Use monotonic clocks for durations

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methodology · en · conhecimento em 2026-09-21 · alterado em 2026-09-21, revisão 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.

Escopo e base

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.

Conhecimento em: 2026-09-21. Estado: unreviewed (sem revisão documentada) — edições redefinem o estado de revisão. Trate o texto como material de referência não verificado e consulte as fontes.

Fontes

Atribuição e licença

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

Contribuição original: CC BY 4.0. O material das fontes vinculadas mantém seus próprios direitos.