op-service: fix exponential backoff strategy in case of high number of attempts

op-service/retry/strategies.go

@@ -14,7 +14,7 @@ type Strategy interface {
 }
 
 // ExponentialStrategy performs exponential backoff. The exponential backoff
-// function is min(e.Min + (2^attempt * 1000) + randBetween(0, e.MaxJitter), e.Max)
+// function is min(e.Min + (2^attempt * second), e.Max) + randBetween(0, e.MaxJitter)
 type ExponentialStrategy struct {
 	// Min is the minimum amount of time to wait between attempts.
 	Min time.Duration
@@ -23,15 +23,24 @@ type ExponentialStrategy struct {
 	Max time.Duration
 
 	// MaxJitter is the maximum amount of random jitter to insert between attempts.
+	// Jitter is added on top of the maximum, if the maximum is reached.
 	MaxJitter time.Duration
 }
 
 func (e *ExponentialStrategy) Duration(attempt int) time.Duration {
-	var jitter time.Duration
+	var jitter time.Duration // non-negative jitter
 	if e.MaxJitter > 0 {
 		jitter = time.Duration(rand.Int63n(e.MaxJitter.Nanoseconds()))
 	}
-	dur := e.Min + time.Duration(int(math.Pow(2, float64(attempt))*1000))*time.Millisecond
+	if attempt < 0 {
+		return e.Min + jitter
+	}
+	durFloat := float64(e.Min) * float64(time.Nanosecond)
+	durFloat += math.Pow(2, float64(attempt)) * float64(time.Second)
+	dur := time.Duration(durFloat)
+	if durFloat > float64(e.Max) {
+		dur = e.Max
+	}
 	dur += jitter
 	if dur > e.Max {
 		return e.Max
@@ -42,8 +51,9 @@ func (e *ExponentialStrategy) Duration(attempt int) time.Duration {
 
 func Exponential() Strategy {
 	return &ExponentialStrategy{
-		Max:       time.Duration(10000 * time.Millisecond),
-		MaxJitter: time.Duration(250 * time.Millisecond),
+		Min:       0,
+		Max:       10 * time.Second,
+		MaxJitter: 250 * time.Millisecond,
 	}
 }
 

op-service/retry/strategies_test.go

 package retry
 
 import (
+	"math"
 	"testing"
 	"time"
 
@@ -9,13 +10,17 @@ import (
 
 func TestExponential(t *testing.T) {
 	strategy := &ExponentialStrategy{
-		Min:       3000 * time.Millisecond,
-		Max:       10000 * time.Millisecond,
+		Min:       3 * time.Second,
+		Max:       10 * time.Second,
 		MaxJitter: 0,
 	}
 
+	require.Equal(t, 3*time.Second, strategy.Duration(-1))
 	durations := []time.Duration{4, 5, 7, 10, 10}
 	for i, dur := range durations {
-		require.Equal(t, dur*time.Second, strategy.Duration(i))
+		require.Equal(t, dur*time.Second, strategy.Duration(i), "attempt %d", i)
 	}
+	require.Equal(t, 10*time.Second, strategy.Duration(100))
+	require.Equal(t, 10*time.Second, strategy.Duration(16000))
+	require.Equal(t, 10*time.Second, strategy.Duration(math.MaxInt))
 }