PLT-3753 Added Segment analytics (#3972)

vendor/github.com/segmentio/backo-go/backo.go

@@ -0,0 +1,83 @@
+package backo
+
+import (
+	"math"
+	"math/rand"
+	"time"
+)
+
+type Backo struct {
+	base   time.Duration
+	factor uint8
+	jitter float64
+	cap    time.Duration
+}
+
+// Creates a backo instance with the given parameters
+func NewBacko(base time.Duration, factor uint8, jitter float64, cap time.Duration) *Backo {
+	return &Backo{base, factor, jitter, cap}
+}
+
+// Creates a backo instance with the following defaults:
+//   base: 100 milliseconds
+//   factor: 2
+//   jitter: 0
+//   cap: 10 seconds
+func DefaultBacko() *Backo {
+	return NewBacko(time.Millisecond*100, 2, 0, time.Second*10)
+}
+
+// Duration returns the backoff interval for the given attempt.
+func (backo *Backo) Duration(attempt int) time.Duration {
+	duration := float64(backo.base) * math.Pow(float64(backo.factor), float64(attempt))
+
+	if backo.jitter != 0 {
+		random := rand.Float64()
+		deviation := math.Floor(random * backo.jitter * duration)
+		if (int(math.Floor(random*10)) & 1) == 0 {
+			duration = duration - deviation
+		} else {
+			duration = duration + deviation
+		}
+	}
+
+	duration = math.Min(float64(duration), float64(backo.cap))
+	return time.Duration(duration)
+}
+
+// Sleep pauses the current goroutine for the backoff interval for the given attempt.
+func (backo *Backo) Sleep(attempt int) {
+	duration := backo.Duration(attempt)
+	time.Sleep(duration)
+}
+
+type Ticker struct {
+	done chan struct{}
+	C    <-chan time.Time
+}
+
+func (b *Backo) NewTicker() *Ticker {
+	c := make(chan time.Time, 1)
+	ticker := &Ticker{
+		done: make(chan struct{}, 1),
+		C:    c,
+	}
+
+	go func() {
+		for i := 0; ; i++ {
+			select {
+			case t := <-time.After(b.Duration(i)):
+				c <- t
+			case <-ticker.done:
+				close(c)
+				return
+			}
+		}
+	}()
+
+	return ticker
+}
+
+func (t *Ticker) Stop() {
+	t.done <- struct{}{}
+}