當(dāng)一個(gè)aspx頁(yè)面請(qǐng)求處理包括大量的IO工作,而這些IO資源又非常有限的情況下,那這個(gè)頁(yè)面在對(duì)面大量請(qǐng)求的時(shí)候就有可能導(dǎo)致大量線程等待處理,從而使應(yīng)用程序線程開銷過多影響整體的處理效能.在這種情況我們更希望通過一個(gè)隊(duì)列的機(jī)制控制處理線程的開銷來(lái)實(shí)現(xiàn)更高效的處理效能.因此.net提供IHttpAsyncHandler來(lái)解決這些事情,但有個(gè)問題就是實(shí)現(xiàn)一個(gè)IHttpAsyncHandler意味著要自己要實(shí)現(xiàn)自己的處理過程,并不能對(duì)已經(jīng)實(shí)現(xiàn)功能的.aspx進(jìn)行控制.但通過反編譯.net代碼來(lái)看可以實(shí)現(xiàn)一個(gè)IHttpAsyncHandler接管現(xiàn)有的.aspx頁(yè)面實(shí)現(xiàn)異步處理,又不需要修改現(xiàn)有頁(yè)面實(shí)現(xiàn)的代碼.下面詳細(xì)講述實(shí)現(xiàn)過
從.net的web配置文件來(lái)看asp.net默認(rèn)處理aspx的并不是IHttpHandler而是System.Web.UI.PageHandlerFactory,反編譯代碼看下
[PermissionSet(SecurityAction.InheritanceDemand, Unrestricted = true), PermissionSet(SecurityAction.LinkDemand, Unrestricted = true)]
public class PageHandlerFactory : IHttpHandlerFactory2, IHttpHandlerFactory
{
private bool _isInheritedInstance;
protected internal PageHandlerFactory()
{
this._isInheritedInstance = (base.GetType() != typeof(PageHandlerFactory));
}
public virtual IHttpHandler GetHandler(HttpContext context, string requestType, string virtualPath, string path)
{
return this.GetHandlerHelper(context, requestType, VirtualPath.CreateNonRelative(virtualPath), path);
}
IHttpHandler IHttpHandlerFactory2.GetHandler(HttpContext context, string requestType, VirtualPath virtualPath, string physicalPath)
{
if (this._isInheritedInstance)
{
return this.GetHandler(context, requestType, virtualPath.VirtualPathString, physicalPath);
}
return this.GetHandlerHelper(context, requestType, virtualPath, physicalPath);
}
public virtual void ReleaseHandler(IHttpHandler handler)
{
}
private IHttpHandler GetHandlerHelper(HttpContext context, string requestType, VirtualPath virtualPath, string physicalPath)
{
Page page = BuildManager.CreateInstanceFromVirtualPath(virtualPath, typeof(Page), context, true) as Page;
if (page == null)
{
return null;
}
page.TemplateControlVirtualPath = virtualPath;
return page;
}
}
從反編譯的代碼來(lái)看,看到的希望.首先PageHandlerFactory是可以繼承的,而GetHandler又是可重寫的,有了這兩個(gè)條件完全可以滿足我們的需要.通過承繼PageHandlerFactory就可以直接處理現(xiàn)有的aspx文件.
實(shí)現(xiàn)IHttpAsyncHandler
既然可以重寫PageHandlerFactory的GetHandler,而IhttpAsyncHandler又是繼承IHttpHandler;那事情就變得簡(jiǎn)單多了可能通過構(gòu)建一個(gè)IhttpAsyncHandler直接返回.
public class CustomPageFactory : System.Web.UI.PageHandlerFactory{
static CustomPageFactory()
{
G_TaskQueue = new TaskQueue(20);
}
public static TaskQueue G_TaskQueue;
public override IHttpHandler GetHandler(HttpContext context, string requestType, string virtualPath, string path)
{
AspxAsyncHandler handler = new AspxAsyncHandler(base.GetHandler(context, requestType, virtualPath, path));
return handler;
}
}
可以實(shí)現(xiàn)一個(gè)IHttpAsyncHandler把PageHandlerFactory返回的IHttpHandler重新包裝一下
public class AspxAsyncHandler : IHttpAsyncHandler{
public AspxAsyncHandler(IHttpHandler handler)
{
mHandler = handler;
}
private IHttpHandler mHandler;
public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
{
AspxAsyncResult result = new AspxAsyncResult(context, mHandler, cb);
CustomPageFactory.G_TaskQueue.Add(result);
return result;
}
public void EndProcessRequest(IAsyncResult result)
{
}
public bool IsReusable
{
get { return false; }
}
public void ProcessRequest(HttpContext context)
{
throw new NotImplementedException();
}
}
這樣一個(gè)異步處理的httphandler就包裝完了.我們只需要通過配置httphandler就可以實(shí)現(xiàn)對(duì)現(xiàn)有的aspx進(jìn)行異步隊(duì)列處理.
隊(duì)列和線程控制
在處理的過程中并沒有使用線程池來(lái)完成具體的工作,如果每個(gè)直接調(diào)用線程池那同樣面臨的問題就是線池線耗出現(xiàn)大量線程調(diào)度問題影響性能.所以在上面實(shí)現(xiàn)IHttpAsyncHandler的BeginProcessRequest方法中是構(gòu)建一個(gè)IAsyncResult添加到隊(duì)列中.之于這個(gè)隊(duì)列的實(shí)現(xiàn)相對(duì)比較簡(jiǎn)單:
public class TaskQueue{
public TaskQueue(int group)
{
mDispatchs = new List
for (int i = 0; i < group; i++)
{
mDispatchs.Add(new Dispatch());
}
}
private IList
private long mIndex = 0;
private int GetIndex()
{
return (int)System.Threading.Interlocked.Increment(ref mIndex) % mDispatchs.Count;
}
public void Add(AspxAsyncResult aspAsync)
{
if (aspAsync != null)
{
mDispatchs[GetIndex()].Push(aspAsync);
}
}
class Dispatch
{
public Dispatch()
{
System.Threading.ThreadPool.QueueUserWorkItem(OnRun);
}
private Queue
public void Push(AspxAsyncResult aspAR)
{
lock (this)
{
mQueue.Enqueue(aspAR);
}
}
private AspxAsyncResult Pop()
{
lock (this)
{
if (mQueue.Count > 0)
return mQueue.Dequeue();
return null;
}
}
private void OnRun(object state)
{
while (true)
{
AspxAsyncResult asyncResult = Pop();
if (asyncResult != null)
{
asyncResult.Execute();
}
else
{
System.Threading.Thread.Sleep(10);
}
}
}
}
}
為了更好地控制線程,隊(duì)列的實(shí)現(xiàn)是采用多隊(duì)列多線程機(jī)制,就是根據(jù)你需要的并發(fā)情況來(lái)指定線程隊(duì)列數(shù)來(lái)處理,當(dāng)然這種設(shè)計(jì)是比較死板并不靈活,如果想設(shè)計(jì)靈活一點(diǎn)是根據(jù)當(dāng)前隊(duì)列的處理情況和資源情況來(lái)動(dòng)態(tài)計(jì)算擴(kuò)沖現(xiàn)有隊(duì)列線程數(shù).
本文導(dǎo)航
- 第1頁(yè): 首頁(yè)
- 第2頁(yè): IAsyncResult實(shí)現(xiàn)
- 第3頁(yè): 測(cè)試效果和總結(jié)
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