Deliver outbound stream errors to channels. #315
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Motivation: When we hit a stream error on an outbound frame, we don't currently distinguish between them and channel errors. This makes it impossible for anyone to tell them apart. It also makes it impossible for the multiplexer to deliver these errors into the relevant stream channels that triggered them, making it essentially certain they'll be lost. Better diagnostics would be good, so we are providing them. Modifications: - Add new StreamError type that carries a stream ID and an underlying error. - Emit this StreamError type for outbound stream errors. - Deliver this StreamError type into the relevant child channels when possible. Result: Better diagnostics for stream errors.
| if let streamError = error as? NIOHTTP2Errors.StreamError, | ||
| let channel = self.streams[streamError.streamID] { | ||
| channel.receiveStreamError(streamError) | ||
| } |
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Is it possible to receive a stream error for a stream we don't know about? Wondering whether we should drop stream errors for streams we aren't aware of (to avoid downstream handlers, for example, closing the channel on receiving an error).
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Yes, it is, but I don't think we should drop them. Just because the multiplexer doesn't know about them doesn't mean the error is not of interest.
| channel.receiveStreamError(streamError) | ||
| } | ||
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| context.fireErrorCaught(error) |
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Do we really want to unconditionaly forward it to the next channel handler even if we deliver it to one of our child channels?
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Yeah, I think we probably do: this ensures that errors don't suddenly go missing when they were reported before.
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Even though, to late to the game... 👍 Great change, thanks! |
Motivation:
When we hit a stream error on an outbound frame, we don't currently
distinguish between them and channel errors. This makes it impossible
for anyone to tell them apart. It also makes it impossible for the
multiplexer to deliver these errors into the relevant stream channels
that triggered them, making it essentially certain they'll be lost.
Better diagnostics would be good, so we are providing them.
Modifications:
error.
possible.
Result:
Better diagnostics for stream errors.