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68 lines
2.6 KiB
Go
68 lines
2.6 KiB
Go
// Copyright (c) 2015-2021 MinIO, Inc.
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//
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// This file is part of MinIO Object Storage stack
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package crypto
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import (
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"math/rand"
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"time"
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)
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// default retry configuration
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const (
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retryWaitMin = 100 * time.Millisecond // minimum retry limit.
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retryWaitMax = 1500 * time.Millisecond // 1.5 secs worth of max retry.
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)
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// LinearJitterBackoff provides the time.Duration for a caller to
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// perform linear backoff based on the attempt number and with jitter to
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// prevent a thundering herd.
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//
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// min and max here are *not* absolute values. The number to be multiplied by
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// the attempt number will be chosen at random from between them, thus they are
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// bounding the jitter.
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//
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// For instance:
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// * To get strictly linear backoff of one second increasing each retry, set
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// both to one second (1s, 2s, 3s, 4s, ...)
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// * To get a small amount of jitter centered around one second increasing each
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// retry, set to around one second, such as a min of 800ms and max of 1200ms
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// (892ms, 2102ms, 2945ms, 4312ms, ...)
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// * To get extreme jitter, set to a very wide spread, such as a min of 100ms
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// and a max of 20s (15382ms, 292ms, 51321ms, 35234ms, ...)
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func LinearJitterBackoff(min, max time.Duration, attemptNum int) time.Duration {
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// attemptNum always starts at zero but we want to start at 1 for multiplication
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attemptNum++
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if max <= min {
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// Unclear what to do here, or they are the same, so return min *
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// attemptNum
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return min * time.Duration(attemptNum)
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}
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// Seed rand; doing this every time is fine
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rand := rand.New(rand.NewSource(int64(time.Now().Nanosecond())))
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// Pick a random number that lies somewhere between the min and max and
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// multiply by the attemptNum. attemptNum starts at zero so we always
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// increment here. We first get a random percentage, then apply that to the
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// difference between min and max, and add to min.
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jitter := rand.Float64() * float64(max-min)
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jitterMin := int64(jitter) + int64(min)
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return time.Duration(jitterMin * int64(attemptNum))
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}
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