Vendor main dependencies.

vendor/github.com/cenk/backoff/LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2014 Cenk Altı
+
+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.

vendor/github.com/cenk/backoff/backoff.go

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+// Package backoff implements backoff algorithms for retrying operations.
+//
+// Use Retry function for retrying operations that may fail.
+// If Retry does not meet your needs,
+// copy/paste the function into your project and modify as you wish.
+//
+// There is also Ticker type similar to time.Ticker.
+// You can use it if you need to work with channels.
+//
+// See Examples section below for usage examples.
+package backoff
+
+import "time"
+
+// BackOff is a backoff policy for retrying an operation.
+type BackOff interface {
+	// NextBackOff returns the duration to wait before retrying the operation,
+	// or backoff.Stop to indicate that no more retries should be made.
+	//
+	// Example usage:
+	//
+	// 	duration := backoff.NextBackOff();
+	// 	if (duration == backoff.Stop) {
+	// 		// Do not retry operation.
+	// 	} else {
+	// 		// Sleep for duration and retry operation.
+	// 	}
+	//
+	NextBackOff() time.Duration
+
+	// Reset to initial state.
+	Reset()
+}
+
+// Stop indicates that no more retries should be made for use in NextBackOff().
+const Stop time.Duration = -1
+
+// ZeroBackOff is a fixed backoff policy whose backoff time is always zero,
+// meaning that the operation is retried immediately without waiting, indefinitely.
+type ZeroBackOff struct{}
+
+func (b *ZeroBackOff) Reset() {}
+
+func (b *ZeroBackOff) NextBackOff() time.Duration { return 0 }
+
+// StopBackOff is a fixed backoff policy that always returns backoff.Stop for
+// NextBackOff(), meaning that the operation should never be retried.
+type StopBackOff struct{}
+
+func (b *StopBackOff) Reset() {}
+
+func (b *StopBackOff) NextBackOff() time.Duration { return Stop }
+
+// ConstantBackOff is a backoff policy that always returns the same backoff delay.
+// This is in contrast to an exponential backoff policy,
+// which returns a delay that grows longer as you call NextBackOff() over and over again.
+type ConstantBackOff struct {
+	Interval time.Duration
+}
+
+func (b *ConstantBackOff) Reset()                     {}
+func (b *ConstantBackOff) NextBackOff() time.Duration { return b.Interval }
+
+func NewConstantBackOff(d time.Duration) *ConstantBackOff {
+	return &ConstantBackOff{Interval: d}
+}

vendor/github.com/cenk/backoff/exponential.go

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+package backoff
+
+import (
+	"math/rand"
+	"time"
+)
+
+/*
+ExponentialBackOff is a backoff implementation that increases the backoff
+period for each retry attempt using a randomization function that grows exponentially.
+
+NextBackOff() is calculated using the following formula:
+
+ randomized interval =
+     RetryInterval * (random value in range [1 - RandomizationFactor, 1 + RandomizationFactor])
+
+In other words NextBackOff() will range between the randomization factor
+percentage below and above the retry interval.
+
+For example, given the following parameters:
+
+ RetryInterval = 2
+ RandomizationFactor = 0.5
+ Multiplier = 2
+
+the actual backoff period used in the next retry attempt will range between 1 and 3 seconds,
+multiplied by the exponential, that is, between 2 and 6 seconds.
+
+Note: MaxInterval caps the RetryInterval and not the randomized interval.
+
+If the time elapsed since an ExponentialBackOff instance is created goes past the
+MaxElapsedTime, then the method NextBackOff() starts returning backoff.Stop.
+
+The elapsed time can be reset by calling Reset().
+
+Example: Given the following default arguments, for 10 tries the sequence will be,
+and assuming we go over the MaxElapsedTime on the 10th try:
+
+ Request #  RetryInterval (seconds)  Randomized Interval (seconds)
+
+  1          0.5                     [0.25,   0.75]
+  2          0.75                    [0.375,  1.125]
+  3          1.125                   [0.562,  1.687]
+  4          1.687                   [0.8435, 2.53]
+  5          2.53                    [1.265,  3.795]
+  6          3.795                   [1.897,  5.692]
+  7          5.692                   [2.846,  8.538]
+  8          8.538                   [4.269, 12.807]
+  9         12.807                   [6.403, 19.210]
+ 10         19.210                   backoff.Stop
+
+Note: Implementation is not thread-safe.
+*/
+type ExponentialBackOff struct {
+	InitialInterval     time.Duration
+	RandomizationFactor float64
+	Multiplier          float64
+	MaxInterval         time.Duration
+	// After MaxElapsedTime the ExponentialBackOff stops.
+	// It never stops if MaxElapsedTime == 0.
+	MaxElapsedTime time.Duration
+	Clock          Clock
+
+	currentInterval time.Duration
+	startTime       time.Time
+}
+
+// Clock is an interface that returns current time for BackOff.
+type Clock interface {
+	Now() time.Time
+}
+
+// Default values for ExponentialBackOff.
+const (
+	DefaultInitialInterval     = 500 * time.Millisecond
+	DefaultRandomizationFactor = 0.5
+	DefaultMultiplier          = 1.5
+	DefaultMaxInterval         = 60 * time.Second
+	DefaultMaxElapsedTime      = 15 * time.Minute
+)
+
+// NewExponentialBackOff creates an instance of ExponentialBackOff using default values.
+func NewExponentialBackOff() *ExponentialBackOff {
+	b := &ExponentialBackOff{
+		InitialInterval:     DefaultInitialInterval,
+		RandomizationFactor: DefaultRandomizationFactor,
+		Multiplier:          DefaultMultiplier,
+		MaxInterval:         DefaultMaxInterval,
+		MaxElapsedTime:      DefaultMaxElapsedTime,
+		Clock:               SystemClock,
+	}
+	if b.RandomizationFactor < 0 {
+		b.RandomizationFactor = 0
+	} else if b.RandomizationFactor > 1 {
+		b.RandomizationFactor = 1
+	}
+	b.Reset()
+	return b
+}
+
+type systemClock struct{}
+
+func (t systemClock) Now() time.Time {
+	return time.Now()
+}
+
+// SystemClock implements Clock interface that uses time.Now().
+var SystemClock = systemClock{}
+
+// Reset the interval back to the initial retry interval and restarts the timer.
+func (b *ExponentialBackOff) Reset() {
+	b.currentInterval = b.InitialInterval
+	b.startTime = b.Clock.Now()
+}
+
+// NextBackOff calculates the next backoff interval using the formula:
+// 	Randomized interval = RetryInterval +/- (RandomizationFactor * RetryInterval)
+func (b *ExponentialBackOff) NextBackOff() time.Duration {
+	// Make sure we have not gone over the maximum elapsed time.
+	if b.MaxElapsedTime != 0 && b.GetElapsedTime() > b.MaxElapsedTime {
+		return Stop
+	}
+	defer b.incrementCurrentInterval()
+	return getRandomValueFromInterval(b.RandomizationFactor, rand.Float64(), b.currentInterval)
+}
+
+// GetElapsedTime returns the elapsed time since an ExponentialBackOff instance
+// is created and is reset when Reset() is called.
+//
+// The elapsed time is computed using time.Now().UnixNano().
+func (b *ExponentialBackOff) GetElapsedTime() time.Duration {
+	return b.Clock.Now().Sub(b.startTime)
+}
+
+// Increments the current interval by multiplying it with the multiplier.
+func (b *ExponentialBackOff) incrementCurrentInterval() {
+	// Check for overflow, if overflow is detected set the current interval to the max interval.
+	if float64(b.currentInterval) >= float64(b.MaxInterval)/b.Multiplier {
+		b.currentInterval = b.MaxInterval
+	} else {
+		b.currentInterval = time.Duration(float64(b.currentInterval) * b.Multiplier)
+	}
+}
+
+// Returns a random value from the following interval:
+// 	[randomizationFactor * currentInterval, randomizationFactor * currentInterval].
+func getRandomValueFromInterval(randomizationFactor, random float64, currentInterval time.Duration) time.Duration {
+	var delta = randomizationFactor * float64(currentInterval)
+	var minInterval = float64(currentInterval) - delta
+	var maxInterval = float64(currentInterval) + delta
+
+	// Get a random value from the range [minInterval, maxInterval].
+	// The formula used below has a +1 because if the minInterval is 1 and the maxInterval is 3 then
+	// we want a 33% chance for selecting either 1, 2 or 3.
+	return time.Duration(minInterval + (random * (maxInterval - minInterval + 1)))
+}

vendor/github.com/cenk/backoff/retry.go

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+package backoff
+
+import "time"
+
+// An Operation is executing by Retry() or RetryNotify().
+// The operation will be retried using a backoff policy if it returns an error.
+type Operation func() error
+
+// Notify is a notify-on-error function. It receives an operation error and
+// backoff delay if the operation failed (with an error).
+//
+// NOTE that if the backoff policy stated to stop retrying,
+// the notify function isn't called.
+type Notify func(error, time.Duration)
+
+// Retry the operation o until it does not return error or BackOff stops.
+// o is guaranteed to be run at least once.
+// It is the caller's responsibility to reset b after Retry returns.
+//
+// Retry sleeps the goroutine for the duration returned by BackOff after a
+// failed operation returns.
+func Retry(o Operation, b BackOff) error { return RetryNotify(o, b, nil) }
+
+// RetryNotify calls notify function with the error and wait duration
+// for each failed attempt before sleep.
+func RetryNotify(operation Operation, b BackOff, notify Notify) error {
+	var err error
+	var next time.Duration
+
+	b.Reset()
+	for {
+		if err = operation(); err == nil {
+			return nil
+		}
+
+		if next = b.NextBackOff(); next == Stop {
+			return err
+		}
+
+		if notify != nil {
+			notify(err, next)
+		}
+
+		time.Sleep(next)
+	}
+}

vendor/github.com/cenk/backoff/ticker.go

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+package backoff
+
+import (
+	"runtime"
+	"sync"
+	"time"
+)
+
+// Ticker holds a channel that delivers `ticks' of a clock at times reported by a BackOff.
+//
+// Ticks will continue to arrive when the previous operation is still running,
+// so operations that take a while to fail could run in quick succession.
+type Ticker struct {
+	C        <-chan time.Time
+	c        chan time.Time
+	b        BackOff
+	stop     chan struct{}
+	stopOnce sync.Once
+}
+
+// NewTicker returns a new Ticker containing a channel that will send the time at times
+// specified by the BackOff argument. Ticker is guaranteed to tick at least once.
+// The channel is closed when Stop method is called or BackOff stops.
+func NewTicker(b BackOff) *Ticker {
+	c := make(chan time.Time)
+	t := &Ticker{
+		C:    c,
+		c:    c,
+		b:    b,
+		stop: make(chan struct{}),
+	}
+	go t.run()
+	runtime.SetFinalizer(t, (*Ticker).Stop)
+	return t
+}
+
+// Stop turns off a ticker. After Stop, no more ticks will be sent.
+func (t *Ticker) Stop() {
+	t.stopOnce.Do(func() { close(t.stop) })
+}
+
+func (t *Ticker) run() {
+	c := t.c
+	defer close(c)
+	t.b.Reset()
+
+	// Ticker is guaranteed to tick at least once.
+	afterC := t.send(time.Now())
+
+	for {
+		if afterC == nil {
+			return
+		}
+
+		select {
+		case tick := <-afterC:
+			afterC = t.send(tick)
+		case <-t.stop:
+			t.c = nil // Prevent future ticks from being sent to the channel.
+			return
+		}
+	}
+}
+
+func (t *Ticker) send(tick time.Time) <-chan time.Time {
+	select {
+	case t.c <- tick:
+	case <-t.stop:
+		return nil
+	}
+
+	next := t.b.NextBackOff()
+	if next == Stop {
+		t.Stop()
+		return nil
+	}
+
+	return time.After(next)
+}