Bug 1751402 - Guarantee getMonotonicNow doesn't return a negative value #1130
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badboy
approved these changes
Jan 27, 2022
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Oops, sorry I didn't get to this yesterday as I planned. Is it the storage that's responsible for setting the first event's timestamp to 0, then? |
No worries, jan-erik asked about it that is why I marked him as reviewer :D
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We were previously extracting the TIME_ORIGIN from Date.now() in case performance.now was not available in the environment. That could create negative timestamps, because Date.now is not guaranteed to be monotonically increasing. (Yeah... it is contradictiory to have a function called getMonotonicNow, but not guarantee monotonically increasing timestamps for some platforms. At least there is a TODO comment to address the incoherence at some point). Subtracting the TIME_ORIGIN was essentially pointless and I don't really know why that was the case before. That function is used by the Timestamp metric type and for event timestamps which are both about elapsed time. EXTRA: Address stray TODO comment on TimespanMetricType test suite.
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We were previously extracting the TIME_ORIGIN from Date.now()
in case performance.now was not available in the environment.
That could create negative timestamps, because Date.now is not
guaranteed to be monotonically increasing. (Yeah... it is
contradictiory to have a function called getMonotonicNow, but not
guarantee monotonically increasing timestamps for some platforms.
At least there is a TODO comment to address the incoherence at
some point).
Subtracting the TIME_ORIGIN was essentially pointless and I don't really
know why that was the case before. That function is used by the Timestamp
metric type and for event timestamps which are both about elapsed time,
so the absoulte timestamp should not matter.
EXTRA: Address stray TODO comment on TimespanMetricType test suite.
Pull Request checklist
glean/folder, run:npm run testRuns all testsnpm run lintRuns all lintersTests: This PR includes thorough tests or an explanation of why it does notCHANGELOG.mdor an explanation of why it does not need oneDocumentation: This PR includes documentation changes, an explanation of why it does not need that or a follow-up bug has been filed to do that work