B <> O upload timeouts

[yondonfu]

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At the moment, we use a single HTTP timeout for B <> O segment submission. The timer for this timeout starts when B submits a request to /segment and ends when B finishes reading the response body returned by O.

This timeout covers:

• Segment upload time to O
• Transcode time on O
• Response time on O [1]

[1] Note rendition download time is not included here since the response from O to segment submission includes the URLs for the renditions which are downloaded separately.

If there are networking/bandwidth issues with O causing slow uploads, B could end up waiting the full HTTP timeout (defaults to 4x the segment duration) before it fails over to a different O. There is an opportunity to detect the networking/bandwidth issue with O earlier if B defined more granular timeouts in addition to the HTTP timeout for segment submission.

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B can define an upload timeout which is strictly shorter than the segment submission HTTP timeout. The upload starts when B submits a request to /segment and ends when B receives a response status from O [2]. If this upload exceeds the defined timeout, then B can fail over to a different O instead of waiting the full segment submission HTTP timeout. The upload timeout might be defined as segment duration * uploadTimeoutMultiplier where uploadTimeoutMultiplier could default to something like 0.5 such that a 2 second segment has a 1 second upload timeout.

Code sketch

[2] The transcoding protocol has O send back a response status to acknowledge that the upload completed before it starts sending back data in the response body which only begins when it completes transcoding.