test(iouring): regression arms for #712 (fixed by #793) - #767
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…tion must see the close (celeris#712) Measure-first: a sync-mode HTTP/1 connection whose header timer or ReadTimeout closes it on a paused worker, which parks in that iteration. Controls: the same close on a worker that keeps its listener, and on an AsyncHandlers engine.
…sweep caps the ring wait (celeris#712) A paused worker with no drain waits up to 1 s per iteration and runs checkTimeouts every 32nd, so the ReadTimeout close came past the arm's 10 s bound (measured: never within 13 s, 10/10). With a transplant set, as on the adaptive standby, the sweep caps the wait.
…ks (celeris#712) On a DEFER_TASKRUN ring a cancelled recv completes as task work, which runs only inside an io_uring_enter with GETEVENTS, and until then the recv keeps its reference to the file. finishClose's HTTP/1 fast path is a plain close(fd), so a sync-mode connection closed in the iteration that parks a paused worker kept its socket ESTABLISHED, and its client got no FIN, until something woke the worker: the pre-park submit (celeris#657 A5) was an enter without GETEVENTS, and the park waits on a Go channel. The pre-park enter is now Ring.SubmitAndFlush, io_uring_enter(fd, pending, 0, GETEVENTS): it submits what is queued and runs the deferred work without waiting, and it is made even when nothing is left to submit. One syscall per park; parks are rare.
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. 📝 WalkthroughWalkthroughAdds Linux-only io_uring regression tests for FIN delivery when synchronous HTTP/1 connections close as workers park. The tests cover timeout-triggered closes, running and async controls, and batches of 64 connections. No production implementation changes are included. Changesio_uring FIN Close Tests
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~20 minutes Change: Other · Severity of issue fixed: Medium Merge Risk: 🔵 Low · up to The new tests can fail before reaching the parked-worker scenario or pass without confirming FIN delivery. Correct both test conditions before relying on them as a regression guard. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Codecov Report✅ All modified and coverable lines are covered by tests. 📢 Thoughts on this report? Let us know! |
…ried At CI's 8 MiB memlock the kernel gives a closed ring's pages back 12-23 ms after the close, and startFDLEngine does not wait that out: an engine started right after another ring closed failed with ENOMEM (measured on the celeris#713 branch, 3 of 10 runs per shape right after a fixture ring), and its cleanup then waited 5 s on a Listen result it had already consumed. The tests now start through startRingRetried662, as the other back-to-back engine tests do.
… whether the rings defer their task work (celeris#712) One io_uring_enter runs at most IO_LOCAL_TW_DEFAULT_MAX (20) deferred completions per local-work pass on kernel 6.13 and later, and an enter with min_complete 0 makes at most two such passes. The single-connection arms cannot see that limit. The two new arms close 64 mid-header connections on a paused worker together, by one checkTimeouts pass (ReadTimeout, on a draining worker) or by their header timers, and require every client to see its close while the worker stays parked. The arms now log defer_taskrun as well as the tier: a COOP_TASKRUN ring logs tier=high too, and the defect needs a DEFER_TASKRUN ring. Under CELERIS_REQUIRE_IOURING_WORKERS=1 a ring without it fails the premise.
… ops are in flight (celeris#712) Round 1 made one io_uring_enter with GETEVENTS before the park, to run the deferred completion of the recv each connection closed in the parking iteration still had armed: until that completion runs, the recv holds its reference to the file, and the fast-path close(fd) sends no FIN. One enter runs at most IO_LOCAL_TW_DEFAULT_MAX (20) deferred completions per local-work pass on kernel 6.13 and later, and 64 connections closed by one checkTimeouts pass got 20 FINs. pendingRelease already holds each closed connState until its kernelInflight reports every op's terminal CQE. So the park now drains it first, with a fresh clock for its wall-clock backstop, and goes round again while an entry is left: the ring wait runs the deferred work and returns with the CQEs, as it does on a running worker, however many there are. An op the kernel never completes holds the park back by pendingReleaseHoldNanos (5 s) and one ring wait at most. The pre-park flush and Ring.SubmitAndFlush are gone; the A5 submit is main's again.
This was referenced Sep 28, 2026
Follow-ups from #767: a named CI interlock for the #712 tests, and the bare-metal failing-first
#795
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…rk change, which #793 superseded On main after #793 (3e7abba) the six park-FIN tests pass 18/18 without this branch's worker.go block, and the four park arms fail on main before #793 (1fdfcd4). #793 keeps the descriptor while a recv is owed and does not park while closeFDOwed is non-zero, so the park change is dropped and the tests stay as the regression guard.
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September 28, 2026 12:18
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Inline comments:
Review comments at @engine/iouring/park_close_fin_test.go:
- Around line 299-302: Increase the connection deadlines in the 64-connection
test at engine/iouring/park_close_fin_test.go lines 299–302 to cover all
sequential dials, writes, and reads, and adjust its close-observation bound.
Increase the single-connection deadline at engine/iouring/park_close_fin_test.go
lines 173–176 to allow acceptance and pause setup, and adjust that test’s
close-observation bound. Ensure both tests avoid timing knife-edges and reliance
on goroutine scheduling order.
- Around line 102-153: Update clientSeesClose to count only io.EOF as successful
peer closure; keep polling on timeouts and return failure for other read errors,
including connection resets. Ensure the single- and batch-case assertions
therefore accept only EOF as FIN delivery.
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Summary
This PR only adds tests. It adds the regression tests for celeris#712, whose fix is already on main.
The bug: on a DEFER_TASKRUN ring, a sync-mode HTTP/1 connection closed in the same iteration that parks a paused io_uring worker got no FIN until the worker woke up.
finishClose's plainclose(fd)releases nothing while the connection's armed recv still holds the file. That recv's cancelled completion is task work, and task work runs only inside anio_uring_enterwithGETEVENTS. A parked worker makes no such call. Both ends stayed ESTABLISHED.#793 (celeris#685,
3e7abba) fixed it. When a close path still owes the kernel an op on the descriptor, it now leaves the descriptor to itspendingReleaseentry. That entry closes the descriptor when the op's terminal CQE arrives. The worker does not park while such a close is outstanding (closeFDOwed), so the loop's ring waits run the deferred completions before the park, however many there are.This PR used to carry its own park change in
engine/iouring/worker.go. That change is dropped. The six #712 tests inengine/iouring/park_close_fin_test.gostay as the regression guard, and the file's header comment now names the fix on main. The PR's diff against main is that one test file.Fixes #712 (the fix is on main; this PR adds its regression guard).
Measured
Each run is the six tests with count 3, so 18 verdicts per tree. There are four park arms and two controls: a running worker, and an
AsyncHandlersengine, whose close shuts the socket down. The rings run with one io_uring worker, and every line readstier=high defer_taskrun=true.1fdfcd4) plus these tests3e7abba) plus these tests, without the oldworker.gochangeab1e9f2(current main23da5b5plus these tests)01/01), and the close came 0 ms after aResumeAccept.fin_seen_while_parked=0/64, and the header-timer arm read63/64. In both, all 64 closes arrived after a wake.05/08).64/64, withseen_after_wake=0.go test -race -count=3 -vin Docker linux/arm64 on kernel 7.0.12-linuxkit, at CI's 8 MiB memlock, withCELERIS_REQUIRE_IOURING_WORKERS=1.go build,go vetandgo test -cof./engine/iouring/all exit 0 for linux/amd64 and linux/arm64.CI coverage
Unit's
engine/iouringstep runs the whole package with-v. It fails on any--- SKIPline other than the five that other steps enforce, so these six tests run there and cannot skip quietly.A named interlock (a pass count for these six tests by name) is still open as item 1 of #795.