The subprocess-booting test suites hand-picked fixed ports in a cramped ~3955-4021 range, and
156-schedule-read-path deviated to a RANDOM port (3900 + rand%90) that overlapped those fixed
ports. Under CI load two servers could race on the same port, surfacing as flaky "no such table:
devices" / "FOREIGN KEY constraint failed" (a server answering a request against a half-migrated
or wrong DB). It's environmental — the suites pass locally and in isolation.
Fix: a shared test/helpers/free-port.js (bind :0 on loopback, read the OS-assigned port, release)
called in before() so every suite gets a guaranteed-unique ephemeral port — concurrent suites can
no longer collide, and no one has to hand-assign ports.
- Codemod converted 30 suites: const PORT = <fixed|random> -> let PORT (+ BASE) assigned via
`PORT = await freePort()` at the top of before().
- 3 hand-fixed (different structure): 148-eviction-storm (lowercase `base`), boot-health (no
before() — allocates PORT + a throwaway SEED_PORT inside the test, replacing the hardcoded
3894), totp-keyrotation (no before() — allocates at the test start before bootServer()).
No fixed 39xx/40xx ports remain. Full server suite 435/435; the 4 hand-touched suites pass in
isolation. Pure test-infra change — no app code touched.
Field-safe SERVER net. A device opening duplicate/rapid sockets (the APK duplicate-socket bug,
separate track) currently churns through evictions during the reconnect-throttle's 30s
post-restart WARM-UP (only the hard ceiling 20 applies then, so an 8-in-9s burst passes
undamped and each new socket evicts the prior). This makes the server absorb it: a thrashing
PAIRED device converges to ONE stable connection and stays online.
- lib/session-settle.js (decision only; bounded, swept): shouldHold(deviceId, incumbentAlive)
— true only when a socket was accepted for this device within SESSION_SETTLE_WINDOW_MS
(config, default 2500ms) AND the incumbent is alive. Warm-up-independent.
- deviceSocket register gate (just before evictPriorSocket): if a LIVE incumbent exists and
we're inside the window, SOFT-REFUSE the new socket (device:throttled reason=session_settle
+ disconnect) and keep the incumbent; else accept + evict + (re)arm the window.
- LIVENESS SAFEGUARD (load-bearing): only hold when the incumbent socket is actually in the
/device namespace — a dead/half-open incumbent is replaced, NEVER stranding the device (max
hold is the 2.5s window from the incumbent's accept, then any new socket is accepted).
- Soft refusal, NEVER a quarantine (reuses patch1's paired-safe philosophy); single-session
enforcement intact for a legitimate move; unpaired/abusive flapping still caught by the
existing limiters. O(1), no loop impact.
Tests (liveness first-class): live incumbent holds + DEAD incumbent replaced (not stranded);
storm of 6 sockets converges to ONE, stays online, not quarantined (during warm-up); single-
session move past the window replaces cleanly; unit decision + bounded sweep. The
evicted-socket-rearm test shrinks its settle window so it still exercises the eviction path.
Suite 336/336.
