/* * MinIO Go Library for Amazon S3 Compatible Cloud Storage * Copyright 2015-2017 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 minio import "time" // newRetryTimerContinous creates a timer with exponentially increasing delays forever. func (c *Client) newRetryTimerContinous(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(c.random.Float64() * float64(sleep) * jitter) } return sleep } go func() { defer close(attemptCh) var nextBackoff int for { select { // Attempts starts. case attemptCh <- nextBackoff: nextBackoff++ case <-doneCh: // Stop the routine. return } time.Sleep(exponentialBackoffWait(nextBackoff)) } }() return attemptCh }