IIS crashes on cancellation

[John Ligtenberg]

Hello,

When I call the cancel method in a static class in an ASP.NET site in which Abot runs, IIS crashes.

The relevant code:

private static CancellationTokenSource _cancellationTokenSource;

In the method which call Abot:

_cancellationTokenSource = new CancellationTokenSource();

 var result = await crawler.CrawlAsync(new Uri(startPage), _cancellationTokenSource);

A method in the static class initiates cancelling:

public static string Cancel()

{

try

{

if (_cancellationTokenSource == null)

{

return _message += "<br>_cancellationTokenSource was null<br><br>";

}

Task.Run(() => _cancellationTokenSource.Cancel());

_isRunning = false;

return _message += "<br>Cancelled error checking<br><br>";

}

catch (Exception ex)

{

_logger.Log(Level.Error, ex.Message, ex);

return _message += "<br><br>Error cancelling crawl<br><br>";

}

}

What can I do to prevent IIS crashing?

Yours,

John Ligtenberg

[sjdi...@gmail.com]

Can you give more information about the crash? Is there a specific exception thrown? What do the logs say?

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[John Ligtenberg]

First:

System.OperationCanceledException

   bij System.Threading.CancellationToken.ThrowOperationCanceledException()

   bij Abot2.Crawler.WebCrawler.ThrowIfCancellationRequested()

   bij Abot2.Crawler.WebCrawler+<ProcessPage>d__65.MoveNext()

   bij System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   bij System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(System.Threading.Tasks.Task)

   bij System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(System.Threading.Tasks.Task)

   bij Abot2.Crawler.WebCrawler+<<CrawlSite>b__64_0>d.MoveNext()

   bij System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   bij System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)

   bij System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)

   bij System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()

   bij System.Threading.ThreadPoolWorkQueue.Dispatch()

And subsequently:

Faulting application name: w3wp.exe, version: 10.0.19041.1, time stamp: 0x58c67bf3

Faulting module name: KERNELBASE.dll, version: 10.0.19041.662, time stamp: 0xec58f015

Exception code: 0xe0434352

Fault offset: 0x000000000002d759

Faulting process id: 0x2f1c

Faulting application start time: 0x01d7043a77121450

Faulting application path: c:\windows\system32\inetsrv\w3wp.exe

Faulting module path: C:\WINDOWS\System32\KERNELBASE.dll

Report Id: ea3a6c94-e682-45ce-a40d-40a0c4e36cb2

Faulting package full name: 

Faulting package-relative application ID: 

[John Ligtenberg]

Is there any other way to stop the crawling process ?

[sjdi...@gmail.com]

Anyone that cancels a task using a cancellationtoken (nothing to do with Abot/Abotx) will have to catch the cancellation exceptions that are thrown. Again, this has nothing to do with Abot, the cancellation token hook is just so Abot can play nicely in a larger cancellation process. You can stop Abot independently by setting the args.CrawlContext.IsCrawlStop or args.CrawlContext.IsHardStopRequested properties to true. The CrawlContext object is available in every event. You can see the difference between the two properties by reading the comments for each.

        private static void PageCrawlCompleted(object sender, PageCrawlCompletedArgs e)
        {
            e.CrawlContext.IsHardStopRequested = true;
        }

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