gh-154194: Degrade frames in Tachyon instead of failing the sample#154195
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maurycy wants to merge 3 commits into
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gh-154194: Degrade frames in Tachyon instead of failing the sample#154195maurycy wants to merge 3 commits into
maurycy wants to merge 3 commits into
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I believe that the CI failures are caused by the fact that |
pablogsal
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Jul 20, 2026
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I still need more time but some nits
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| Py_ssize_t len = GET_MEMBER(Py_ssize_t, unicode_obj, unwinder->debug_offsets.unicode_object.length); | ||
| if (len < 0 || len > max_len) { | ||
| if (len < 0 || len > MAX_REMOTE_READ) { |
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This rejects valid task names above 256 KiB instead of truncating them, so async sampling can still fail. We should cap read_len, not len, and test this boundary.
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As always, see #154194 for the context. Shortly: right now remote inspection fails the whole sample when it hits the limits (and we're really not sure what are the best limits) OR always when reading a part fails. This is too strict, wasteful and introduces scary bias, as observed in https://discuss.python.org/t/tachyon-97-error-rate/107619.
The PR introduces graceful degradation with the sentinels like
<unreadable frame>(funcname),<unknown function>(funcname),<unknown file>(filename) and the(len=N)suffix if we hit the cap. Also, it introducesMAX_REMOTE_READas a safety check, and attemps to better differentiate between transient failures in_Py_RemoteDebug_IsFatalReadError().Importantly: degraded frames are never cached, while the truncated strigs are cached.
Fixes #154194
_remote_debugging: Degrade gracefully reads instead of failing the whole read completely #154194