Merge 0bd3431b88 into a44e44b980

litellm/proxy/common_utils/scheduled_job_stagger.py

@@ -33,7 +33,7 @@ import hashlib
 import os
 import socket
 from collections.abc import Callable, Mapping, Sequence
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from types import MappingProxyType
 from typing import Final, Protocol
 
@@ -108,6 +108,20 @@ class JobSubmission(Protocol):
     def scheduled_run_times(self) -> Sequence[datetime]: ...
 
 
+def _shift_datetime(dt: datetime, delta: timedelta) -> datetime:
+    """
+    Shift a datetime by delta preserving absolute time (timeline) arithmetic.
+
+    Standard `datetime - delta` on timezone-aware datetimes resets `fold = 0` during
+    ambiguous hours (such as DST fall-back). Converting to UTC before arithmetic and
+    then converting back to the source tzinfo ensures the shift operates on absolute
+    time and preserves fold and correct fire ordering.
+    """
+    if dt.tzinfo is None:
+        return dt + delta
+    return (dt.astimezone(timezone.utc) + delta).astimezone(dt.tzinfo)
+
+
 class _OffsetTrigger:
     """
     Delegates to ``base`` on a clock rolled back by ``offset``, then rolls the answer
@@ -125,9 +139,11 @@ class _OffsetTrigger:
         self.offset = offset
 
     def get_next_fire_time(self, previous_fire_time: datetime | None, now: datetime) -> datetime | None:
-        shifted_previous: Final = None if previous_fire_time is None else previous_fire_time - self.offset
-        next_fire_time: Final = self.base.get_next_fire_time(shifted_previous, now - self.offset)
-        return None if next_fire_time is None else next_fire_time + self.offset
+        shifted_previous: Final = (
+            None if previous_fire_time is None else _shift_datetime(previous_fire_time, -self.offset)
+        )
+        next_fire_time: Final = self.base.get_next_fire_time(shifted_previous, _shift_datetime(now, -self.offset))
+        return None if next_fire_time is None else _shift_datetime(next_fire_time, self.offset)
 
     def __str__(self) -> str:
         return f"{self.base}[+{int(self.offset.total_seconds())}s]"

tests/unit/proxy/common_utils/test_scheduled_job_stagger.py

@@ -3,6 +3,7 @@ import logging
 import os
 from datetime import datetime, timedelta, timezone
 from types import SimpleNamespace
+from zoneinfo import ZoneInfo
 
 import pytest
 from apscheduler.executors.asyncio import AsyncIOExecutor
@@ -14,6 +15,8 @@ from apscheduler.triggers.interval import IntervalTrigger
 from litellm.constants import PTU_ROLLUP_JOB_ID, PTU_ROLLUP_LOCK_TTL_SECONDS
 from litellm.proxy._types import ScheduledJobStaggerSettings
 from litellm.proxy.common_utils.scheduled_job_stagger import (
+    _OffsetTrigger,
+    _shift_datetime,
     apply_scheduled_job_stagger,
     attach_job_timing_logger,
     offset_seconds,
@@ -309,3 +312,29 @@ def test_job_timing_is_logged_with_scheduled_and_actual_start(caplog):
     assert f"scheduled_run_time={scheduled.isoformat()}" in message
     assert "actual_start_time=" in message
     assert "delay=2." in message
+
+
+def test_offset_trigger_handles_dst_fall_back_without_looping():
+    """Regression test for #48286: during DST fall-back (fold=1), shifted time must not land in fold=0 and loop."""
+    tz = ZoneInfo("Europe/Paris")
+    base = IntervalTrigger(seconds=60, timezone=tz)
+    trigger = _OffsetTrigger(base, timedelta(seconds=30))
+
+    # Test normal CEST, DST fall-back hour (fold=1), and normal CET
+    for label, now in [
+        ("01:30 CEST", datetime(2026, 10, 25, 1, 30, tzinfo=tz)),
+        ("02:30 CET (repeated hour)", datetime(2026, 10, 25, 2, 30, fold=1, tzinfo=tz)),
+        ("03:30 CET", datetime(2026, 10, 25, 3, 30, tzinfo=tz)),
+    ]:
+        nrt = datetime.fromtimestamp(now.timestamp() - 90, tz)
+        count = 0
+        while nrt and nrt.astimezone(timezone.utc) <= now.astimezone(timezone.utc) and count < 100:
+            count += 1
+            nrt = trigger.get_next_fire_time(nrt, now)
+        assert count == 2, f"Failed for {label}: count={count}"
+
+
+def test_shift_datetime_handles_naive_and_timezone_aware():
+    naive = datetime(2026, 1, 1, 12, 0, 0)
+    assert _shift_datetime(naive, timedelta(seconds=10)) == datetime(2026, 1, 1, 12, 0, 10)
+    assert _shift_datetime(naive, -timedelta(seconds=10)) == datetime(2026, 1, 1, 11, 59, 50)