61 lines
1.8 KiB
Go
61 lines
1.8 KiB
Go
// Copyright 2018 clair authors
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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 timeutil implements extra utilities dealing with time not found
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// in the standard library.
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package timeutil
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import (
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"math"
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"math/rand"
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"time"
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log "github.com/sirupsen/logrus"
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"github.com/coreos/clair/pkg/stopper"
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)
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// ApproxSleep is a stoppable time.Sleep that adds a slight random variation to
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// the wakeup time in order to prevent thundering herds.
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func ApproxSleep(approxWakeup time.Time, st *stopper.Stopper) (stopped bool) {
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waitUntil := approxWakeup.Add(time.Duration(rand.ExpFloat64()/0.5) * time.Second)
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log.WithField("wakeup", waitUntil).Debug("updater sleeping")
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now := time.Now().UTC()
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if !waitUntil.Before(now) {
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if !st.Sleep(waitUntil.Sub(now)) {
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return true
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}
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}
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return false
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}
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// ExpBackoff doubles the backoff time, if the result is longer than the
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// parameter max, max will be returned.
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func ExpBackoff(prev, max time.Duration) time.Duration {
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t := 2 * prev
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if t > max {
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t = max
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}
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if t == 0 {
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return time.Second
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}
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return t
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}
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// FractionalDuration calculates the fraction of a Duration rounding half way
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// from zero.
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func FractionalDuration(fraction float64, d time.Duration) time.Duration {
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return time.Duration(math.Round(float64(d) * fraction))
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}
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