You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
142 lines
4.1 KiB
142 lines
4.1 KiB
/*
|
|
* Minio Cloud Storage, (C) 2016, 2017 Minio, Inc.
|
|
*
|
|
* 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 cmd
|
|
|
|
import (
|
|
"math/rand"
|
|
"sync"
|
|
"time"
|
|
)
|
|
|
|
// lockedRandSource provides protected rand source, implements rand.Source interface.
|
|
type lockedRandSource struct {
|
|
lk sync.Mutex
|
|
src rand.Source
|
|
}
|
|
|
|
// Int63 returns a non-negative pseudo-random 63-bit integer as an
|
|
// int64.
|
|
func (r *lockedRandSource) Int63() (n int64) {
|
|
r.lk.Lock()
|
|
n = r.src.Int63()
|
|
r.lk.Unlock()
|
|
return
|
|
}
|
|
|
|
// Seed uses the provided seed value to initialize the generator to a
|
|
// deterministic state.
|
|
func (r *lockedRandSource) Seed(seed int64) {
|
|
r.lk.Lock()
|
|
r.src.Seed(seed)
|
|
r.lk.Unlock()
|
|
}
|
|
|
|
// MaxJitter will randomize over the full exponential backoff time
|
|
const MaxJitter = 1.0
|
|
|
|
// NoJitter disables the use of jitter for randomizing the
|
|
// exponential backoff time
|
|
const NoJitter = 0.0
|
|
|
|
// Global random source for fetching random values.
|
|
var globalRandomSource = rand.New(&lockedRandSource{
|
|
src: rand.NewSource(time.Now().UTC().UnixNano()),
|
|
})
|
|
|
|
// newRetryTimerJitter creates a timer with exponentially increasing delays
|
|
// until the maximum retry attempts are reached. - this function is a fully
|
|
// configurable version, meant for only advanced use cases. For the most part
|
|
// one should use newRetryTimerSimple and newRetryTimer.
|
|
func newRetryTimerWithJitter(unit time.Duration, cap time.Duration, jitter float64, doneCh chan struct{}) <-chan int {
|
|
attemptCh := make(chan int)
|
|
|
|
// normalize jitter to the range [0, 1.0]
|
|
if jitter < NoJitter {
|
|
jitter = NoJitter
|
|
}
|
|
if jitter > MaxJitter {
|
|
jitter = MaxJitter
|
|
}
|
|
|
|
// computes the exponential backoff duration according to
|
|
// https://www.awsarchitectureblog.com/2015/03/backoff.html
|
|
exponentialBackoffWait := func(attempt int) time.Duration {
|
|
// 1<<uint(attempt) below could overflow, so limit the value of attempt
|
|
maxAttempt := 30
|
|
if attempt > maxAttempt {
|
|
attempt = maxAttempt
|
|
}
|
|
//sleep = random_between(0, min(cap, base * 2 ** attempt))
|
|
sleep := unit * time.Duration(1<<uint(attempt))
|
|
if sleep > cap {
|
|
sleep = cap
|
|
}
|
|
if jitter != NoJitter {
|
|
sleep -= time.Duration(globalRandomSource.Float64() * float64(sleep) * jitter)
|
|
}
|
|
return sleep
|
|
}
|
|
|
|
go func() {
|
|
defer close(attemptCh)
|
|
nextBackoff := 0
|
|
// Channel used to signal after the expiry of backoff wait seconds.
|
|
var timer *time.Timer
|
|
for {
|
|
select { // Attempts starts.
|
|
case attemptCh <- nextBackoff:
|
|
nextBackoff++
|
|
case <-doneCh:
|
|
// Stop the routine.
|
|
return
|
|
}
|
|
timer = time.NewTimer(exponentialBackoffWait(nextBackoff))
|
|
// wait till next backoff time or till doneCh gets a message.
|
|
select {
|
|
case <-timer.C:
|
|
case <-doneCh:
|
|
// stop the timer and return.
|
|
timer.Stop()
|
|
return
|
|
}
|
|
|
|
}
|
|
}()
|
|
|
|
// Start reading..
|
|
return attemptCh
|
|
}
|
|
|
|
// Default retry constants.
|
|
const (
|
|
defaultRetryUnit = time.Second // 1 second.
|
|
defaultRetryCap = 30 * time.Second // 30 seconds.
|
|
)
|
|
|
|
// newRetryTimer creates a timer with exponentially increasing delays
|
|
// until the maximum retry attempts are reached. - this function provides
|
|
// resulting retry values to be of maximum jitter.
|
|
func newRetryTimer(unit time.Duration, cap time.Duration, doneCh chan struct{}) <-chan int {
|
|
return newRetryTimerWithJitter(unit, cap, MaxJitter, doneCh)
|
|
}
|
|
|
|
// newRetryTimerSimple creates a timer with exponentially increasing delays
|
|
// until the maximum retry attempts are reached. - this function is a
|
|
// simpler version with all default values.
|
|
func newRetryTimerSimple(doneCh chan struct{}) <-chan int {
|
|
return newRetryTimerWithJitter(defaultRetryUnit, defaultRetryCap, MaxJitter, doneCh)
|
|
}
|
|
|