dotnet/aspnetcore

Misleading TaskCanceledException

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#4,747 opened on May 30, 2018

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 (7 comments) (0 reactions) (0 assignees)C# (37,933 stars) (10,653 forks)batch import
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Description

I have a WebApi endpoint that parses out the Request.Body itself rather than using Model binding due to performance reasons.

During some requests, I was getting a TaskCanceledException from a TextReader that I never gave any CancellationTokens too. After investigation, I found out that any read operations on the Request.Body after the Request was aborted will throw TaskCanceledExceptions. The stack trace at the time didn't list any Kestrel level code so I spent a lot of time trying to find out how a Stream can possibly cancel a token I never gave it.

This is a bit misleading and should probably change I think.

Contributor guide

Tech stack
csharp
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
understand ASP.NET Core request pipelineknow CancellationToken basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the source of the TaskCanceledException in the HttpRequest body stream, likely in the Kestrel server implementation. Look at the RequestBodyStream or similar classes in the dotnet/aspnetcore repository. The issue discussion (https://github.com/dotnet/aspnetcore/issues/4747) contains insights. Consider if the exception should be changed to a more specific one like OperationCanceledException, and whether the cancellation token is exposed appropriately.
Misleading TaskCanceledException · dotnet/aspnetcore#4747 | Good First Issue