Support stream cancellation #142
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We now support stream cancellation via the `OutBodyIface` API's `outBodyCancel` function. Some care was taken to ensure that cancelling idle streams does not result in protocol errors. In particular, `outBodyCancel` will wait until either the headers have been sent successfully or an exception occurs. If we aren't totally sure that the headers are sent, we won't send `RST_STREAM`.
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@kazu-yamamoto Could you please request a review from @edsko on this as well? Thank you! |
edsko
reviewed
Aug 28, 2024
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This depends on kazu-yamamoto/http-semantics#11 . |
edsko
requested changes
Aug 28, 2024
The 'outputQ' invariant is what guarantees we won't send @RST_STREAM@ frames ahead of some still-enqueued data frames for a stream. Additionally, the previous commit was unnecessarily tracking whether headers had been sent on a stream to deal with a bug which we have now *actually* fixed, so we no longer track whether headers are sent per-stream as we were.
Track whether a stream is finished or cancelled in a `TVar` rather than an `IORef`, and update that `TVar` in a single transaction which also writes the appropriate http-semantics `StreamingChunk` to the queue.
edsko
requested changes
Aug 29, 2024
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This looks good to me now, and I think we could merge this now as-is, but I think we can make a two minor improvements (as well as remove that redundant constructor, mentioned above):
- I wonder what should happen with
outBodyPushetc once the stream is finished. This should be considered a user bug, I think, but it might be good to detect these cases and throw an exception. - Let's try and avoid the redundancy between the two
outBodyIfaceconstructions (all the more important after we also implement (1).
Network/HTTP2/H2/Types.hs
Outdated
| @@ -208,6 +214,7 @@ data HTTP2Error | |||
| | StreamErrorIsSent ErrorCode StreamId ReasonPhrase | |||
| | BadThingHappen E.SomeException | |||
| | GoAwayIsSent | |||
| | RSTStreamIsSent | |||
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Is this a leftover from a previous attempt? Doesn't seem to be used anywhere?
There was duplicated code in `Network.HTTP2.Client.Run` and `Network.HTTP2.Server.Worker` to construct a `OutBodyIface`. We have moved that to a dedicated module. We also now throw exceptions when a push or flush is attempted on a concluded stream.
edsko
reviewed
Aug 29, 2024
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LGTM! @kazu-yamamoto , this PR and kazu-yamamoto/http-semantics#11 and now ready for your review.
edsko
approved these changes
Aug 29, 2024
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I have released |
kazu-yamamoto
approved these changes
Aug 29, 2024
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A new version has been released. |
Merged
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We now support stream cancellation via the
OutBodyIfaceAPI'soutBodyCancelfunction. Some care was taken to ensure that cancelling idle streams does not result in protocol errors. In particular,outBodyCancelwill wait until either the headers have been sent successfully or an exception occurs. If we aren't totally sure that the headers are sent, we won't sendRST_STREAM.