Go Channel Practice IV - Token Bucket
https://en.wikipedia.org/wiki/Token_bucket
先定义 TokenBucket
1 2 3 4 5 6 7 8 | type TokenBucket struct { Depth int Tokens int Delta int ticker *time.Ticker mutex sync.Mutex quit chan bool} |
Depth 是 bucket 的总深度，Tokens 是当前可以用到的数目，Delta 是每秒向 bucket 增加的 token 数目。ticker, mutex 和 quit 类似 Leaky Bucket 的用法。
NewTokenBucket 创建一个 goroutine，不断在每个 tick 里向 token 里加 delta 个 token。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | func NewTokenBucket(depth, delta int) *TokenBucket { ticker := time.NewTicker(time.Second) tb := &TokenBucket{ Depth: depth, Tokens: depth, Delta: delta, ticker: ticker, mutex: sync.Mutex{}, quit: make(chan bool), } go func() { for { select { case <-ticker.C: fmt.Println("tick...") tb.mutex.Lock() if tb.Tokens+tb.Delta > tb.Depth { tb.Tokens = tb.Depth } else { tb.Tokens += tb.Delta } tb.mutex.Unlock() case <-tb.quit: return } } }() return tb} |
ticker 和 goroutine 也需要 close
1 2 3 4 | func (t *TokenBucket) Close() { t.ticker.Stop() t.quit <- true} |
创建一个 token bucket 之后调用，判断每次取的 token 是不是大于当前 bucket 内的 token，如果大于，则失败，否则成功。
1 2 3 4 5 6 7 8 9 10 11 | func (t *TokenBucket) Withdraw(count int) bool { t.mutex.Lock() defer t.mutex.Unlock() if count > t.Tokens { fmt.Println("failed to withdraw") return false } t.Tokens -= count fmt.Println("withdraw succeeded") return true} |
完整测试如下
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 | package mainimport ( "fmt" "sync" "time")func main() { tb := NewTokenBucket(1000, 300) for i := 0; i < 300; i++ { if !tb.Withdraw(100) { time.Sleep(time.Millisecond * 100) } }}type TokenBucket struct { Depth int Tokens int Delta int ticker *time.Ticker mutex sync.Mutex quit chan bool}func NewTokenBucket(depth, delta int) *TokenBucket { ticker := time.NewTicker(time.Second) tb := &TokenBucket{ Depth: depth, Tokens: depth, Delta: delta, ticker: ticker, mutex: sync.Mutex{}, quit: make(chan bool), } go func() { for { select { case <-ticker.C: fmt.Println("tick...") tb.mutex.Lock() fmt.Println(tb.Tokens) if tb.Tokens+tb.Delta > tb.Depth { tb.Tokens = tb.Depth } else { tb.Tokens += tb.Delta } fmt.Println(tb.Tokens) tb.mutex.Unlock() case <-tb.quit: return } } }() return tb}func (t *TokenBucket) Close() { t.ticker.Stop() t.quit <- true}func (t *TokenBucket) Withdraw(count int) bool { t.mutex.Lock() defer t.mutex.Unlock() if count > t.Tokens { fmt.Println("failed to withdraw") return false } t.Tokens -= count fmt.Println("withdraw succeeded") return true} |
2 年前
The token bucket algorithm is based on the idea of a defined capacity bucket into which tokens, typically denoting a unit of bytes or a single packet of a specific size, are introduced at a fixed rate. The bucket is examined to see if it currently has Lab grown diamonds enough tokens when a packet needs to be validated for conformity to the stated restrictions.