What is causing the "XConnect Exception Filter OnException()" errors in xconnect log files?

Question

I see errors like XConnect Exception Filter OnException(), url - "https://xconnect/refdata/definitiontype/ensure" in the xconnect log files. What is causing those errors and does it mean something is configured wrong?

These can be seen after opening the home page of the Storefront.

2019-05-23 09:49:31.586 +02:00 [Information] XConnect Test Host Application Start, Machine: "7CFA130A43F3", Site: "xconnect", AppId: "/LM/W3SVC/928776700/ROOT"
2019-05-23 09:49:32.930 +02:00 [Information] Certificate Validation Filter Enabled, Thumbprint: 3CB4DA6F75DC4A297D08FFBEDCFC4DBCC0167331
2019-05-23 09:49:32.931 +02:00 [Information] SSL Validation Filter Enabled
2019-05-23 09:49:33.998 +02:00 [Information] SystemPerformanceCounters Constructor, Instance:xconnect, Path: C:\inetpub\wwwroot\xconnect\App_Data\Diagnostics, CounterFilePattern: *.json
2019-05-23 09:51:35.299 +02:00 [Information] Create "XdbContextLoggingPlugin"
2019-05-23 09:51:35.313 +02:00 [Information] Register "XdbContextLoggingPlugin"
2019-05-23 09:51:35.442 +02:00 [Error] XConnect Exception Filter OnException(), url - "https://xconnect/odata/DeviceProfiles?%24filter=Id+eq+21a018ec-4504-42e7-bfc6-f0a2b368005a"
    System.OperationCanceledException: The operation was canceled.
       at System.Threading.CancellationToken.ThrowOperationCanceledException()
       at System.Net.Http.HttpContentExtensions.<ReadAsAsyncCore>d__0`1.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Web.Http.ModelBinding.FormatterParameterBinding.<ExecuteBindingAsyncCore>d__0.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Web.Http.Controllers.HttpActionBinding.<ExecuteBindingAsyncCore>d__0.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Web.Http.Controllers.AuthenticationFilterResult.<ExecuteAsync>d__0.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()
    2019-05-15 14:51:50.810 +02:00 [Error] XConnect Exception Filter OnException(), url - "https://xconnect/refdata/definitiontype/ensure"
    System.OperationCanceledException: The operation was canceled.
       at System.Threading.CancellationToken.ThrowOperationCanceledException()
       at System.Net.Http.HttpContentExtensions.<ReadAsAsyncCore>d__0`1.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---

Answer 1

I've contacted Sitecore Support and below is their response:

The mentioned above exception usually happens due to the fact that xConnect has not responded within 5 seconds. So I believe it happened due to xConnect has been restarting and its nothing to worry about.

In case the exception occurs not only once after xConnect start please check whether app pool user has required access rights.. For example, please refer to the following article: https://blog.wenstor.com/2015/05/cess-to-registry-key-global-is-denied-in-sitecore.html Could you please check if providing access to the app pool user fixes the errors?