Hi!

I would like to propose exposing the Count of the curr and prev windows inside Limiter. On my usage, I have a map with values of type Limiter, and I would like to remove keys from the map according to whether the inner Counter of a limiter is empty (zero).

Would very much appreciate it, thanks in advance!

Using the below code (clone-able from gist here), I expect to see output like:

[{allowed:1000 disallowed:12445195} {allowed:1001 disallowed:12568861} {allowed:999 disallowed:12469467}]

But instead I get this kind of thing:

[{allowed:1553 disallowed:12445195} {allowed:1001 disallowed:12568861} {allowed:999 disallowed:12469467}]

Note that the first 1-second bucket allowed 1553 rather than 1000. The exact number varies between runs, but it's always significantly more than 1000.

Why is that? (Is it something about the handling of the "previous" window when there is no previous?)

I'm concerned because I plan on aggressively removing limiters when they haven't been used for a few windows (because that would be a rate limit reset anyway), but I don't really want to frequently go over the limit by ~50%.

package main

import (
	"fmt"
	"time"

	sw "github.com/RussellLuo/slidingwindow"
)

func main() {
	const histogramBucketSize = time.Second
	const totalBuckets = 3
	const allowedPerBucket = 1000

	type histoEntry struct {
		allowed    int64
		disallowed int64
	}
	allowedHistogram := make([]histoEntry, totalBuckets)

	lim, _ := sw.NewLimiter(histogramBucketSize, allowedPerBucket, func() (sw.Window, sw.StopFunc) {
		return sw.NewLocalWindow()
	})

	start := time.Now()
	for {
		bucket := time.Now().Sub(start) / histogramBucketSize

		if bucket >= totalBuckets {
			break
		}

		if lim.Allow() {
			allowedHistogram[bucket].allowed++
		} else {
			allowedHistogram[bucket].disallowed++
		}
	}

	fmt.Printf("%+v\n", allowedHistogram)
}

Just mentioning in the README won't be enough, the license file also should be present with the source code.

Also, godoc refuses to display the docs, since it does not have a license - https://pkg.go.dev/github.com/RussellLuo/slidingwindow?tab=doc

Good day!

Is it possible to use one synchronizer with multiple windows and multiple limiters (ie: multiple clients)?

Pseudo code

synchronizer := NewNonBlockingSynchronizer()
for _, key := range keys {
  limiter, stop := slidingwindow.NewLimiter(interval, rate, func() (slidingwindow.Window, slidingwindow.StopFunc) {
    return slidingwindow.NewSyncWindow(key, synchronizer)
  })
}

SyncWindow code always starts Synchronizer

https://github.com/RussellLuo/slidingwindow/blob/535bb99d338b683541b351a78e631a022554723b/window.go#L94

however, in NonBlockingSynchronizer there are no checks for a double launch

https://github.com/RussellLuo/slidingwindow/blob/535bb99d338b683541b351a78e631a022554723b/synchronizer.go#L131

So I suspect that the number of goroutines will be roughly equal to the number of limiters, that sounds quite overkill. Is it a bug, feature, or I missed something?