traefik/vendor/github.com/uber/jaeger-client-go/utils/rate_limiter.go
2018-01-10 17:48:04 +01:00

83 lines
3.4 KiB
Go

// Copyright (c) 2016 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package utils
import (
"sync"
"time"
)
// RateLimiter is a filter used to check if a message that is worth itemCost units is within the rate limits.
type RateLimiter interface {
CheckCredit(itemCost float64) bool
}
type rateLimiter struct {
sync.Mutex
creditsPerSecond float64
balance float64
maxBalance float64
lastTick time.Time
timeNow func() time.Time
}
// NewRateLimiter creates a new rate limiter based on leaky bucket algorithm, formulated in terms of a
// credits balance that is replenished every time CheckCredit() method is called (tick) by the amount proportional
// to the time elapsed since the last tick, up to max of creditsPerSecond. A call to CheckCredit() takes a cost
// of an item we want to pay with the balance. If the balance exceeds the cost of the item, the item is "purchased"
// and the balance reduced, indicated by returned value of true. Otherwise the balance is unchanged and return false.
//
// This can be used to limit a rate of messages emitted by a service by instantiating the Rate Limiter with the
// max number of messages a service is allowed to emit per second, and calling CheckCredit(1.0) for each message
// to determine if the message is within the rate limit.
//
// It can also be used to limit the rate of traffic in bytes, by setting creditsPerSecond to desired throughput
// as bytes/second, and calling CheckCredit() with the actual message size.
func NewRateLimiter(creditsPerSecond, maxBalance float64) RateLimiter {
return &rateLimiter{
creditsPerSecond: creditsPerSecond,
balance: maxBalance,
maxBalance: maxBalance,
lastTick: time.Now(),
timeNow: time.Now}
}
func (b *rateLimiter) CheckCredit(itemCost float64) bool {
b.Lock()
defer b.Unlock()
// calculate how much time passed since the last tick, and update current tick
currentTime := b.timeNow()
elapsedTime := currentTime.Sub(b.lastTick)
b.lastTick = currentTime
// calculate how much credit have we accumulated since the last tick
b.balance += elapsedTime.Seconds() * b.creditsPerSecond
if b.balance > b.maxBalance {
b.balance = b.maxBalance
}
// if we have enough credits to pay for current item, then reduce balance and allow
if b.balance >= itemCost {
b.balance -= itemCost
return true
}
return false
}