[RateLimiter] Fix SlidingWindow calculations #47557
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fabpot
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…oeny) This PR was squashed before being merged into the 6.4 branch. Discussion ---------- [RateLimiter] Add SlidingWindowLimiter::reserve() | Q | A | ------------- | --- | Branch? | 6.4 | Bug fix? | yes | New feature? | yes | Deprecations? | yes | Tickets | Fix #40289, Fixes #46875 | License | MIT This implements `LimiterInterface->reserve()` for `SlidingWindowLimiter`. I'm not sure if the lack of implementation was due to time/scope or if it's actually not possible and my approach is incorrect. But I like to give it a try anyway. Perhaps `@wouterj` you could elaborate on that? The calculation does the following: 1. Calculate tokens to be released within this window. E.g. if 4 were used in the last window, at 50% into the current, 2 are still to be released. 2. Calculate the time-per-token within the remainder of the window. If the requested tokens will be available before the end of the current window, return the time-per-token * needed-tokens. 3. Otherwise return time-per-token of the regular interval * needed-tokens(-after the current window). This wasn't a [bugfix](#51592), so back to feature PR. I couldn't reopen #47557, So had to create this new PR. Commits ------- 1b4a2df [RateLimiter] Add SlidingWindowLimiter::reserve()
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This implements
LimiterInterface->reserve()forSlidingWindowLimiter. I'm not sure if the lack of implementation was due to time/scope or if it's actually not possible and my approach is incorrect. But I like to give it a try anyway. Perhaps @wouterj you could elaborate on that?The calculation does the following:
Some other things I've noticed in the RateLimiter:
FixedWindowLimiteruses aWindowclass, whereasSlidingWindowLimiteruses aSlidingWindow. Shouldn't the first have aFixedWindowclass?Windowclass takes its$windowSizeas argument,SlidingWindowdoes not. Perhaps the latter could also take this argument in this PR, since it's used in the calculation. But I guess those classes have to be backwards compatible.SlidingWindow->getRetryAfter()is no longer used and could be deprecated in favor ofcalculateTimeForTokens. Making it more like the fixed window.Edit: This should fix #40289, I've added it to the QA table.