retry-continous.go (1973B)
1 /* 2 * MinIO Go Library for Amazon S3 Compatible Cloud Storage 3 * Copyright 2015-2017 MinIO, Inc. 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package minio 19 20 import "time" 21 22 // newRetryTimerContinous creates a timer with exponentially increasing delays forever. 23 func (c *Client) newRetryTimerContinous(unit time.Duration, cap time.Duration, jitter float64, doneCh chan struct{}) <-chan int { 24 attemptCh := make(chan int) 25 26 // normalize jitter to the range [0, 1.0] 27 if jitter < NoJitter { 28 jitter = NoJitter 29 } 30 if jitter > MaxJitter { 31 jitter = MaxJitter 32 } 33 34 // computes the exponential backoff duration according to 35 // https://www.awsarchitectureblog.com/2015/03/backoff.html 36 exponentialBackoffWait := func(attempt int) time.Duration { 37 // 1<<uint(attempt) below could overflow, so limit the value of attempt 38 maxAttempt := 30 39 if attempt > maxAttempt { 40 attempt = maxAttempt 41 } 42 // sleep = random_between(0, min(cap, base * 2 ** attempt)) 43 sleep := unit * time.Duration(1<<uint(attempt)) 44 if sleep > cap { 45 sleep = cap 46 } 47 if jitter != NoJitter { 48 sleep -= time.Duration(c.random.Float64() * float64(sleep) * jitter) 49 } 50 return sleep 51 } 52 53 go func() { 54 defer close(attemptCh) 55 var nextBackoff int 56 for { 57 select { 58 // Attempts starts. 59 case attemptCh <- nextBackoff: 60 nextBackoff++ 61 case <-doneCh: 62 // Stop the routine. 63 return 64 } 65 time.Sleep(exponentialBackoffWait(nextBackoff)) 66 } 67 }() 68 return attemptCh 69 }