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Fix no slack option for int64 based option #95

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Merged
rabbbit merged 1 commit into from
Jul 13, 2022
Merged

Fix no slack option for int64 based option #95

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11 changes: 4 additions & 7 deletions limiter_atomic_int64.go
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Original file line number Diff line number Diff line change
Expand Up @@ -66,10 +66,10 @@ func (t *atomicInt64Limiter) Take() time.Time {
timeOfNextPermissionIssue := atomic.LoadInt64(&t.state)

switch {
case timeOfNextPermissionIssue == 0:
// If this is our first request, then we allow it.
case timeOfNextPermissionIssue == 0 || (t.maxSlack == 0 && now-timeOfNextPermissionIssue > int64(t.perRequest)):
// if this is our first call or t.maxSlack == 0 we need to shrink issue time to now
newTimeOfNextPermissionIssue = now
case now-timeOfNextPermissionIssue > int64(t.maxSlack):
case t.maxSlack > 0 && now-timeOfNextPermissionIssue > int64(t.maxSlack):
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@rabbbit rabbbit Jul 13, 2022

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Suggested change
case t.maxSlack > 0 && now-timeOfNextPermissionIssue > int64(t.maxSlack):
now-timeOfNextPermissionIssue > int64(t.maxSlack):

I think the maxSlack check here is unnecessary - the previous iff should have covered that.

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@rabbbit rabbbit Jul 13, 2022

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Wait, no, this is wrong - > int64(t.maxSlack): vs > int64(t.perRequest)).

I clearly need to understand this code more.

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@storozhukBM storozhukBM Jul 13, 2022

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I think there can be a case where t.maxSlack == 0 is true, but now-timeOfNextPermissionIssue > int64(t.perRequest) is false, in that case we will try to evaluate now-timeOfNextPermissionIssue > int64(t.maxSlack) and it can be true, so we will end up in a wrong branch. So we need t.maxSlack > 0 check here to step into default branch.

// a lot of nanoseconds passed since the last Take call
// we will limit max accumulated time to maxSlack
newTimeOfNextPermissionIssue = now - int64(t.maxSlack)
Expand All @@ -82,9 +82,6 @@ func (t *atomicInt64Limiter) Take() time.Time {
break
}
}
nanosToSleepUntilOurPermissionIsIssued := newTimeOfNextPermissionIssue - now
if nanosToSleepUntilOurPermissionIsIssued > 0 {
t.clock.Sleep(time.Duration(nanosToSleepUntilOurPermissionIsIssued))
}
t.clock.Sleep(time.Duration(newTimeOfNextPermissionIssue - now))
return time.Unix(0, newTimeOfNextPermissionIssue)
}