SDL web8.1.1 Could not execute query Sdl.Web.Delivery.Service.ServiceQueryException (Sdl.Web.Delivery.Service) - Failed to execute query

Question

We have upgraded from Tridion 2013 SP1 + DD4T 1.0 to SDL Web 8.1.1 micro services + DD4T 2.0 + SDL Web8 CIL proivder

Summary of the issue - Initially, we did upgrade SDL Web 8.1.1 + DD4T 2.0 legacy method without micro services, we had a CPU spikes issue it was working fine everything as expected but some behaviour, for example, 100times or 1000 times working fine and then some trigger trying to execute broker query or taxonomy keyword meta query CPU goes high not coming down because of that website goes down. - The following action items were done to investigated took the crash dump file during the CPU high to find out the route cast in the IIS worker app pool in process java JVM objects takes High CPU also noticed private memory also increasing from ~2GB to ~6GB

• And then decided to upgraded to micro-services, and then CPU issue was gone but we are getting now new issue very often getting this below error message and website getting 500 Internal server error.

None of the database broker database queries was succedded, we also noticed broker databse CPU was normal at the time.

06:48:49.29  Error    Handle Section At Error occured at HandleSectionErrorAttribute handling - Error occured at

Sdl.Web.Delivery.Service.AbstractODataService : HandleException and Handling (http://www.sharjah24.ae/ar/uae/209359-%D8%AF%D9%8A%D9%88%D8%A7%D9%86-%D8%AD%D8%A7%D9%83%D9%85-%D8%A7%D9%84%D9%81%D8%AC%D9%8A%D8%B1%D8%A9-%D9%8A%D9%86%D8%B9%D9%89-%D8%A7%D9%84%D9%85%D8%BA%D9%81%D9%88%D8%B1-%D9%84%D9%87-%D8%B3%D9%85%D9%88-%D8%A7%D9%84%D8%B4%D9%8A%D8%AE-%D8%AD%D9%85%D8%AF-%D8%A8%D9%86-%D8%B3%D9%8A%D9%81-%D8%A7%D9%84%D8%B4%D8%B1%D9%82%D9%8A by 162.158.78.40) ... Sdl.Web.Delivery.Service.ServiceQueryException (Sdl.Web.Delivery.Service) ... Failed to execute query ... at Sdl.Web.Delivery.Service.AbstractODataService.HandleException(Exception e) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_01.<Execute>b__0() ... at Sdl.Web.Delivery.Service.Utils.PerformRetry[T](Func1 block, Int32 retryCount) ... at Sdl.Web.Delivery.Service.Utils.Retry[T](Func1 block, Int32 retryCount, Boolean locking) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.ExecuteComponentPresentationMetaDAOMethod(Int32 publicationId, String methodName, Object[] parameters) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.GetComponentPresentationWithHighestPriority(Int32 componentId) ... at Indivirtual.SHARJAH24.Common.TridionComponentPresentationProvider.GetContent(String uri, String templateUri) ... at DD4T.Factories.ComponentPresentationFactory.TryGetComponentPresentation(IComponentPresentation& cp, String componentUri, String templateUri) ... at DD4T.Factories.ComponentFactory.TryGetComponent(String componentUri, IComponent& component, String templateUri) ... at Indivirtual.DD4T.Mvc.Controllers.BasePageController.GetModelForPage(String PageId, PageType type) ... at Indivirtual.SHARJAH24.Controllers.PageController.Page(String pageId) ... at lambda_method(Closure , ControllerBase , Object[] ) ... at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) ... at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) ... at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult2.CallEndDelegate(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.b__3d() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.b__1c() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.b__1e(IAsyncResult asyncResult) ... System.NullReferenceException (Microsoft.OData.Client) ... Object reference not set to an instance of an object. ... at Microsoft.OData.Client.ClientEdmModel.<>c__DisplayClass19.b__d(IEdmSchemaElement et) ... at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable1 source, Func2 predicate) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmTypeInternal(IEdmStructuredType edmBaseType, Type type, PropertyInfo[] keyProperties, Boolean isEntity, Nullable1 hasProperties) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmType(Type type) ... at Microsoft.OData.Client.DataServiceContext.IsSingletonType[TElement]() ... at Microsoft.OData.Client.DataServiceContext.Execute[TElement](Uri requestUri, String httpMethod, OperationParameter[] operationParameters) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_11.b__1() ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_01.<Execute>b__0() ...
06:48:49.30 Error Timestamp 02-Apr-2017 06:48:44 06:48:49.30 Error Machine SMC-WWW2 06:48:49.30 Error Useragent Mozilla/5.0 (compatible; linkdexbot/2.2; +http://www.linkdex.com/bots/) 06:48:49.30 Error Client 162.158.78.40 (162.158.78.40) 06:48:49.30 Error Referrer
06:48:50.07 Error {0}: Could not execute query ... Sdl.Web.Delivery.Service.ServiceQueryException (Sdl.Web.Delivery.Service) ... Failed to execute query ... at Sdl.Web.Delivery.Service.AbstractODataService.HandleException(Exception e) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_01.b__0() ... at Sdl.Web.Delivery.Service.Utils.PerformRetry[T](Func1 block, Int32 retryCount) ... at Sdl.Web.Delivery.Service.Utils.Retry[T](Func1 block, Int32 retryCount, Boolean locking) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.ExecuteComponentPresentationMetaDAOMethod(Int32 publicationId, String methodName, Object[] parameters) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.GetComponentPresentationWithHighestPriority(Int32 componentId) ... at Indivirtual.SHARJAH24.Common.TridionComponentPresentationProvider.GetContent(String uri, String templateUri) ... at DD4T.Factories.ComponentPresentationFactory.TryGetComponentPresentation(IComponentPresentation& cp, String componentUri, String templateUri) ... at DD4T.Factories.ComponentFactory.TryGetComponent(String componentUri, IComponent& component, String templateUri) ... at Indivirtual.DD4T.Tridion.Broker.BrokerQuery.<>c.b__22_2(String c) ... at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext() ... at System.Linq.Enumerable.WhereEnumerableIterator1.MoveNext() ... at System.Collections.Generic.List1..ctor(IEnumerable1 collection) ... at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) ... at Indivirtual.DD4T.Tridion.Broker.BrokerQuery.Execute(Int32 pageIndex, Int32 pageSize) ... System.NullReferenceException (Microsoft.OData.Client) ... Object reference not set to an instance of an object. ... at Microsoft.OData.Client.ClientEdmModel.<>c__DisplayClass19.<GetOrCreateEdmTypeInternal>b__d(IEdmSchemaElement et) ... at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable1 source, Func2 predicate) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmTypeInternal(IEdmStructuredType edmBaseType, Type type, PropertyInfo[] keyProperties, Boolean isEntity, Nullable1 hasProperties) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmType(Type type) ... at Microsoft.OData.Client.DataServiceContext.IsSingletonTypeTElement ... at Microsoft.OData.Client.DataServiceContext.Execute[TElement](Uri requestUri, String httpMethod, OperationParameter[] operationParameters) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_11.<Execute>b__1() ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_01.b__0() ...
06:48:50.07 Error Handle Section At Error occured at HandleSectionErrorAttribute handling - Error occured at System.Linq.Enumerable : FirstOrDefault and Handling (http://www.sharjah24.ae/ar/ by 162.158.92.166) ... System.ArgumentNullException (System.Core) ... Value cannot be null. ... Parameter name: source ... at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable1 source, Func2 predicate) ... at Indivirtual.SHARJAH24.Model.ModelExtension.MainArticles(IPage page, Int32 mainArticleCount, Boolean populateAuthors) ... at Indivirtual.SHARJAH24.Controllers.PageController.GetIndexModel(IPage page) ... at Indivirtual.SHARJAH24.Controllers.PageController.GetView(IPage page) ... at Indivirtual.SHARJAH24.Controllers.PageController.Page(String pageId) ... at lambda_method(Closure , ControllerBase , Object[] ) ... at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) ... at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) ... at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult2.CallEndDelegate(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) ...
06:48:50.07 Error Timestamp 02-Apr-2017 06:48:45 06:48:50.07 Error Machine SMC-WWW2 06:48:50.07 Error Useragent Mozilla/5.0 (Windows NT 6.1; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0 06:48:50.07 Error Client 162.158.92.166 (162.158.92.166) 06:48:50.07 Error Referrer
06:48:57.05 Error Handle Section At Error occured at HandleSectionErrorAttribute handling - Error occured at Sdl.Web.Delivery.Service.AbstractODataService : HandleException and Handling (http://www.sharjah24.ae/ar/sports/international/198729- by 141.101.76.154) ... Sdl.Web.Delivery.Service.ServiceQueryException (Sdl.Web.Delivery.Service) ... Failed to execute query ... at Sdl.Web.Delivery.Service.AbstractODataService.HandleException(Exception e) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_01.b__0() ... at Sdl.Web.Delivery.Service.Utils.PerformRetry[T](Func1 block, Int32 retryCount) ... at Sdl.Web.Delivery.Service.Utils.Retry[T](Func1 block, Int32 retryCount, Boolean locking) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.ExecuteComponentPresentationMetaDAOMethod(Int32 publicationId, String methodName, Object[] parameters) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.GetComponentPresentationWithHighestPriority(Int32 componentId) ... at Indivirtual.SHARJAH24.Common.TridionComponentPresentationProvider.GetContent(String uri, String templateUri) ... at DD4T.Factories.ComponentPresentationFactory.TryGetComponentPresentation(IComponentPresentation& cp, String componentUri, String templateUri) ... at DD4T.Factories.ComponentFactory.TryGetComponent(String componentUri, IComponent& component, String templateUri) ... at Indivirtual.DD4T.Mvc.Controllers.BasePageController.GetModelForPage(String PageId, PageType type) ... at Indivirtual.SHARJAH24.Controllers.PageController.Page(String pageId) ... at lambda_method(Closure , ControllerBase , Object[] ) ... at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) ... at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) ... at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult2.CallEndDelegate(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) ... System.NullReferenceException (Microsoft.OData.Client) ... Object reference not set to an instance of an object. ... at Microsoft.OData.Client.ClientEdmModel.<>c__DisplayClass19.<GetOrCreateEdmTypeInternal>b__d(IEdmSchemaElement et) ... at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable1 source, Func2 predicate) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmTypeInternal(IEdmStructuredType edmBaseType, Type type, PropertyInfo[] keyProperties, Boolean isEntity, Nullable1 hasProperties) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmType(Type type) ... at Microsoft.OData.Client.DataServiceContext.IsSingletonTypeTElement ... at Microsoft.OData.Client.DataServiceContext.Execute[TElement](Uri requestUri, String httpMethod, OperationParameter[] operationParameters) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_11.<Execute>b__1() ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_01.b__0() ...
06:48:57.05 Error Timestamp 02-Apr-2017 06:48:57 06:48:57.05 Error Machine SMC-WWW2 06:48:57.05 Error Useragent Mozilla/5.0 (compatible; AhrefsBot/5.2; +http://ahrefs.com/robot/) 06:48:57.05 Error Client 141.101.76.154 (141.101.76.154) 06:48:57.05 Error Referrer
06:49:07.64 Error Handle Section At Error occured at HandleSectionErrorAttribute handling - Error occured at Sdl.Web.Delivery.Service.AbstractODataService : HandleException and Handling (http://www.sharjah24.ae/ar/sharjah/172266-%D8%A7%D9%84%D9%85%D9%86%D8%B5%D9%88%D8%B1%D9%8A-%D9%86%D8%B3%D8%AA%D9%82%D9%8A-%D8%A7%D9%84%D8%AA%D8%B3%D8%A7%D9%85%D8%AD-%D9%85%D9%86-%D8%AA%D8%B9%D8%A7%D9%84%D9%8A%D9%85-%D8%AF%D9%8A%D9%86%D9%86%D8%A7-%D9%88%D9%85%D9%86%D9%87%D8%AC-%D9%82%D9%8A%D8%A7%D8%AF%D8%AA%D9%86%D8%A7 by 108.162.245.250) ... Sdl.Web.Delivery.Service.ServiceQueryException (Sdl.Web.Delivery.Service) ... Failed to execute query ... at Sdl.Web.Delivery.Service.AbstractODataService.HandleException(Exception e) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_01.<Execute>b__0() ... at Sdl.Web.Delivery.Service.Utils.PerformRetry[T](Func1 block, Int32 retryCount) ... at Sdl.Web.Delivery.Service.Utils.Retry[T](Func1 block, Int32 retryCount, Boolean locking) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.ExecuteComponentPresentationMetaDAOMethod(Int32 publicationId, String methodName, Object[] parameters) ... at Sdl.Web.Delivery.Dynamic.ComponentPresentationFactory.GetComponentPresentationWithHighestPriority(Int32 componentId) ... at Indivirtual.SHARJAH24.Common.TridionComponentPresentationProvider.GetContent(String uri, String templateUri) ... at DD4T.Factories.ComponentPresentationFactory.TryGetComponentPresentation(IComponentPresentation& cp, String componentUri, String templateUri) ... at DD4T.Factories.ComponentFactory.TryGetComponent(String componentUri, IComponent& component, String templateUri) ... at Indivirtual.DD4T.Mvc.Controllers.BasePageController.GetModelForPage(String PageId, PageType type) ... at Indivirtual.SHARJAH24.Controllers.PageController.Page(String pageId) ... at lambda_method(Closure , ControllerBase , Object[] ) ... at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) ... at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) ... at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult2.CallEndDelegate(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.b__3d() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.b__1c() ... at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.b__1e(IAsyncResult asyncResult) ... System.NullReferenceException (Microsoft.OData.Client) ... Object reference not set to an instance of an object. ... at Microsoft.OData.Client.ClientEdmModel.<>c__DisplayClass19.b__d(IEdmSchemaElement et) ... at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable1 source, Func2 predicate) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmTypeInternal(IEdmStructuredType edmBaseType, Type type, PropertyInfo[] keyProperties, Boolean isEntity, Nullable1 hasProperties) ... at Microsoft.OData.Client.ClientEdmModel.GetOrCreateEdmType(Type type) ... at Microsoft.OData.Client.DataServiceContext.IsSingletonType[TElement]() ... at Microsoft.OData.Client.DataServiceContext.Execute[TElement](Uri requestUri, String httpMethod, OperationParameter[] operationParameters) ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_11.b__1() ... at Sdl.Web.Delivery.Service.ODataV4Service.<>c__DisplayClass15_0`1.b__0() ...

Anyone based this issue, Any help would be highly appreciated.

Answer 1

CPU High issue was gone after upgrading to microservices.

Internal server Error fixed by upgraded all the DD4T packages to the latest release and it includes NewtonSoft.JSON 10.0.1 (the latest version)

Answer 2

It seems like you have a missing value/content somewhere in your index page(s), perhaps a certain type of Component Presentation or a some other attribute.

It looks like the problem lies within the MainArticles Model Extension:

http://www.sharjah24.ae/ar/ 
 System.ArgumentNullException (System.Core) ... Value cannot be null. ... Parameter name: source
at Indivirtual.SHARJAH24.Model.ModelExtension.MainArticles(IPage page, Int32 mainArticleCount, Boolean populateAuthors)

Perhaps the query returns an empty result and your model extension isn't checking for null, i.e. there is a list it's trying to traverse while looking for an Index Model, but it can't find the index page that maps to the model, or it can't build the model due to some other missing parameter:

System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable1 source,
  Func2 predicate) ... at Indivirtual.SHARJAH24.Model.ModelExtension.MainArticles(IPage page, Int32 mainArticleCount, Boolean populateAuthors) ... at Indivirtual.SHARJAH24.Controllers.PageController.GetIndexModel(IPage page) ... at 

I would look closely at this index page: http://www.sharjah24.ae/ar/ and see if there is a missing component or metadata parameter or something that isn't to your index page content creation standard.

I would also add some null checks into your ModelExtension.MainArticles and throw a custom exception with a clear error message, so that when this scenario occurs again, you know quickly where to go to fix the content issue.