd">set</span><span class="pun">;</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">private</span><span class="pln"> </span><span class="kwd">string</span><span class="pln"> </span><span class="typ">ConvertKeyToPath</span><span class="pun">(</span><span class="kwd">string</span><span class="pln"> key</span><span class="pun">)</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">string</span><span class="pln"> file </span><span class="pun">=</span><span class="pln"> key</span><span class="pun">.</span><span class="typ">Replace</span><span class="pun">(</span><span class="str">'/'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'-'</span><span class="pun">);</span><span class="pln">file </span><span class="pun">+=</span><span class="pln"> </span><span class="str">".txt"</span><span class="pun">;</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> </span><span class="typ">Path</span><span class="pun">.</span><span class="typ">Combine</span><span class="pun">(</span><span class="typ">CachePath</span><span class="pun">,</span><span class="pln"> file</span><span class="pun">);</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="pun">[</span><span class="typ">Serializable</span><span class="pun">]</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">class</span><span class="pln"> </span><span class="typ">CacheItem</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pln"> </span><span class="typ">ExpiryDate</span><span class="pun">;</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">object</span><span class="pln"> </span><span class="typ">Item</span><span class="pun">;</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="typ">CacheItem</span><span class="pun">(</span><span class="kwd">object</span><span class="pln"> entry</span><span class="pun">,</span><span class="pln"> </span><span class="typ">DateTime</span><span class="pln"> utcExpiry</span><span class="pun">)</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="typ">Item</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> entry</span><span class="pun">;</span><span class="pln"></span><span class="typ">ExpiryDate</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> utcExpiry</span><span class="pun">;</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="pun">}</span> |
有两个地方需要特别说明：
在Add方法中，有一个条件判断，必须做出这样的处理，否则缓存机制将会缓存第一次的结果，过了有效期后缓存讲失效并不再重建；
在示例程序中，我们简单的将缓存放到了Cache目录下，在实际的项目实践中，考虑到缓存的页面将是成千上万的，所以我们必须要做目录分级，否则寻找并读取缓存文件将会成为效率瓶颈，这会耗尽CPU。
3：配置文件
我们需要在Web.config中配置缓存处理程序是自定义的FileCacheProvider，即在 <system.web>下添加节点：
4：缓存的使用
我们假设在MVC的控制中使用（如果要在ASP.NET页面中使用，则在页面中包含<%@OutputCache VaryByParam=”none” Duration=”10″ %>），可以看到，Index是未进行输出缓存的，而Index2进行了输出缓存，缓存时间为10秒。
<span class="kwd">public</span><span class="pln"> </span><span class="kwd">class</span><span class="pln"> </span><span class="typ">HomeController</span><span class="pln"> </span><span class="pun">:</span><span class="pln"> </span><span class="typ">Controller</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">private</span><span class="pln"> </span><span class="kwd">static</span><span class="pln"> </span><span class="kwd">readonly</span><span class="pln"> </span><span class="typ">ILog</span><span class="pln"> log </span><span class="pun">=</span><span class="pln"> </span><span class="typ">LogManager</span><span class="pun">.</span><span class="typ">GetLogger</span><span class="pun">(</span><span class="typ">System</span><span class="pun">.</span><span class="typ">Reflection</span><span class="pun">.</span><span class="typ">MethodBase</span><span class="pun">.</span><span class="typ">GetCurrentMethod</span><span class="pun">().</span><span class="typ">DeclaringType</span><span class="pun">);</span><span class="pln"></span><span class="kwd">static</span><span class="pln"> </span><span class="kwd">string</span><span class="pln"> s_conn </span><span class="pun">=</span><span class="pln"> </span><span class="str">"Data Source=192.168.0.77;Initial Catalog=luminjidb;User Id=sa;Password=sa;"</span><span class="pun">;</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="typ">ActionResult</span><span class="pln"> </span><span class="typ">Index</span><span class="pun">()</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">using</span><span class="pln"> </span><span class="pun">(</span><span class="typ">DataSet</span><span class="pln"> ds </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Common</span><span class="pun">.</span><span class="typ">SqlHelper</span><span class="pun">.</span><span class="typ">ExecuteDataset</span><span class="pun">(</span><span class="pln">s_conn</span><span class="pun">,</span><span class="pln"> </span><span class="typ">CommandType</span><span class="pun">.</span><span class="typ">Text</span><span class="pun">,</span><span class="pln"> </span><span class="str">"select top 1* from NameTb a, DepTb b where a.DepID = b.ID ORDER BY NEWID()"</span><span class="pun">))</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="typ">ViewBag</span><span class="pun">.</span><span class="typ">Message</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> ds</span><span class="pun">.</span><span class="typ">Tables</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class="typ">Rows</span><span class="pun">[</span><span class="lit">0</span><span class="pun">][</span><span class="str">"name"</span><span class="pun">].</span><span class="typ">ToString</span><span class="pun">();</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> </span><span class="typ">View</span><span class="pun">();</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="pun">[</span><span class="typ">OutputCache</span><span class="pun">(</span><span class="typ">Duration</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="lit">10</span><span class="pun">,</span><span class="pln"> </span><span class="typ">VaryByParam</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="str">"none"</span><span class="pun">)]</span><span class="pln"></span><span class="kwd">public</span><span class="pln"> </span><span class="typ">ActionResult</span><span class="pln"> </span><span class="typ">Index2</span><span class="pun">()</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="kwd">using</span><span class="pln"> </span><span class="pun">(</span><span class="typ">DataSet</span><span class="pln"> ds </span><span class="pun">=</span><span class="pln"> </span><span class="typ">Common</span><span class="pun">.</span><span class="typ">SqlHelper</span><span class="pun">.</span><span class="typ">ExecuteDataset</span><span class="pun">(</span><span class="pln">s_conn</span><span class="pun">,</span><span class="pln"> </span><span class="typ">CommandType</span><span class="pun">.</span><span class="typ">Text</span><span class="pun">,</span><span class="pln"> </span><span class="str">"select top 1* from NameTb a, DepTb b where a.DepID = b.ID ORDER BY NEWID()"</span><span class="pun">))</span><span class="pln"></span><span class="pun">{</span><span class="pln"></span><span class="typ">ViewBag</span><span class="pun">.</span><span class="typ">Message</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> ds</span><span class="pun">.</span><span class="typ">Tables</span><span class="pun">[</span><span class="lit">0</span><span class="pun">].</span><span class="typ">Rows</span><span class="pun">[</span><span class="lit">0</span><span class="pun">][</span><span class="str">"name"</span><span class="pun">].</span><span class="typ">ToString</span><span class="pun">();</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="kwd">return</span><span class="pln"> </span><span class="typ">View</span><span class="pun">();</span><span class="pln"></span><span class="pun">}</span><span class="pln"></span><span class="pun">}</span> |
5：查看下效果
上面的代码，在访问了Index2后，将会在Cache文件夹下产生缓存文件，如下：
现在，我们开始评价下有输出缓存和无输出缓存的性能对比，模拟100个用户并发1000次请求如下：
可以看到，有输出缓存后，吞吐率明显提高了10倍。
6：代码下载
FileCacheProvider的原始代码来自于网络，我修改了其中的BUG，全部代码下载如下：MvcApplication20110907.rar
