fix(previews): ffprobe hangs#60916
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Signed-off-by: Andrey Dyakov <adduxa@gmail.com>
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solracsf
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| } | ||
| foreach ($read as $pipe) { | ||
| $chunk = fread($pipe, 8192); | ||
| if ($chunk === false) continue; |
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| !feof($test_hdr_pipes[2]) ? $test_hdr_pipes[2] : null, | ||
| ]); | ||
| $write = $except = []; | ||
| if (stream_select($read, $write, $except, 5) === false) { |
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This 5 is a per-iteration timeout. Only the false (error) return is handled; the 0 (timeout) return falls through, $read becomes empty, the foreach does nothing, and the while loops again. So if ffprobe truly hangs (produces no output and never closes its pipes), this spins every 5s forever: the same "hangs indefinitely" symptom the PR title targets, just via a different path.
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Thanks! I will search for the solution.
Do you know if stdout is always <64k here? Is it acceptable to just read stderr first in this case?
This approach is used at https://github.com/adduxa/server/blob/1bcc80b5f45a0d8619df64edbd2fec797fd70cd9/lib/private/Preview/Movie.php#L374 for ffmpeg
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Summary
Fix pipe buffer deadlock in
useHdr()inlib/private/Preview/Movie.php.When
ffprobeproduces more than ~64KB on stderr, the sequentialstream_get_contentscallsdeadlock: PHP blocks reading stdout while ffprobe blocks flushing stderr. This caused
occ preview:generate-allto hang indefinitely on certain video files.A tempting workaround is to swap the two
stream_get_contentscalls (reading stderr first),but I'm not sure if ffprobe is guaranteed to produce <64KB on the stdout for this call.
Fix drains both pipes concurrently using
stream_selectwith non-blocking I/O.TODO
Checklist
3. to review, feature component)stable32)AI (if applicable)