PLT-3753 Added Segment analytics (#3972)

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

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+Backo [![GoDoc](http://godoc.org/github.com/segmentio/backo-go?status.png)](http://godoc.org/github.com/segmentio/backo-go)
+-----
+
+Exponential backoff for Go (Go port of segmentio/backo).
+
+
+Usage
+-----
+
+```go
+import "github.com/segmentio/backo-go"
+
+// Create a Backo instance.
+backo := backo.NewBacko(milliseconds(100), 2, 1, milliseconds(10*1000))
+// OR with defaults.
+backo := backo.DefaultBacko()
+
+// Use the ticker API.
+ticker := b.NewTicker()
+for {
+    timeout := time.After(5 * time.Minute)
+    select {
+    case  <-ticker.C:
+        fmt.Println("ticked")
+    case <- timeout:
+        fmt.Println("timed out")
+    }
+}
+
+// Or simply work with backoff intervals directly.
+for i := 0; i < n; i++ {
+    // Sleep the current goroutine.
+    backo.Sleep(i)
+    // Retrieve the duration manually.
+    duration := backo.Duration(i)
+}
+```
+
+License
+-------
+
+```
+WWWWWW||WWWWWW
+ W W W||W W W
+      ||
+    ( OO )__________
+     /  |           \
+    /o o|    MIT     \
+    \___/||_||__||_|| *
+         || ||  || ||
+        _||_|| _||_||
+       (__|__|(__|__|
+
+The MIT License (MIT)
+
+Copyright (c) 2015 Segment, 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.
+```
+
+
+
+ [1]: http://github.com/segmentio/backo-java
+ [2]: http://repository.sonatype.org/service/local/artifact/maven/redirect?r=central-proxy&g=com.segment.backo&a=backo&v=LATEST

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

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+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{}{}
+}

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

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+package backo
+
+import (
+	"fmt"
+	"math"
+	"testing"
+	"time"
+
+	"github.com/bmizerany/assert"
+)
+
+// Tests default backo behaviour.
+func TestDefaults(t *testing.T) {
+	backo := DefaultBacko()
+
+	assert.Equal(t, milliseconds(100), backo.Duration(0))
+	assert.Equal(t, milliseconds(200), backo.Duration(1))
+	assert.Equal(t, milliseconds(400), backo.Duration(2))
+	assert.Equal(t, milliseconds(800), backo.Duration(3))
+}
+
+// Tests backo does not exceed cap.
+func TestCap(t *testing.T) {
+	backo := NewBacko(milliseconds(100), 2, 0, milliseconds(600))
+
+	assert.Equal(t, milliseconds(100), backo.Duration(0))
+	assert.Equal(t, milliseconds(200), backo.Duration(1))
+	assert.Equal(t, milliseconds(400), backo.Duration(2))
+	assert.Equal(t, milliseconds(600), backo.Duration(3))
+}
+
+// Tests that jitter adds randomness.
+func TestJitter(t *testing.T) {
+	defaultBacko := NewBacko(milliseconds(100), 2, 1, milliseconds(10*1000))
+	jitterBacko := NewBacko(milliseconds(100), 2, 1, milliseconds(10*1000))
+
+	// TODO: Check jittered durations are within a range.
+	assert.NotEqual(t, jitterBacko.Duration(0), defaultBacko.Duration(0))
+	assert.NotEqual(t, jitterBacko.Duration(1), defaultBacko.Duration(1))
+	assert.NotEqual(t, jitterBacko.Duration(2), defaultBacko.Duration(2))
+	assert.NotEqual(t, jitterBacko.Duration(3), defaultBacko.Duration(3))
+}
+
+func ExampleBacko_BackoffDefault() {
+	b := DefaultBacko()
+	ticker := b.NewTicker()
+
+	for i := 0; i < 6; i++ {
+		start := time.Now()
+		select {
+		case t := <-ticker.C:
+			fmt.Println(nearest10Millis(t.Sub(start)))
+		}
+	}
+
+	ticker.Stop()
+
+	// Output:
+	// 100
+	// 200
+	// 400
+	// 800
+	// 1600
+	// 3200
+}
+
+func nearest10Millis(d time.Duration) float64 {
+	// Typically d is something like 11 or 21, so do some magic to round the
+	// durations to the nearest 10. We divide d by 10, floor it, and multiply it
+	// by 10 again.
+	return math.Floor(float64(d/time.Millisecond/10) * 10)
+}
+
+// Returns the given milliseconds as time.Duration
+func milliseconds(ms int64) time.Duration {
+	return time.Duration(ms * 1000 * 1000)
+}