test: write scheduler barrier files atomically - #2069
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Path.write_text is open-then-write: it creates and truncates the file first and the content lands afterwards. The parallel harness contract polls for `<suite>.ready` to appear and then parses its content as the leader pid, so a reader that wins that window sees an empty file and fails with `ValueError: invalid literal for int() with base 10: ''` -- a spurious FAIL of the harness contract with a scheduler-side cause. The same shape applied to `<suite>.leader-exited`. Publish the barrier files through a helper that writes a same-directory temp file and os.replace()s it onto the destination, which is atomic on POSIX and Windows: a poller now sees either no file or complete content. All three barrier publications go through it. Pin the contract structurally (no timing): the scheduler may not write a barrier file in place, and it must rename into place instead. The pin is RED on the previous scheduler. Distilled from #1188 with co-author credit. Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com> Co-authored-by: Kody <kaidi.shi.1121@gmail.com> Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>
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What
scripts/run-test-wave.pypublishes its test-barrier files (<suite>.ready,<suite>.leader-exited) through a newpublish_barrier_file()helper: write a same-directory temp file, thenos.replace()it onto the destination. All three barrier writes go through it.tests/test_parallel_harness_contract.shgains a structural pin: the scheduler may not write a barrier file in place withPath.write_text, and it must rename into place. No timing, no sleeps.Why
Path.write_textis open-then-write: it creates and truncates the file first and the content lands afterwards. The harness contract polls for<suite>.readyto appear and then parses its content as the leader pid (int(ready.read_text())), so a reader that wins that window sees an empty file and fails withValueError: invalid literal for int() with base 10: ''— a spurious FAIL of the harness contract with a scheduler-side cause (an O9 flake, fixed in production, not in the test).os.replaceis atomic on POSIX and Windows, so a poller now sees either no file or complete content.Distilled from #1188 with co-author credit to @Geek0x0 — the fix was buried in that feature PR (commit
f1aea59600, "fix(ci): make test-barrier writes atomic"); this PR lands only that fix and leaves the rest of #1188 untouched.Verification
bash tests/test_parallel_harness_contract.shwithorigin/main's scheduler swapped in → rc=1,FAIL: scheduler barrier files are written in place (non-atomic); with this branch →Parallel harness contract passed(every case unchanged, includingtimeout_exit_race, which exercises the barrier path end to end).python3 -m py_compile scripts/run-test-wave.pyOK; the helper exercised directly: exact content, overwrite works, no temp-file residue.bash scripts/check-no-test-skips.shOK.shellcheck -s bashon the contract: 0 findings before and after.