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Diffstat (limited to 'vendor/github.com/uber/jaeger-client-go/utils/rate_limiter.go')
-rw-r--r-- | vendor/github.com/uber/jaeger-client-go/utils/rate_limiter.go | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/vendor/github.com/uber/jaeger-client-go/utils/rate_limiter.go b/vendor/github.com/uber/jaeger-client-go/utils/rate_limiter.go new file mode 100644 index 000000000..1b8db9758 --- /dev/null +++ b/vendor/github.com/uber/jaeger-client-go/utils/rate_limiter.go @@ -0,0 +1,77 @@ +// Copyright (c) 2017 Uber Technologies, Inc. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +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 +} |