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I noticed that inside the function adjustavailableTokens()
func (tb *Bucket) adjustavailableTokens(tick int64) {
if tb.availableTokens >= tb.capacity {
return
}
tb.availableTokens += (tick - tb.latestTick) * tb.quantum
if tb.availableTokens > tb.capacity {
tb.availableTokens = tb.capacity
}
tb.latestTick = tick
return
}the tb.latestTick is not updated if tb.availableTokens >= tb.capacity。
That makes the description of the variable latestTick holds the latest tick for which we know the number of tokens in the bucket. not so accurate, IMO.
And I wrote a snippet of code which can produce surprising results:
func main() {
bucket := ratelimit.NewBucketWithQuantum(time.Second*1, 100, 20)
fmt.Printf("Avail=%d\n", bucket.Available())
fmt.Printf("%v\n", time.Now())
fmt.Printf("Pause wait for 5s\n")
time.Sleep(time.Second * 5)
fmt.Printf("%v\n", time.Now())
fmt.Printf("Avail=%d\n", bucket.Available())
fmt.Printf("Request token up to 100\n")
cnt := bucket.TakeAvailable(100)
fmt.Printf("Token taken=%d\n", cnt)
// It will surprise you.
fmt.Printf("Avail=%d\n", bucket.Available())
}Output
Avail=100
2019-09-26 01:12:47.9410106 +0800 CST m=+0.003992001 Pause wait for 5s
2019-09-26 01:12:52.9614404 +0800 CST m=+5.024421801 Avail=100
Request token up to 100
Token taken=100
Avail=100
That is, after taken all tokens out of the bucket, the bucket is still full.
Is this by design or just an implementation bug?
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