54 lines
1.6 KiB
Go
54 lines
1.6 KiB
Go
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// Copyright 2017 CoreOS, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package client
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import (
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"math/rand"
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"time"
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)
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func init() {
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// Ensure seeding the prng is never forgotten, that would defeat
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// the whole point of using fuzzy timers to guard against a DoS.
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rand.Seed(time.Now().UnixNano())
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}
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// FuzzyDuration randomizes the duration d within the range specified
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// by fuzz. Specifically the value range is: [d-(fuzz/2), d+(fuzz/2)]
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// The result will never be negative.
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func FuzzyDuration(d, fuzz time.Duration) time.Duration {
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if fuzz < 0 {
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return d
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}
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// apply range [-fuzz/2, fuzz/2]
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d += time.Duration(rand.Int63n(int64(fuzz)+1) - (int64(fuzz) / 2))
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if d < 0 {
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return 0
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}
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return d
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}
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// FuzzyAfter waits for the fuzzy duration to elapse and then sends the
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// current time on the returned channel. See FuzzyDuration.
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func FuzzyAfter(d, fuzz time.Duration) <-chan time.Time {
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return time.After(FuzzyDuration(d, fuzz))
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}
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// FuzzySleep pauses the current goroutine for the fuzzy duration d.
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// See FuzzyDuration.
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func FuzzySleep(d, fuzz time.Duration) {
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time.Sleep(FuzzyDuration(d, fuzz))
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}
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