add exponential backoff as retry logic

common/retry/retry.go

@@ -16,34 +16,43 @@ type Strategy interface {
 }
 
 type retryer struct {
-	NextDelay func(int) int
+	totalAttempt int
+	nextDelay    func() uint32
 }
 
 // On implements Strategy.On.
 func (r *retryer) On(method func() error) error {
 	attempt := 0
-	for {
+	for attempt < r.totalAttempt {
 		err := method()
 		if err == nil {
 			return nil
 		}
-		delay := r.NextDelay(attempt)
-		if delay < 0 {
-			return ErrRetryFailed
-		}
+		delay := r.nextDelay()
 		<-time.After(time.Duration(delay) * time.Millisecond)
 		attempt++
 	}
+	return ErrRetryFailed
 }
 
 // Timed returns a retry strategy with fixed interval.
-func Timed(attempts int, delay int) Strategy {
+func Timed(attempts int, delay uint32) Strategy {
 	return &retryer{
-		NextDelay: func(attempt int) int {
-			if attempt >= attempts {
-				return -1
-			}
+		totalAttempt: attempts,
+		nextDelay: func() uint32 {
 			return delay
 		},
 	}
 }
+
+func ExponentialBackoff(attempts int, delay uint32) Strategy {
+	nextDelay := uint32(0)
+	return &retryer{
+		totalAttempt: attempts,
+		nextDelay: func() uint32 {
+			r := nextDelay
+			nextDelay += delay
+			return r
+		},
+	}
+}