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-rw-r--r--vendor/github.com/juju/ratelimit/ratelimit.go284
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diff --git a/vendor/github.com/juju/ratelimit/ratelimit.go b/vendor/github.com/juju/ratelimit/ratelimit.go
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--- a/vendor/github.com/juju/ratelimit/ratelimit.go
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-// Copyright 2014 Canonical Ltd.
-// Licensed under the LGPLv3 with static-linking exception.
-// See LICENCE file for details.
-
-// Package ratelimit provides an efficient token bucket implementation
-// that can be used to limit the rate of arbitrary things.
-// See http://en.wikipedia.org/wiki/Token_bucket.
-package ratelimit
-
-import (
- "math"
- "strconv"
- "sync"
- "time"
-)
-
-// Bucket represents a token bucket that fills at a predetermined rate.
-// Methods on Bucket may be called concurrently.
-type Bucket struct {
- startTime time.Time
- capacity int64
- quantum int64
- fillInterval time.Duration
- clock Clock
-
- // The mutex guards the fields following it.
- mu sync.Mutex
-
- // avail holds the number of available tokens
- // in the bucket, as of availTick ticks from startTime.
- // It will be negative when there are consumers
- // waiting for tokens.
- avail int64
- availTick int64
-}
-
-// Clock is used to inject testable fakes.
-type Clock interface {
- Now() time.Time
- Sleep(d time.Duration)
-}
-
-// realClock implements Clock in terms of standard time functions.
-type realClock struct{}
-
-// Now is identical to time.Now.
-func (realClock) Now() time.Time {
- return time.Now()
-}
-
-// Sleep is identical to time.Sleep.
-func (realClock) Sleep(d time.Duration) {
- time.Sleep(d)
-}
-
-// NewBucket returns a new token bucket that fills at the
-// rate of one token every fillInterval, up to the given
-// maximum capacity. Both arguments must be
-// positive. The bucket is initially full.
-func NewBucket(fillInterval time.Duration, capacity int64) *Bucket {
- return NewBucketWithClock(fillInterval, capacity, realClock{})
-}
-
-// NewBucketWithClock is identical to NewBucket but injects a testable clock
-// interface.
-func NewBucketWithClock(fillInterval time.Duration, capacity int64, clock Clock) *Bucket {
- return NewBucketWithQuantumAndClock(fillInterval, capacity, 1, clock)
-}
-
-// rateMargin specifes the allowed variance of actual
-// rate from specified rate. 1% seems reasonable.
-const rateMargin = 0.01
-
-// NewBucketWithRate returns a token bucket that fills the bucket
-// at the rate of rate tokens per second up to the given
-// maximum capacity. Because of limited clock resolution,
-// at high rates, the actual rate may be up to 1% different from the
-// specified rate.
-func NewBucketWithRate(rate float64, capacity int64) *Bucket {
- return NewBucketWithRateAndClock(rate, capacity, realClock{})
-}
-
-// NewBucketWithRateAndClock is identical to NewBucketWithRate but injects a
-// testable clock interface.
-func NewBucketWithRateAndClock(rate float64, capacity int64, clock Clock) *Bucket {
- for quantum := int64(1); quantum < 1<<50; quantum = nextQuantum(quantum) {
- fillInterval := time.Duration(1e9 * float64(quantum) / rate)
- if fillInterval <= 0 {
- continue
- }
- tb := NewBucketWithQuantumAndClock(fillInterval, capacity, quantum, clock)
- if diff := math.Abs(tb.Rate() - rate); diff/rate <= rateMargin {
- return tb
- }
- }
- panic("cannot find suitable quantum for " + strconv.FormatFloat(rate, 'g', -1, 64))
-}
-
-// nextQuantum returns the next quantum to try after q.
-// We grow the quantum exponentially, but slowly, so we
-// get a good fit in the lower numbers.
-func nextQuantum(q int64) int64 {
- q1 := q * 11 / 10
- if q1 == q {
- q1++
- }
- return q1
-}
-
-// NewBucketWithQuantum is similar to NewBucket, but allows
-// the specification of the quantum size - quantum tokens
-// are added every fillInterval.
-func NewBucketWithQuantum(fillInterval time.Duration, capacity, quantum int64) *Bucket {
- return NewBucketWithQuantumAndClock(fillInterval, capacity, quantum, realClock{})
-}
-
-// NewBucketWithQuantumAndClock is identical to NewBucketWithQuantum but injects
-// a testable clock interface.
-func NewBucketWithQuantumAndClock(fillInterval time.Duration, capacity, quantum int64, clock Clock) *Bucket {
- if fillInterval <= 0 {
- panic("token bucket fill interval is not > 0")
- }
- if capacity <= 0 {
- panic("token bucket capacity is not > 0")
- }
- if quantum <= 0 {
- panic("token bucket quantum is not > 0")
- }
- return &Bucket{
- clock: clock,
- startTime: clock.Now(),
- capacity: capacity,
- quantum: quantum,
- avail: capacity,
- fillInterval: fillInterval,
- }
-}
-
-// Wait takes count tokens from the bucket, waiting until they are
-// available.
-func (tb *Bucket) Wait(count int64) {
- if d := tb.Take(count); d > 0 {
- tb.clock.Sleep(d)
- }
-}
-
-// WaitMaxDuration is like Wait except that it will
-// only take tokens from the bucket if it needs to wait
-// for no greater than maxWait. It reports whether
-// any tokens have been removed from the bucket
-// If no tokens have been removed, it returns immediately.
-func (tb *Bucket) WaitMaxDuration(count int64, maxWait time.Duration) bool {
- d, ok := tb.TakeMaxDuration(count, maxWait)
- if d > 0 {
- tb.clock.Sleep(d)
- }
- return ok
-}
-
-const infinityDuration time.Duration = 0x7fffffffffffffff
-
-// Take takes count tokens from the bucket without blocking. It returns
-// the time that the caller should wait until the tokens are actually
-// available.
-//
-// Note that if the request is irrevocable - there is no way to return
-// tokens to the bucket once this method commits us to taking them.
-func (tb *Bucket) Take(count int64) time.Duration {
- d, _ := tb.take(tb.clock.Now(), count, infinityDuration)
- return d
-}
-
-// TakeMaxDuration is like Take, except that
-// it will only take tokens from the bucket if the wait
-// time for the tokens is no greater than maxWait.
-//
-// If it would take longer than maxWait for the tokens
-// to become available, it does nothing and reports false,
-// otherwise it returns the time that the caller should
-// wait until the tokens are actually available, and reports
-// true.
-func (tb *Bucket) TakeMaxDuration(count int64, maxWait time.Duration) (time.Duration, bool) {
- return tb.take(tb.clock.Now(), count, maxWait)
-}
-
-// TakeAvailable takes up to count immediately available tokens from the
-// bucket. It returns the number of tokens removed, or zero if there are
-// no available tokens. It does not block.
-func (tb *Bucket) TakeAvailable(count int64) int64 {
- return tb.takeAvailable(tb.clock.Now(), count)
-}
-
-// takeAvailable is the internal version of TakeAvailable - it takes the
-// current time as an argument to enable easy testing.
-func (tb *Bucket) takeAvailable(now time.Time, count int64) int64 {
- if count <= 0 {
- return 0
- }
- tb.mu.Lock()
- defer tb.mu.Unlock()
-
- tb.adjust(now)
- if tb.avail <= 0 {
- return 0
- }
- if count > tb.avail {
- count = tb.avail
- }
- tb.avail -= count
- return count
-}
-
-// Available returns the number of available tokens. It will be negative
-// when there are consumers waiting for tokens. Note that if this
-// returns greater than zero, it does not guarantee that calls that take
-// tokens from the buffer will succeed, as the number of available
-// tokens could have changed in the meantime. This method is intended
-// primarily for metrics reporting and debugging.
-func (tb *Bucket) Available() int64 {
- return tb.available(tb.clock.Now())
-}
-
-// available is the internal version of available - it takes the current time as
-// an argument to enable easy testing.
-func (tb *Bucket) available(now time.Time) int64 {
- tb.mu.Lock()
- defer tb.mu.Unlock()
- tb.adjust(now)
- return tb.avail
-}
-
-// Capacity returns the capacity that the bucket was created with.
-func (tb *Bucket) Capacity() int64 {
- return tb.capacity
-}
-
-// Rate returns the fill rate of the bucket, in tokens per second.
-func (tb *Bucket) Rate() float64 {
- return 1e9 * float64(tb.quantum) / float64(tb.fillInterval)
-}
-
-// take is the internal version of Take - it takes the current time as
-// an argument to enable easy testing.
-func (tb *Bucket) take(now time.Time, count int64, maxWait time.Duration) (time.Duration, bool) {
- if count <= 0 {
- return 0, true
- }
- tb.mu.Lock()
- defer tb.mu.Unlock()
-
- currentTick := tb.adjust(now)
- avail := tb.avail - count
- if avail >= 0 {
- tb.avail = avail
- return 0, true
- }
- // Round up the missing tokens to the nearest multiple
- // of quantum - the tokens won't be available until
- // that tick.
- endTick := currentTick + (-avail+tb.quantum-1)/tb.quantum
- endTime := tb.startTime.Add(time.Duration(endTick) * tb.fillInterval)
- waitTime := endTime.Sub(now)
- if waitTime > maxWait {
- return 0, false
- }
- tb.avail = avail
- return waitTime, true
-}
-
-// adjust adjusts the current bucket capacity based on the current time.
-// It returns the current tick.
-func (tb *Bucket) adjust(now time.Time) (currentTick int64) {
- currentTick = int64(now.Sub(tb.startTime) / tb.fillInterval)
-
- if tb.avail >= tb.capacity {
- return
- }
- tb.avail += (currentTick - tb.availTick) * tb.quantum
- if tb.avail > tb.capacity {
- tb.avail = tb.capacity
- }
- tb.availTick = currentTick
- return
-}