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Fix exponential backoff algorithm truncating exponential factor #14

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Fix exponential backoff algorithm truncating exponential factor #14

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2 changes: 1 addition & 1 deletion backoff/backoff.go
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ func Linear(factor time.Duration) Algorithm {
// calculated as the given base raised to the attempt number.
func Exponential(factor time.Duration, base float64) Algorithm {
return func(attempt uint) time.Duration {
return (factor * time.Duration(math.Pow(base, float64(attempt))))
return time.Duration(float64(factor) * math.Pow(base, float64(attempt)))
}
}

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16 changes: 8 additions & 8 deletions backoff/backoff_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -40,13 +40,13 @@ func TestLinear(t *testing.T) {

func TestExponential(t *testing.T) {
const duration = time.Second
const base = 3
const base = 1.5

algorithm := Exponential(duration, base)

for i := uint(0); i < 10; i++ {
result := algorithm(i)
expected := time.Duration(math.Pow(base, float64(i))) * duration
expected := time.Duration(math.Pow(base, float64(i)) * float64(duration))

if result != expected {
t.Errorf("algorithm expected to return a %s duration, but received %s instead", expected, result)
Expand Down Expand Up @@ -132,7 +132,7 @@ func ExampleLinear() {
}

func ExampleExponential() {
algorithm := Exponential(15*time.Millisecond, 3)
algorithm := Exponential(15*time.Millisecond, 1.5)

for i := uint(1); i <= 5; i++ {
duration := algorithm(i)
Expand All @@ -141,11 +141,11 @@ func ExampleExponential() {
}

// Output:
// #1 attempt: 45ms
// #2 attempt: 135ms
// #3 attempt: 405ms
// #4 attempt: 1.215s
// #5 attempt: 3.645s
// #1 attempt: 22.5ms
// #2 attempt: 33.75ms
// #3 attempt: 50.625ms
// #4 attempt: 75.9375ms
// #5 attempt: 113.90625ms
}

func ExampleBinaryExponential() {
Expand Down