[ASP.NET揭密读书笔记]应用程序跟踪和监视

一、错误定向：
Two configuration settings affect how error information is displayed:

1.Custom errors mode— This setting enables or disables custom errors. When custom errors mode is enabled, errors on a page are hidden. This setting has three possible values: On, Off, and RemoteOnly.
When you are redirected to a page with custom errors, a query string variable is automatically passed to the error page. The query string variable, named aspxerrorpath, contains the path of the page that was originally requested.
2.Debug mode— When debug mode is enabled, additional information for debugging runtime errors is displayed.

例如如下的配置文件：
<configuration>
  <system.web>
    <customErrors mode="On" defaultRedirect="AppError.aspx">
      <error statusCode="404" redirect="NotFound.aspx" />
      <error statusCode="500" redirect="AppError.aspx" />
    </customErrors>
    <compilation debug="true" />
  </system.web>
</configuration>

二、使用性能计数器
1.Launch Performance Monitor by typing "perfmon" at a command prompt
2.Retrieving Performance Counters in an ASP.NET Page
You can use the classes from the System.Diagnostics namespace to work with performance counters within your application.
To retrieve an object that represents a particular performance counter, you need to supply the performance counter category name, performance counter name, and performance counter instance name. For example, the following statements create a counter that represents the Total Requests performance counter:
Dim objCounter As PerformanceCounter
objCounter = New PerformanceCounter( "ASP.NET Applications", "Requests Total", "__Total__" )

三、跟踪(Trace)页面执行
You can trace the execution of an ASP.NET page by using the trace attribute of the page directive. To enable tracing for a single ASP.NET page, include the following directive at the top of the page:<%@ Page Trace="True" %>。
When tracing is enabled for a page, trace information is automatically appended to the bottom of the page.
The trace information includes the following statistics:Request Details,Trace Information,Control Tree,Session State,Application State,Cookies Collection,Headers Collection,
Form Collection,QueryString Collection,Server Variables.

To add custom trace messages, use either the Trace.Warn or Trace.Write methods.
使用应用级别的Trace，You can use a special page, named trace.axd, to view trace information collected from all the pages in your application.
<configuration>
  <system.web>
  <trace
    enabled="true"
    requestLimit="50"
    pageOutput="false"
    traceMode="SortByTime"
    localOnly="true" />
  </system.web>
</configuration>
四、进程的监视
通过设置Machine.config中的某些项目可以修改aspnet_wp.exe的一些属性，例如memoryLimit— The percentage of system memory that the ASP.NET process is allowed to consume. By default, this setting has the value 80, which stands for 80% of system memory. (memoryLimit refers to the percentage of physical memory, not the percentage of virtual memory.)。其他还有requestQueueLimit，shutdownTimeout。
还可以在程序中获取当前进程的信息You can use the ProcessModelInfo class to retrieve information about the ASP.NET process. The GetCurrentProcessInfo method returns information about the ASP.NET process currently executing, and the GetProcessInfoHistory method returns a history of ASP.NET processes.