Restarting Azure app service fixes exception - azure-web-app-service

Question

I have an azure web app service running ASP.net project. Client side is JavaScript, server side is C#.
We have been seeing errors on JSON.Parse call on the response from a server failing with:
SyntaxError: Unexpected token S in JSON at position 0
at JSON.parse (<anonymous>)
The call is made to the /SubmitPromoCode on the controller. This is what I found on the eventLogs from the KUDU console:
<Event>
<System>
<Provider Name="ASP.NET 4.0.30319.0"/>
<EventID>1309</EventID>
<Level>2</Level>
<Task>0</Task>
<Keywords>Keywords</Keywords>
<TimeCreated SystemTime="2018-11-13T18:52:01Z"/>
<EventRecordID>494282343</EventRecordID>
<Channel>Application</Channel>
<Computer>RD0003FFF90BE8</Computer>
<Security/>
</System>
<EventData>
<Data>3005</Data>
<Data>An unhandled exception has occurred.</Data>
<Data>11/13/2018 6:52:01 PM</Data>
<Data>11/13/2018 6:52:01 PM</Data>
<Data>c16536d64f344a93880f7b7f906fbb37</Data>
<Data>19948</Data>
<Data>45</Data>
<Data>0</Data>
<Data>/LM/W3SVC/212763173/ROOT-1-131865099388319272</Data>
<Data>Full</Data>
<Data>/</Data>
<Data>D:\home\site\wwwroot\</Data>
<Data>RD0003FFF90BE8</Data>
<Data/>
<Data>1408</Data>
<Data>w3wp.exe</Data>
<Data>IIS APPPOOL\azurepassredemption__8726</Data>
<Data>HttpException</Data>
<Data>
The client disconnected. at System.Web.Hosting.IIS7WorkerRequest.BeginRead(Byte[] buffer, Int32 offset, Int32 count, AsyncCallback callback, Object state) at System.Web.HttpBufferlessInputStream.BeginRead(Byte[] buffer, Int32 offset, Int32 count, AsyncCallback callback, Object state) at System.IO.Stream.<>c.<BeginEndReadAsync>b__43_0(Stream stream, ReadWriteParameters args, AsyncCallback callback, Object state) at System.Threading.Tasks.TaskFactory`1.FromAsyncTrim[TInstance,TArgs](TInstance thisRef, TArgs args, Func`5 beginMethod, Func`3 endMethod) at System.IO.Stream.BeginEndReadAsync(Byte[] buffer, Int32 offset, Int32 count) at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken) at Microsoft.Owin.Host.SystemWeb.CallStreams.DelegatingStream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken) at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count) at System.IO.StreamReader.<ReadBufferAsync>d__97.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.IO.StreamReader.<ReadToEndAsyncInternal>d__62.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.OwinRequest.<ReadFormAsync>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.OpenIdConnect.OpenIdConnectAuthenticationHandler.<AuthenticateCoreAsync>d__1a.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationHandler.<BaseInitializeAsync>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware`1.<Invoke>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContextStage.<RunApp>d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware`1.<Invoke>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContextStage.<RunApp>d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.<DoFinalWork>d__2.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult ar) at System.Web.HttpApplication.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
</Data>
<Data>
https://www.xxxxxxxxxxxxxxxxxx.com:443/SubmitPromoCode/Submit
</Data>
<Data>/SubmitPromoCode/Submit</Data>
<Data>67.214.103.177</Data>
<Data>live.com#xxxxxxxxxxx#Outlook.com</Data>
<Data>True</Data>
<Data>OpenIdConnect</Data>
<Data>IIS APPPOOL\azurepassredemption__8726</Data>
<Data>27</Data>
<Data>IIS APPPOOL\azurepassredemption__8726</Data>
<Data>False</Data>
<Data>
at System.Web.Hosting.IIS7WorkerRequest.BeginRead(Byte[] buffer, Int32 offset, Int32 count, AsyncCallback callback, Object state) at System.Web.HttpBufferlessInputStream.BeginRead(Byte[] buffer, Int32 offset, Int32 count, AsyncCallback callback, Object state) at System.IO.Stream.<>c.<BeginEndReadAsync>b__43_0(Stream stream, ReadWriteParameters args, AsyncCallback callback, Object state) at System.Threading.Tasks.TaskFactory`1.FromAsyncTrim[TInstance,TArgs](TInstance thisRef, TArgs args, Func`5 beginMethod, Func`3 endMethod) at System.IO.Stream.BeginEndReadAsync(Byte[] buffer, Int32 offset, Int32 count) at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken) at Microsoft.Owin.Host.SystemWeb.CallStreams.DelegatingStream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken) at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count) at System.IO.StreamReader.<ReadBufferAsync>d__97.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.IO.StreamReader.<ReadToEndAsyncInternal>d__62.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.OwinRequest.<ReadFormAsync>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.OpenIdConnect.OpenIdConnectAuthenticationHandler.<AuthenticateCoreAsync>d__1a.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationHandler.<BaseInitializeAsync>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware`1.<Invoke>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContextStage.<RunApp>d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware`1.<Invoke>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.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContextStage.<RunApp>d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.<DoFinalWork>d__2.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult ar) at System.Web.HttpApplication.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
</Data>
</EventData>
</Event>
Does anyone know why this problem occurred and got fixed by just restarting the app service?

Answer 1

I get your problem when locally removed the MVC dependencies on my project and set the dependency to the DLLS built by that project. This allowed me to debug inside of MVC calls, which was extremely handy, but publishing the project in this state was the cause of this issue.
Rebuilding the project so the dependencies were set to the DLLs that come with the standard MVC install fixes the issue.