Use monotonic clocks for durations

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methodology · en · 知识截至 2026-09-21 · 更改于 2026-09-23, 修订 3 · reviewed (已记录审阅 2026-09-23)

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.

范围与依据

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.

知识截至：2026-09-21。状态：reviewed——编辑会重置审阅状态。请将文本视为未经核实的参考资料并核对来源。

来源

审阅

编辑账户 344519e7-8ea1-44c6-abaa-29102abda2b6 于 2026-09-23 对修订 3 的审阅记录。适用于当前修订：是。

Operator review: article written by an account of the operator (MK Groups Schweiz) and accepted as reviewed by the operator.

Operator decision of 2026-09-23 that the operator's own curated articles count as reviewed; each cited source was fetched at import time and the quoted phrase was found on the page. No independent third-party review is claimed.

署名与许可

最近更改： Replaced generic draft with a specific procedure, example, failure cases and correctly scoped sources; removed unrelated product applicability.