58 lines
1.4 KiB
Go
58 lines
1.4 KiB
Go
/*
|
|
Copyright 2017 Google Inc. All Rights Reserved.
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|
|
*/
|
|
|
|
package spanner
|
|
|
|
import (
|
|
"math/rand"
|
|
"time"
|
|
)
|
|
|
|
const (
|
|
// minBackoff is the minimum backoff used by default.
|
|
minBackoff = 1 * time.Second
|
|
// maxBackoff is the maximum backoff used by default.
|
|
maxBackoff = 32 * time.Second
|
|
// jitter is the jitter factor.
|
|
jitter = 0.4
|
|
// rate is the rate of exponential increase in the backoff.
|
|
rate = 1.3
|
|
)
|
|
|
|
var defaultBackoff = exponentialBackoff{minBackoff, maxBackoff}
|
|
|
|
type exponentialBackoff struct {
|
|
min, max time.Duration
|
|
}
|
|
|
|
// delay calculates the delay that should happen at n-th
|
|
// exponential backoff in a series.
|
|
func (b exponentialBackoff) delay(retries int) time.Duration {
|
|
min, max := float64(b.min), float64(b.max)
|
|
delay := min
|
|
for delay < max && retries > 0 {
|
|
delay *= rate
|
|
retries--
|
|
}
|
|
if delay > max {
|
|
delay = max
|
|
}
|
|
delay -= delay * jitter * rand.Float64()
|
|
if delay < min {
|
|
delay = min
|
|
}
|
|
return time.Duration(delay)
|
|
}
|