HttpClient - provide timeout per read/write operation in async methods

[karelz]

Users need timeout per read/write operation in async operations when using HttpClient -- i.e. on HttpContent:
Read/write operations can achieve it via CancellationTokens, however CopyToAsync has timeout only for the overall operation, not for individual read/write operations.

Note: Stream.ReadTimeout and Stream.WriteTimeout intentionally don't apply to async operations. Changing that would be a breaking change.

Repro: #36822 (comment)
Background and lengthy discussion in #74568

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Issue Details

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Users need timeout per read/write operation in async operations when using HttpClient -- i.e. on HttpContent:
Read/write operations can achieve it via CancellationTokens, however CopyToAsync has timeout only for the overall operation, not for individual read/write operations.

Note: Stream.ReadTimeout and Stream.WriteTimeout intentionally don't apply to async operations. Changing that would be a breaking change.

Background and lengthy discussion in #74568

Author:	karelz
Assignees:	-
Labels:	api-needs-work, area-System.Net.Http
Milestone:	Future

[stephentoub]

We could certainly add an API for this if we wanted to. Just noting this would be about usability more than anything else, since it's already possible to achieve the desired semantics with the existing APIs.
#74568 (comment)

[iSazonov]

this would be about usability more than anything else

If we consider only HttpClient, then yes, I agree, since HttpClient itself is designed for convenience.
But there's another side to it that we haven't discussed. I see that classes derived from Stream are widely used in various web APIs. This means that such streams can also hang in case of unexpected network or service loss. If this is indeed a problem, perhaps it should be discussed in a separate issue.

[stephentoub]

But there's another side to it that we haven't discussed. I see that classes derived from Stream are widely used in various web APIs.

We have discussed. They're cancelable. That's what the token is for.