349 lines
10 KiB
Go
349 lines
10 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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*/
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package wait
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import (
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"errors"
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"math/rand"
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"time"
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"k8s.io/apimachinery/pkg/util/runtime"
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)
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// For any test of the style:
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// ...
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// <- time.After(timeout):
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// t.Errorf("Timed out")
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// The value for timeout should effectively be "forever." Obviously we don't want our tests to truly lock up forever, but 30s
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// is long enough that it is effectively forever for the things that can slow down a run on a heavily contended machine
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// (GC, seeks, etc), but not so long as to make a developer ctrl-c a test run if they do happen to break that test.
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var ForeverTestTimeout = time.Second * 30
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// NeverStop may be passed to Until to make it never stop.
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var NeverStop <-chan struct{} = make(chan struct{})
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// Forever calls f every period for ever.
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//
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// Forever is syntactic sugar on top of Until.
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func Forever(f func(), period time.Duration) {
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Until(f, period, NeverStop)
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}
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// Until loops until stop channel is closed, running f every period.
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//
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// Until is syntactic sugar on top of JitterUntil with zero jitter factor and
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// with sliding = true (which means the timer for period starts after the f
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// completes).
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func Until(f func(), period time.Duration, stopCh <-chan struct{}) {
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JitterUntil(f, period, 0.0, true, stopCh)
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}
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// NonSlidingUntil loops until stop channel is closed, running f every
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// period.
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//
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// NonSlidingUntil is syntactic sugar on top of JitterUntil with zero jitter
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// factor, with sliding = false (meaning the timer for period starts at the same
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// time as the function starts).
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func NonSlidingUntil(f func(), period time.Duration, stopCh <-chan struct{}) {
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JitterUntil(f, period, 0.0, false, stopCh)
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}
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// JitterUntil loops until stop channel is closed, running f every period.
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//
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// If jitterFactor is positive, the period is jittered before every run of f.
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// If jitterFactor is not positive, the period is unchanged and not jittered.
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//
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// If sliding is true, the period is computed after f runs. If it is false then
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// period includes the runtime for f.
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//
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// Close stopCh to stop. f may not be invoked if stop channel is already
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// closed. Pass NeverStop to if you don't want it stop.
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func JitterUntil(f func(), period time.Duration, jitterFactor float64, sliding bool, stopCh <-chan struct{}) {
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var t *time.Timer
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var sawTimeout bool
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for {
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select {
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case <-stopCh:
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return
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default:
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}
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jitteredPeriod := period
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if jitterFactor > 0.0 {
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jitteredPeriod = Jitter(period, jitterFactor)
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}
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if !sliding {
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t = resetOrReuseTimer(t, jitteredPeriod, sawTimeout)
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}
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func() {
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defer runtime.HandleCrash()
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f()
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}()
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if sliding {
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t = resetOrReuseTimer(t, jitteredPeriod, sawTimeout)
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}
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// NOTE: b/c there is no priority selection in golang
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// it is possible for this to race, meaning we could
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// trigger t.C and stopCh, and t.C select falls through.
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// In order to mitigate we re-check stopCh at the beginning
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// of every loop to prevent extra executions of f().
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select {
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case <-stopCh:
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return
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case <-t.C:
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sawTimeout = true
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}
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}
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}
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// Jitter returns a time.Duration between duration and duration + maxFactor *
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// duration.
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//
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// This allows clients to avoid converging on periodic behavior. If maxFactor
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// is 0.0, a suggested default value will be chosen.
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func Jitter(duration time.Duration, maxFactor float64) time.Duration {
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if maxFactor <= 0.0 {
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maxFactor = 1.0
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}
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wait := duration + time.Duration(rand.Float64()*maxFactor*float64(duration))
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return wait
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}
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// ErrWaitTimeout is returned when the condition exited without success.
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var ErrWaitTimeout = errors.New("timed out waiting for the condition")
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// ConditionFunc returns true if the condition is satisfied, or an error
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// if the loop should be aborted.
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type ConditionFunc func() (done bool, err error)
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// Backoff holds parameters applied to a Backoff function.
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type Backoff struct {
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Duration time.Duration // the base duration
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Factor float64 // Duration is multiplied by factor each iteration
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Jitter float64 // The amount of jitter applied each iteration
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Steps int // Exit with error after this many steps
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}
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// ExponentialBackoff repeats a condition check with exponential backoff.
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//
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// It checks the condition up to Steps times, increasing the wait by multiplying
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// the previous duration by Factor.
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//
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// If Jitter is greater than zero, a random amount of each duration is added
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// (between duration and duration*(1+jitter)).
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//
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// If the condition never returns true, ErrWaitTimeout is returned. All other
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// errors terminate immediately.
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func ExponentialBackoff(backoff Backoff, condition ConditionFunc) error {
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duration := backoff.Duration
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for i := 0; i < backoff.Steps; i++ {
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if i != 0 {
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adjusted := duration
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if backoff.Jitter > 0.0 {
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adjusted = Jitter(duration, backoff.Jitter)
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}
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time.Sleep(adjusted)
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duration = time.Duration(float64(duration) * backoff.Factor)
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}
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if ok, err := condition(); err != nil || ok {
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return err
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}
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}
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return ErrWaitTimeout
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}
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// Poll tries a condition func until it returns true, an error, or the timeout
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// is reached.
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//
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// Poll always waits the interval before the run of 'condition'.
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// 'condition' will always be invoked at least once.
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//
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// Some intervals may be missed if the condition takes too long or the time
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// window is too short.
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//
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// If you want to Poll something forever, see PollInfinite.
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func Poll(interval, timeout time.Duration, condition ConditionFunc) error {
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return pollInternal(poller(interval, timeout), condition)
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}
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func pollInternal(wait WaitFunc, condition ConditionFunc) error {
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done := make(chan struct{})
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defer close(done)
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return WaitFor(wait, condition, done)
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}
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// PollImmediate tries a condition func until it returns true, an error, or the timeout
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// is reached.
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//
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// Poll always checks 'condition' before waiting for the interval. 'condition'
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// will always be invoked at least once.
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//
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// Some intervals may be missed if the condition takes too long or the time
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// window is too short.
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//
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// If you want to Poll something forever, see PollInfinite.
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func PollImmediate(interval, timeout time.Duration, condition ConditionFunc) error {
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return pollImmediateInternal(poller(interval, timeout), condition)
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}
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func pollImmediateInternal(wait WaitFunc, condition ConditionFunc) error {
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done, err := condition()
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if err != nil {
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return err
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}
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if done {
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return nil
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}
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return pollInternal(wait, condition)
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}
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// PollInfinite tries a condition func until it returns true or an error
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//
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// PollInfinite always waits the interval before the run of 'condition'.
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//
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// Some intervals may be missed if the condition takes too long or the time
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// window is too short.
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func PollInfinite(interval time.Duration, condition ConditionFunc) error {
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done := make(chan struct{})
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defer close(done)
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return PollUntil(interval, condition, done)
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}
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// PollImmediateInfinite tries a condition func until it returns true or an error
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//
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// PollImmediateInfinite runs the 'condition' before waiting for the interval.
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//
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// Some intervals may be missed if the condition takes too long or the time
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// window is too short.
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func PollImmediateInfinite(interval time.Duration, condition ConditionFunc) error {
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done, err := condition()
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if err != nil {
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return err
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}
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if done {
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return nil
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}
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return PollInfinite(interval, condition)
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}
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// PollUntil tries a condition func until it returns true, an error or stopCh is
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// closed.
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//
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// PolUntil always waits interval before the first run of 'condition'.
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// 'condition' will always be invoked at least once.
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func PollUntil(interval time.Duration, condition ConditionFunc, stopCh <-chan struct{}) error {
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return WaitFor(poller(interval, 0), condition, stopCh)
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}
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// WaitFunc creates a channel that receives an item every time a test
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// should be executed and is closed when the last test should be invoked.
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type WaitFunc func(done <-chan struct{}) <-chan struct{}
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// WaitFor continually checks 'fn' as driven by 'wait'.
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//
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// WaitFor gets a channel from 'wait()'', and then invokes 'fn' once for every value
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// placed on the channel and once more when the channel is closed.
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//
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// If 'fn' returns an error the loop ends and that error is returned, and if
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// 'fn' returns true the loop ends and nil is returned.
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//
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// ErrWaitTimeout will be returned if the channel is closed without fn ever
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// returning true.
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func WaitFor(wait WaitFunc, fn ConditionFunc, done <-chan struct{}) error {
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c := wait(done)
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for {
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_, open := <-c
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ok, err := fn()
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if err != nil {
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return err
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}
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if ok {
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return nil
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}
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if !open {
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break
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}
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}
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return ErrWaitTimeout
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}
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// poller returns a WaitFunc that will send to the channel every interval until
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// timeout has elapsed and then closes the channel.
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//
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// Over very short intervals you may receive no ticks before the channel is
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// closed. A timeout of 0 is interpreted as an infinity.
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//
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// Output ticks are not buffered. If the channel is not ready to receive an
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// item, the tick is skipped.
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func poller(interval, timeout time.Duration) WaitFunc {
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return WaitFunc(func(done <-chan struct{}) <-chan struct{} {
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ch := make(chan struct{})
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go func() {
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defer close(ch)
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tick := time.NewTicker(interval)
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defer tick.Stop()
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var after <-chan time.Time
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if timeout != 0 {
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// time.After is more convenient, but it
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// potentially leaves timers around much longer
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// than necessary if we exit early.
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timer := time.NewTimer(timeout)
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after = timer.C
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defer timer.Stop()
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}
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for {
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select {
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case <-tick.C:
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// If the consumer isn't ready for this signal drop it and
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// check the other channels.
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select {
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case ch <- struct{}{}:
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default:
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}
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case <-after:
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return
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case <-done:
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return
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}
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}
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}()
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return ch
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})
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}
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// resetOrReuseTimer avoids allocating a new timer if one is already in use.
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// Not safe for multiple threads.
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func resetOrReuseTimer(t *time.Timer, d time.Duration, sawTimeout bool) *time.Timer {
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if t == nil {
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return time.NewTimer(d)
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}
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if !t.Stop() && !sawTimeout {
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<-t.C
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}
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t.Reset(d)
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return t
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}
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