Fix exponentialBackoffer overflowing into negative

Signed-off-by: Jakub Sztandera <[email protected]>

gpbft/options.go

@@ -113,12 +113,12 @@ func WithRebroadcastBackoff(exponent float64, base, max time.Duration) Option {
 	}
 }
 
-func exponentialBackoffer(exponent float64, base, max time.Duration) func(attempt int) time.Duration {
+func exponentialBackoffer(exponent float64, base, maxBackoff time.Duration) func(attempt int) time.Duration {
 	return func(attempt int) time.Duration {
-		nextBackoff := time.Duration(float64(base) * math.Pow(exponent, float64(attempt)))
-		if nextBackoff > max {
-			return max
+		nextBackoff := float64(base) * math.Pow(exponent, float64(attempt))
+		if nextBackoff > float64(maxBackoff) {
+			return maxBackoff
 		}
-		return nextBackoff
+		return maxBackoff
 	}
 }

gpbft/options_test.go

@@ -0,0 +1,18 @@
+package gpbft
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func Test_exponentialBackoffer(t *testing.T) {
+	maxBackoff := 30 * time.Second
+	backoffer := exponentialBackoffer(1.3, 3*time.Second, maxBackoff)
+	for i := 0; i < 10_000; i++ {
+		backoff := backoffer(i)
+		require.Positivef(t, backoff, "at %d", i)
+		require.LessOrEqualf(t, backoff, maxBackoff, "at %d", i)
+	}
+}