Unity和Random"索引超出了数组的范围"异常

Question

我们运行的网站有大约15.000个实时用户(谷歌分析)(大约1000个请求/秒(性能计数器)).

我们有两个Web服务器后面的负载均衡器.

有时每天有时每周一次我们的Web服务器停止执行请求并开始响应错误,每个请求都记录异常:"System.IndexOutOfRangeException - Index超出了数组的范围."

我们的环境:IIS 8.5,.Net 4.5.0,Mvc 5.1.0,Unity 3.5(与3.0相同),WebActivatorEx 2.0在IIS中,工作进程1和其他设置具有默认值.

我们无法捕捉到任何特定情况造成此错误.应用程序池回收后,一切都没有问题.在每个请求响应错误之前,没有任何与之相关的错误.

过去有一个问题与相关的旧Unity版本有关:https : //unity.codeplex.com/discussions/328841 http://unity.codeplex.com/workitem/11791 看不到我能做些什么.

这里有异常细节:

System.IndexOutOfRangeException
Index was outside the bounds of the array.

System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Microsoft.Practices.Unity.NamedTypesRegistry.RegisterType(Type t, String name)
   at Microsoft.Practices.Unity.UnityDefaultBehaviorExtension.OnRegisterInstance(Object sender, RegisterInstanceEventArgs e)
   at System.EventHandler`1.Invoke(Object sender, TEventArgs e)
   at Microsoft.Practices.Unity.UnityContainer.RegisterInstance(Type t, String name, Object instance, LifetimeManager lifetime)
   at Microsoft.Practices.Unity.UnityContainerExtensions.RegisterInstance[TInterface](IUnityContainer container, TInterface instance, LifetimeManager lifetimeManager)
   at DemoSite.News.Portal.UI.App_Start.UnityConfig.<>c__DisplayClass1.<RegisterTypes>b__0()
   at DemoSite.News.Portal.Core.Controller.BaseController.Initialize(RequestContext requestContext)
   at System.Web.Mvc.Controller.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state)
   at System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__4(AsyncCallback asyncCallback, Object asyncState, ProcessRequestState innerState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallBeginDelegate(AsyncCallback callback, Object callbackState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout)
   at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TState](AsyncCallback callback, Object callbackState, BeginInvokeDelegate`1 beginDelegate, EndInvokeVoidDelegate`1 endDelegate, TState invokeState, Object tag, Int32 timeout, SynchronizationContext callbackSyncContext)
   at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

我的配置如下:

public static void RegisterTypes(IUnityContainer container) 
{ 
    var section = (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
    container.LoadConfiguration(section); 
    ServiceLocator.SetLocatorProvider(() => new UnityServiceLocator(container));
}

初始化方法如下:

protected override void Initialize(System.Web.Routing.RequestContext requestContext)
{
    if (requestContext.RouteData.Values["ViewActionId"] != null)
    {
        int viewActionId;
        if (!int.TryParse(requestContext.RouteData.Values["ViewActionId"].ToString(), out viewActionId))
            return;

        var cacheProvider = ServiceLocator.Current.GetInstance<ICacheProvider>();
        List<ViewActionClass> viewActionClasses = null;
        string cacheKey = CacheKeyCompute.ComputeCacheKey("ViewActionClass", CacheKeyTypes.DataCache,
            new KeyValuePair<string, string>("viewActionId", viewActionId.ToString()));

        _configuration = ServiceLocator.Current.GetInstance<IConfiguration>();

        viewActionClasses = 
            cacheProvider.AddOrGetExistingWithLock<List<ViewActionClass>>(cacheKey, () =>
        {
            var viewActionClassBusiness = 
            ServiceLocator.Current.GetInstance<IViewActionClassBusiness>();

            return viewActionClassBusiness.ViewActionClassGetByViewActionId(viewActionId);
        });

        ViewBag.ActionClass = viewActionClasses;
        ViewBag.Configuration = _configuration;
    }
    base.Initialize(requestContext);
}

注册xml for ICacheProvider,IConfiguration和IViewActionClassBusiness

<type type="DemoSite.Runtime.Caching.ICacheProvider, DemoSite.Core"
        mapTo="DemoSite.Runtime.Caching.ObjectCacheProvider, DemoSite.Core">
    <lifetime type="containerControlledLifetimeManager" />
  </type>
<type type="DemoSite.Core.Configuration.IConfiguration, DemoSite.Core"
        mapTo="DemoSite.Core.Configuration.ConfigFileConfiguration, DemoSite.Core">
    <lifetime type="containerControlledLifetimeManager" />
  </type>
<type type="DemoSite.News.Business.IViewActionClassBusiness, DemoSite.News.Business"
        mapTo="DemoSite.News.Business.Default.ViewActionClassBusiness, DemoSite.News.Business.Default">
    <lifetime type="perRequestLifetimeManager" />
  </type>

也许它与高流量有关.是否有人遇到类似的问题和任何解决方案？

提前致谢

Answer 1

从堆栈跟踪中我可以看到,您在Web请求期间在容器中注册实例.这些RegisterType和RegisterInstance方法在Unity 中不是线程安全的(这可能适用于.NET中的大多数DI库).这就解释了为什么这种情况发生在随机点和高负荷下.

最好只在启动时注册容器,以后不要更改容器.特别是使用依赖性倒置原则和依赖性注入模式,您可以集中处理对象图如何连接的知识,但是稍后通过执行新的注册将其再次分散.即使注册对Unity是线程安全的,你仍然很可能通过在运行时更改注册来引入竞争条件.

UPDATE

您的代码具有以下导致问题的代码:

ServiceLocator.SetLocatorProvider(() => new UnityServiceLocator(container));

这看起来很无辜,但实际上它会导致并发错误和内存泄漏.

因为new语句在lambda中,所以UnityServiceLocator每次调用时都会创建一个new ServiceLocator.Current.这本身并不坏,但是UnityServiceLocator构造函数调用container.RegisterInstance它来在容器中注册自己.但正如我已经说过的那样:调用RegisterInstance`不是线程安全的.

但即使它是线程安全的,它仍会导致应用程序中的内存泄漏,因为调用RegisterInstance不会替换现有注册,而是将其附加到注册列表中.这意味着UnityServiceLocator容器中的实例列表将继续增长,并最终导致系统崩溃并出现OutOfMemoryException.你真的很幸运,你首先遇到这个并发错误,因为OOM错误将更难追溯.

修复实际上非常简单:移动UnityServiceLocatorlambda 的构造并每次返回该单个实例:

var locator = new UnityServiceLocator(container);
ServiceLocator.SetLocatorProvider(() => locator);

UnityServiceLocator在我看来,这是一个设计缺陷的行为,因为因为RegisterInstance它不是线程安全的,UnityServiceLocator并且不知道它创建了多少次,所以它永远不应该RegisterInstance从它的构造函数中调用- 或者至少 - 不是没有检查是否注册该实例是安全的.

然而问题是删除该调用RegisterInstance是一个重大变化,但仍然可能是Unity团队的最佳解决方案.大多数用户可能不会注意到丢失的IServiceLocator注册,如果他们这样做,Unity将在这种情况下传达明确的异常消息.另一种选择是UnityServiceLocator检查是否已经从容器中解析了任何实例,并且在这种情况下从UnityServiceLocator构造函数中抛出InvalidOperationException .