A task was canceled - what does this mean? - asynchronous

Question

I'm using the Azure Search .Net SDK.
I'm calling a synchronous (NOT ASYNC) function like this:
var searchResults = searchIndexClient.Documents.Search<T>(searchText, searchParameters);
It usually works. I'm not using any async functions, but somehow the error I just got looks like an async error:
System.Threading.Tasks.TaskCanceledException: A task was canceled.
CancellationToken: IsCanceleationRequested=false
Task: Id = 556, Status = Canceled, Method = "{null}", Result = "{Not yet computed}"
StackTrace:
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1.ConfiguredTaskAwaiter.GetResult()
at Microsoft.Azure.Search.DocumentsOperations.<DoContinueSearchWithHttpMessagesAsync>d__153.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.Runtime.CompilerServices.ConfiguredTaskAwaitable1.ConfiguredTaskAwaiter.GetResult()
at Microsoft.Azure.Search.DocumentsOperationsExtensions.<SearchAsync>d__151.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.Runtime.CompilerServices.TaskAwaiter1.GetResult()
at Microsoft.Azure.Search.DocumentsOperationsExtensions.Search[T](IDocumentsOperations operations, String searchText, SearchParameters searchParameters, SearchRequestOptions searchRequestOptions)
at MyApp.AzureSearch.AzureSearchService.PerformSearch[T](String searchText, SearchParameters searchParameters) in c:\Projects\MyAppServer\src\MyApp.AzureSearch\AzureSearchService.cs:line 359
at MyApp.AzureSearch.AzureSearchService.Search[T](String searchText, List1 searchFields, SearchMode searchMode, List1 select, Nullable1 skip, Nullable1 top, String filter, Boolean includeTotalResultCount, List1 orderBy) in c:\Projects\MyAppServer\src\MyApp.AzureSearch\AzureSearchService.cs:line 262
at MyApp.AzureSearch.AzureSearchService.SearchEmails(Guid userId, String origin, String searchText, Nullable1 skip, Nullable1 top, Boolean includeTotalResultCount, Boolean includeHtmlBody, Boolean orderByProcessedAscending, String interactionStatus) in c:\Projects\MyAppServer\src\MyApp.AzureSearch\AzureSearchService.cs:line 167
at MyApp.Domain.MyAppMessages.Command.MyAppMessagesAllNoticedUpdater.Handle(VisitorSession userSession, NoticeAllMyAppMessages processCommand) in c:\Projects\MyAppServer\src\MyApp.Domain\MyAppMessages\Command\MyAppMessagesAllNoticedUpdater.cs:line 30

Answer 1

Most likely, the client timeout expired before the search has completed. Are you seeing this error when you submit a particularly complex query? If needed, you can look at the search performance in your service using search traffic analytics.
The reason you're seeing an "asynchronous" exception is that the synchronous version of the API is just a wrapper over asynchronous primitives.

Answer 2

Pass CancellationToken=null and make the code as async methods.