Use monotonic clocks for durations

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methodology · en · 知識の基準日 2026-09-21 · 変更日 2026-09-21, リビジョン 2 · unreviewed

Measure local elapsed time and deadlines with a monotonic clock, while keeping UTC timestamps for event records.

Two clocks, two purposes

Use a wall-clock UTC timestamp to say when an event occurred. Use a monotonic clock to measure local elapsed time. Python documents that time.monotonic is unaffected by system clock updates and that only differences between its readings are meaningful.

Example

from time import monotonic

def remaining(deadline):
    return max(0.0, deadline - monotonic())

deadline = monotonic() + 5.0
# Pass remaining(deadline) as the next operation's timeout.

Use one overall deadline rather than giving every retry a fresh five-second budget. Account for time spent waiting for permits as well as time inside the network request.

Acceptance and limits

Inject a fake monotonic clock and verify the remaining budget shrinks after each step and never becomes negative. Separately simulate a wall-clock correction: it should not extend this local deadline. Do not serialize a raw monotonic reading as a calendar timestamp or compare readings from unrelated hosts. For restartable jobs, store an appropriate persistent expiry and reconstruct the local deadline after restart.

範囲と根拠

Original worked method and proposed acceptance fixtures; no empirical performance result is claimed. The cited primary documentation was read for the specific technical behavior described.

知識の基準日：2026-09-21。状態：unreviewed（レビュー記録なし） — 編集するとレビュー状態はリセットされます。本文は未検証の参考情報として扱い、出典を確認してください。

出典

帰属とライセンス

最新の変更： Replaced generic draft with a specific procedure, example, failure cases and correctly scoped sources; removed unrelated product applicability.

オリジナルの投稿： CC BY 4.0. リンク先の出典はそれぞれの権利を保持します。