记处理线上记录垃圾日志 The view 'Error' or its master was not found

最近监控线上日志，网站是ASP.NET MVC 开发的，发现不少错误日志都记录同样的内容：

The view ‘Error‘ or its master was not found or no view engine supports the searched locations. The following locations were searched:
~/Views/Search/Error.aspx
~/Views/Search/Error.ascx
~/Views/Shared/Error.aspx
~/Views/Shared/Error.ascx
~/Views/Search/Error.cshtml
~/Views/Search/Error.vbhtml
~/Views/Shared/Error.cshtml
~/Views/Shared/Error.vbhtml
System.Web.Mvc
   at System.Web.Mvc.ViewResult.FindView(ControllerContext context)

本地调试下不会发现，通过排查发现本地和线上配置的差异在于 customErrors mode="On"，将本地改后单点调试发现确实是将这样的错误记录，而本身我在action里面 throw 出来的异常已经抓取不到了。也就是说真的异常并未抓取到，而记录的是一个无关紧要莫名其妙的日志，因为我并没有任何代码去返回”Error“这个view。

先说下目前我抓取异常的方式：在Global.asax文件中增加

        protected void Application_Error(object sender, EventArgs e)
        {
            Exception ex = Server.GetLastError();
            //Write Log
        }

假如在Controller里面去override OnException方法进行写日志则不会出现这样的问题，但是在Controller里记日志可能会使在View里面出错的日志记录不到。

烦了很久，最后不经意发现MVC里面会默认注册一个Filter，代码如下

        public static void RegisterGlobalFilters(GlobalFilterCollection filters)
        {
            filters.Add(new HandleErrorAttribute());
        }

注册掉可以解决上述问题，但是我不太服气，于是在codeplex翻了mvc的源代码，HandleErrorAttribute的代码如下：

using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Web.Mvc.Properties;

namespace System.Web.Mvc
{
    [SuppressMessage("Microsoft.Performance", "CA1813:AvoidUnsealedAttributes", Justification = "This attribute is AllowMultiple = true and users might want to override behavior.")]
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
    public class HandleErrorAttribute : FilterAttribute, IExceptionFilter
    {
        private const string DefaultView = "Error";

        private readonly object _typeId = new object();

        private Type _exceptionType = typeof(Exception);
        private string _master;
        private string _view;

        public Type ExceptionType
        {
            get { return _exceptionType; }
            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException("value");
                }
                if (!typeof(Exception).IsAssignableFrom(value))
                {
                    throw new ArgumentException(String.Format(CultureInfo.CurrentCulture,
                                                              MvcResources.ExceptionViewAttribute_NonExceptionType, value.FullName));
                }

                _exceptionType = value;
            }
        }

        public string Master
        {
            get { return _master ?? String.Empty; }
            set { _master = value; }
        }

        public override object TypeId
        {
            get { return _typeId; }
        }

        public string View
        {
            get { return (!String.IsNullOrEmpty(_view)) ? _view : DefaultView; }
            set { _view = value; }
        }

        public virtual void OnException(ExceptionContext filterContext)
        {
            if (filterContext == null)
            {
                throw new ArgumentNullException("filterContext");
            }
            if (filterContext.IsChildAction)
            {
                return;
            }

            // If custom errors are disabled, we need to let the normal ASP.NET exception handler
            // execute so that the user can see useful debugging information.
            if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled)
            {
                return;
            }

            Exception exception = filterContext.Exception;

            // If this is not an HTTP 500 (for example, if somebody throws an HTTP 404 from an action method),
            // ignore it.
            if (new HttpException(null, exception).GetHttpCode() != 500)
            {
                return;
            }

            if (!ExceptionType.IsInstanceOfType(exception))
            {
                return;
            }

            string controllerName = (string)filterContext.RouteData.Values["controller"];
            string actionName = (string)filterContext.RouteData.Values["action"];
            HandleErrorInfo model = new HandleErrorInfo(filterContext.Exception, controllerName, actionName);
            filterContext.Result = new ViewResult
            {
                ViewName = View,
                MasterName = Master,
                ViewData = new ViewDataDictionary<HandleErrorInfo>(model),
                TempData = filterContext.Controller.TempData
            };
            filterContext.ExceptionHandled = true;
            filterContext.HttpContext.Response.Clear();
            filterContext.HttpContext.Response.StatusCode = 500;

            // Certain versions of IIS will sometimes use their own error page when
            // they detect a server error. Setting this property indicates that we
            // want it to try to render ASP.NET MVC‘s error page instead.
            filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;
        }
    }
}

HandleErrorAttribute

坑爹，他mvc里面会默认返回error视图，看来以后新开发时还是创建空项目好了。

至于为啥设置了customErrors mode="On"后才会出现这种垃圾日志，则要归咎于HandleErrorAttribute类的OnException方法里面了

        // If custom errors are disabled, we need to let the normal ASP.NET exception handler
            // execute so that the user can see useful debugging information.
            if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled)
            {
                return;
            }

解决方案是删掉默认注册的这个filter或者新增类去override相应的方法。

记处理线上记录垃圾日志 The view 'Error' or its master was not found