[Flight] Include I/O not awaited in user space #33715
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eps1lon
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| } | ||
| case PROMISE_NODE: { | ||
| if (node.end <= request.timeOrigin) { | ||
| // This was already resolved when we started this render. It must have been either something | ||
| // that's part of a start up sequence or externally cached data. We exclude that information. | ||
| // The technique for debugging the effects of uncached data on the render is to simply uncache it. | ||
| return null; | ||
| return previousIONode; |
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The comment above makes we wonder whether this change may affect cached I/O. At least in the Flight fixture it doesn't seem to cause an issue with the cached third-party stream though.
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The previousIONode has its own check if it finished before this sequence so it’ll also be null.
We don’t really expect the future node to have finished before the previous. But for consistency I return it here.
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If I/O is not awaited in user space in a "previous" path we used to just drop it on the floor. There's a few strategies we could apply here. My first commit just emits it without an await but that would mean we don't have an await stack when there's no I/O in a follow up.
I went with a strategy where the "previous" I/O is used only if the "next" didn't have I/O. This may still drop I/O on the floor if there's two back to back within internals for example. It would only log the first one even though the outer await may have started earlier.
It may also log deeper in the "next" path if that had user space stacks and then the outer await will appear as if it awaited after.
So it's not perfect.