使用队列和线程对现有asp.net动态页处理进行资源控制

IIS可以对ASP.NET站点进行一个资源控制,包括使用的CPU,处理进程数等.但如果想对某些动态页面进行一个资源限制,只允许固定线程数量来处理某些动态请求,而不至于在某些情况个别的动态请求把整个站的资源都占光了.对于这么小的粒度控制显然不适合由IIS来做,这个时候就可以通过asp.net提供IHttpAsyncHandler来解决这种事情.

处理结构

由于Asp.net提供了异步处理Handler,所以可以在Handler的Begin处理方法中把具体对象存放到队列中,然后根据实际业务的需要来配置1-N个线程来处理相关请求.

IHttpAsyncHandler

public interface IHttpAsyncHandler : IHttpHandler
    {
        /// <summary>Initiates an asynchronous call to the HTTP handler.</summary>
        /// <returns>An <see cref="T:System.IAsyncResult" /> that contains information about the status of the process.</returns>
        /// <param name="context">An <see cref="T:System.Web.HttpContext" /> object that provides references to intrinsic server objects (for example, Request, Response, Session, and Server) used to service HTTP requests. </param>
        /// <param name="cb">The <see cref="T:System.AsyncCallback" /> to call when the asynchronous method call is complete. If <paramref name="cb" /> is null, the delegate is not called. </param>
        /// <param name="extraData">Any extra data needed to process the request. </param>
        IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData);
        /// <summary>Provides an asynchronous process End method when the process ends.</summary>
        /// <param name="result">An <see cref="T:System.IAsyncResult" /> that contains information about the status of the process. </param>
        void EndProcessRequest(IAsyncResult result);
    }

从代码来看IHttpAsyncHandler也是从IHttpHandler派生下来,并提供了Begin和End相关方法.

对已有页面进行异步封装

如果经常用IHttpHandler的朋友应该比较清楚这东西用于描述一个页面请求的,包括我们的aspx,而aspx默认处理的则是一个IHttpHandlerFactory实现System.Web.UI.PageHandlerFactory.通简单地继承System.Web.UI.PageHandlerFactory就可以让原来的aspx请求返回对应的异步的HttpHandler.

public class CustomPageFactory : System.Web.UI.PageHandlerFactory
    {
        static CustomPageFactory()
        {
            
        }
        
        public override IHttpHandler GetHandler(HttpContext context, string requestType, string virtualPath, string path)
        {
            AspxAsyncHandler handler = new AspxAsyncHandler(base.GetHandler(context, requestType, virtualPath, path));
            return handler;
        }
    }

PageFactory实现后只需要简单地配置一个web.config文件就可以让现有的aspx处理由异步Handler来处理.

<handlers>
   <add name="custompage" verb="*" path="*.aspx" type="WebApp.Code.CustomPageFactory,WebApp"/>
</handlers>

队列化处理

制定队列的目的非常简单就是有序可控地去处理一些工作,可以通过BeginProcessRequest的执行把请求先存放到了列中

public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
        {
            AspxAsyncResult result = new AspxAsyncResult(context, mHandler, cb);
            G_TaskQueue.Add(result);
            return result;
        }

制定线程处理

可以根据实际情况开启1-N个线程来处理队列中的工作.

private void OnRun(object state)
        {
                while (true)
                {
                    AspxAsyncResult asyncResult = Pop();
                    if (asyncResult != null)
                    {
                        asyncResult.Execute();
                    }
                    else
                    {
                        System.Threading.Thread.Sleep(10);
                    }
                }
        }