fix(api): log ffmpeg stderr when a streamed render fails - #297
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Streamed ffmpeg renders (mixdown export, region trims, stem MP3, video mux) sent stderr to DEVNULL. When ffmpeg died mid-stream the client received a truncated file with HTTP 200 already committed -- and no trace of the failure existed anywhere, making "my export is broken" reports unsolvable. stderr is now drained into a bounded tail (mandatory anyway once it is a pipe -- an undrained full pipe would deadlock ffmpeg) and logged at WARNING with a per-endpoint context (job id, format, stems) when the process exits non-zero. Kills we initiated on client disconnect are expected and stay silent; EOF-then-nonzero is the failure signature, since returncode stays None until wait() even for an exited child. Closes #280
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Closes #280. Phase 1 of #272 — plan: #272 (comment) (PR-1D).
What
_stream_ffmpeg(mixdown export, stem region trims, stem MP3 region, video mux) sent stderr toDEVNULL. If ffmpeg died mid-stream, the user downloaded a truncated file under an already-committed HTTP 200 — and the failure left no trace anywhere.mixdown job=… ext=… stems=…) + the stderr tail.returncode(which staysNoneuntilwait()reaps the child even when it already exited — caught by the new test, fixed).Testing
_stream_ffmpegwith a Python stub subprocess: failure logs context + stderr tail while still delivering the partial stream; clean exit logs nothing. Cross-platform, no ffmpeg needed.ruff check+ruff format --checkclean.🤖 Generated with Claude Code