Fix log timestamp UTC offset: broken on non-Linux, wrong for negative/half-hour DST everywhere - #4677
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On platforms other than Linux and Solaris, getTimeZone() read the timezone argument of gettimeofday(). That argument is obsolete: POSIX specifies it as unused, glibc and musl fill it with zero (or leave it untouched), and BSD kernels return whatever was last set with settimeofday(), normally zero. The result was an offset of zero (or garbage) and log timestamps in the wrong zone on every non-Linux build. Derive the offset from the C library's own conversion instead: the difference between localtime_r() and gmtime_r() of the same instant, with day/year straddles handled, and the DST hour removed so that the value has the same meaning as the 'timezone' global on Linux -- standard-time seconds west of UTC -- which is what nolocks_localtime() and formatTimezone() expect (they add 3600 * daylight_active themselves). No platform-specific extensions (tm_gmtoff, timegm) are used. Verified on Linux by comparing the new computation against glibc's 'timezone' for 14 zones (half-hour and 45-minute offsets, southern-hemisphere DST, year boundary) at four instants: identical, except Lord Howe Island, whose DST shift is 30 minutes; there the new code yields the correct displayed time under the caller's fixed 3600-second DST assumption, where 'timezone' would not. Found by compiling the server with Emscripten (musl), where the log timestamps read '-1057815 Jan 1970'. Signed-off-by: Rain Valentine <rsg000@gmail.com>
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Included review availability: Your plan provides up to 10 included reviews per hour; 8 remain after this review. 📝 WalkthroughWalkthroughThe change replaces separate timezone and daylight-saving state with timestamp-specific UTC offsets. The server caches the offset atomically, uses it for local time conversion and ISO 8601 logging, and adds unit and integration coverage. ChangesTimezone offset flow
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~25 minutes Sequence Diagram(s)sequenceDiagram
participant CachedTime
participant OffsetCalculator
participant ServerOffset
participant Logger
CachedTime->>OffsetCalculator: calculate offset for server.unixtime
OffsetCalculator-->>ServerOffset: store UTC offset
Logger->>ServerOffset: load cached offset
Logger->>Logger: convert local time and format ISO 8601 offset
Suggested reviewers: Merge Risk: ⚪ Minimal · up to The timestamp offset change is ready to merge; no actionable correctness or availability risk remains. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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Extract the computation into getTimeZoneFromLocaltime(time_t), which is compiled on every platform, so it can be tested on Linux CI even though getTimeZone() itself uses the 'timezone' global there. The test sets TZ to twelve zones (half-hour and 45-minute offsets, both hemispheres' DST, the furthest east and west) and checks the result at four instants: January and July (opposite DST states per hemisphere) and two instants where the local and UTC dates straddle a year boundary. On Linux and Solaris it additionally checks agreement with the 'timezone' global. Removing the DST adjustment makes 29 of the checks fail. Signed-off-by: Rain Valentine <rsg000@gmail.com>
Signed-off-by: Rain Valentine <rsg000@gmail.com>
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## unstable #4677 +/- ##
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+ Coverage 80.28% 80.65% +0.36%
============================================
Files 191 192 +1
Lines 98345 100884 +2539
============================================
+ Hits 78958 81366 +2408
- Misses 19387 19518 +131
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Review found that inferring the offset as 'standard offset + 3600 * tm_isdst' is wrong for zones whose DST is not a one-hour step forward, and this was true of the existing Linux code as well, not only the portable branch: - Europe/Dublin: tzdata models Irish winter as negative DST (tm_isdst=1 with offset +00:00, standard +01:00). The old formula rendered winter log timestamps at UTC+2 for a wall clock of UTC. - Australia/Lord_Howe: DST is 30 minutes; the old formula added 60. Replace the (timezone, daylight_active) pair with one cached value, server.utc_offset: the actual offset of local time east of UTC, computed by utcOffsetFromLocaltime() from localtime_r/gmtime_r of the same instant and refreshed where daylight_active used to be refreshed (updateCachedTime, once per second from serverCron and at init). nolocks_localtime() and formatTimezone() take that offset directly. This also removes the last use of the Linux-only 'timezone' global, so getTimeZone() and its platform #if go away. The unit test now asserts actual offsets per zone and season -- including Dublin and Lord Howe -- and that nolocks_localtime() fed with the cached offset reproduces localtime_r's wall clock. Live check: with TZ=Europe/Dublin and TZ=Australia/Lord_Howe the server's ISO-8601 log timestamps now match the C library's. Signed-off-by: Rain Valentine <rsg000@gmail.com>
Signed-off-by: Rain Valentine <rsg000@gmail.com>
Cover the parts of the change the unit test for utcOffsetFromLocaltime() did not reach: formatTimezone() rendering offsets with minutes (+10:30, -03:30, +05:45), updateCachedTime() publishing the offset the logger reads, and, via a Tcl test that starts the server under Australia/Lord_Howe, Europe/Dublin and America/St_Johns, the ISO 8601 log line itself carrying the actual local offset. Also fix the stale comment on tzset() in main(). Signed-off-by: Rain Valentine <rsg000@gmail.com>
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ccov CI job failure is known flaky test #4153 |
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September 16, 2026 05:18
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Actionable comments posted: 1
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Inline comments:
In `@src/unit/test_util.cpp`:
- Line 408: Replace both std::string saved declarations in the affected tests
with sds-based saved TZ values, and free each allocation after restoring TZ.
Apply the change consistently to both tests while preserving their existing
timezone save-and-restore behavior.
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src/localtime.csrc/server.csrc/server.hsrc/unit/test_util.cppsrc/util.csrc/util.htests/integration/logging.tcl
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src/unit/README.md asks for tests any C developer can read: no std::string, no range-for over references or initializer lists. Save the caller's TZ in an sds and iterate with plain index loops. Signed-off-by: Rain Valentine <rsg000@gmail.com>
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Inline comments:
In `@src/unit/test_util.cpp`:
- Line 482: In the time-zone loop around zones[i], add the existing non-UTC
fallback check used by TestUtcOffsetFromLocaltime before updateCachedTime(1),
skipping unavailable zones before validating cached offsets. Preserve the
current expected-value and utcOffsetFromLocaltime(now) checks for available
zones.
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On a host whose tz database lacks a zone, localtime_r() falls back to UTC for both sides of the comparison, so TestUpdateCachedTimeRefreshesUtcOffset passed without covering any of its zones. Share the probe with TestUtcOffsetFromLocaltime as tzKnownToHost(), and report GTEST_SKIP when only UTC was covered instead of a vacuous pass. Signed-off-by: Rain Valentine <rsg000@gmail.com>
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getTimeZone()read the obsoletetzargument ofgettimeofday()on every platform but Linux/Solaris. POSIX specifies it as unused; glibc/musl zero it, BSD returns stalesettimeofday()state. Result: zero or garbage log-timestamp offsets on non-Linux builds (found via Emscripten/musl:-1057815 Jan 1970).The Linux path had a related but separate bug: caching
timezone(standard offset) plus adaylight_activeflag and adding a fixed 3600s for DST is wrong wherever DST isn't a flat one-hour step. Affects Europe/Dublin (tzdata models winter as negative DST: tm_isdst=1 at UTC+0) and Australia/Lord_Howe (30-minute DST) — both computed the wrong offset year-round or seasonally.Replace both with
utcOffsetFromLocaltime(): the actual UTC offset, DST included, from the difference betweenlocaltime_r()andgmtime_r()of the same instant. No platform-specific extensions (tm_gmtoff, timegm), notimezoneglobal. Cached once per second inserver.utc_offset, same refresh point the olddaylight_activeused; consumed lock-free bynolocks_localtime()andformatTimezone()exactly as before.Verified against glibc's
timezonefor 14 zones (half/45-min offsets, southern DST, year boundary) at 4 instants — identical except Dublin and Lord Howe, where the new code is the one that's actually correct.User-visible: log timestamp offset changes on non-Linux builds (was 0/garbage), and on Linux only for Europe/Dublin and Australia/Lord_Howe (was wrong). All other zones on Linux: byte-identical output.