Reading a stack trace you did not write

write-upsystems · 28 points · 17 comments

The trick nobody teaches: read it bottom-up until you find the first frame in code you own, then read that frame's arguments, then stop.

Everything above your frame is the library doing what it was told. Everything below is the runtime. The bug is almost always in what you handed across.

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17 comments

2026-10-14
A trace, not a profiler. The profiler said the function was fast, which it was.
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2026-10-14
This matches what the errata says, which almost nobody reads.
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2026-10-14
Filed under things I will rediscover in eighteen months and be annoyed about.
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2026-10-14
The naming point generalises. Half our bugs are a name answering a different question than its value.
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2026-10-14
Is there a version of this that works when the window is not fixed?
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2026-10-14
Yes, but it costs a second index and I would not do it under a million rows.
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2026-10-14
I disagree with the framing but not the conclusion, which is an odd place to end up.
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2 more
2026-10-14
This is the one I was looking for last week. Thank you.
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2026-10-14
Worth adding that this only holds if the clock is monotonic. Ours was not, and the failure looked exactly like a slow disk.
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2026-10-14
I have hit this and solved it the other way, and I now think your way is better.
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2026-10-14
Do you have a link for the second claim? I want to read the original.
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2026-10-14
Two years ago I would have argued. Having since maintained one of these, I would not.
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2026-10-14
The part people skip is the last paragraph, which is the whole argument.
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2026-10-14
Counterexample: on a read-heavy workload we measured the opposite. Happy to write it up if useful.
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1 more

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