feat(quotas): Add an opportunistic cache for Quotas #5416
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loewenheim
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| let max_allowed_spend = usize::try_from(remaining).unwrap_or(usize::MAX) | ||
| * PERCENT_PRECISION | ||
| / self.max_over_spend_divisor.get(); |
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IIUC this is essentially remaining * max_over_spend_percentage (the PERCENT_PRECISIONs cancel out). It might be worth factoring this differently because currently it's quite difficult to understand.
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There is some docs on PERCENT_PRECISION to problem is the accuracy loss going from 0..1 percentage to an integer division.
1 / 0.7 = 1.42, which would truncate to 1 when converting to usize. To keep some precision it's multiplied by 10 first.
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loewenheim
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loewenheim
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Implements an opportunistic quota cache. Closes: INGEST-638.
The cache is aware of the currently used quota and opportunistically accepts N% of the remaining quota before synchronizing with the central cache (Redis).
By default the cache is not enabled. I plan to test the cache and collect some telemetry in a test environment.
In a follow up I want to re-evaluate how the percentage is calculated and potentially do it normalized as a percentage of 1 second or 10 seconds, to not run into issues with very large quota windows.
I had to change how the quantity is handled, I added the
quantityto theRedisQuotainstead of carrying int separately, this makes it possible for the cache easily to work per quota. All the underlying machinery already worked per quota, making this a very simple refactor.