A stalled server no longer reads as "your clock is ahead" #251

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jared merged 3 commits from clock-skew-lag into lotus 2026-09-28 22:40:14 -04:00

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3 Commits

Author	SHA1	Message	Date
Lotus CI	f0865115a4	Merge remote-tracking branch 'origin/lotus' into clock-skew-lag	2026-09-28 22:11:31 -04:00
Lotus CIandClaude Opus 5.5	3e5fdd0dab	test(e2e): clock-ahead warning needs a minute of samples (#158) ... "Ahead" is now reported only once it has held for a minute of fresh samples (a stalled server delivers late and reads as ahead). The test sends its ticks, checks nothing is shown yet, fast-forwards the page clock past a minute and sends two more. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA	2026-09-28 22:08:13 -04:00
Lotus CIandClaude Opus 5.5	bb569d69a2	fix: a stalled server no longer reads as "your clock is ahead" ... Incident 2026-09-29: the homeserver's host ran out of memory and stalled for ~2 minutes. The /sync that finally went out carried events whose `age` was computed ~30 s before it arrived, so every client showed "Your computer's clock is 30 seconds ahead of the server" while the real problem was the server (all host clocks were within 0.25 s the whole evening). The skew estimate was the median of the last 5 samples, and a sample is local skew + delivery delay, so one late /sync with a handful of events tripped it. - Estimate = the LOWEST sample of the last 5 minutes: delay only ever adds, so the fastest-delivered event is the truest. - "Behind" (which a delay can't cause) is reported as soon as there are 3 samples, like before. "Ahead" must hold across samples received at least a minute apart, so a single late burst never trips it. - Samples are aged on the monotonic clock, and a change of the local clock (someone fixing it) resets the measurement, so the warning clears at once. - Only events stamped by our own homeserver are sampled: a federated event's origin_server_ts is the other server's clock. - Wording: "This device's clock is … Voice calls and encrypted messages can fail until it's corrected." / call bar "Device clock … : calls may fail" (was "will fail"). Unit tests: the incident (late burst after normal traffic, and a fresh client whose first samples are all late), mixed slow/fast deliveries, ahead only after a minute, behind at once, hysteresis, clock fixed. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA	2026-09-28 21:40:02 -04:00