vendor files

vendor/k8s.io/apimachinery/pkg/util/wait/wait.go

@@ -0,0 +1,385 @@
+/*
+Copyright 2014 The Kubernetes Authors.
+
+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 wait
+
+import (
+	"context"
+	"errors"
+	"math/rand"
+	"sync"
+	"time"
+
+	"k8s.io/apimachinery/pkg/util/runtime"
+)
+
+// For any test of the style:
+//   ...
+//   <- time.After(timeout):
+//      t.Errorf("Timed out")
+// The value for timeout should effectively be "forever." Obviously we don't want our tests to truly lock up forever, but 30s
+// is long enough that it is effectively forever for the things that can slow down a run on a heavily contended machine
+// (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.
+var ForeverTestTimeout = time.Second * 30
+
+// NeverStop may be passed to Until to make it never stop.
+var NeverStop <-chan struct{} = make(chan struct{})
+
+// Group allows to start a group of goroutines and wait for their completion.
+type Group struct {
+	wg sync.WaitGroup
+}
+
+func (g *Group) Wait() {
+	g.wg.Wait()
+}
+
+// StartWithChannel starts f in a new goroutine in the group.
+// stopCh is passed to f as an argument. f should stop when stopCh is available.
+func (g *Group) StartWithChannel(stopCh <-chan struct{}, f func(stopCh <-chan struct{})) {
+	g.Start(func() {
+		f(stopCh)
+	})
+}
+
+// StartWithContext starts f in a new goroutine in the group.
+// ctx is passed to f as an argument. f should stop when ctx.Done() is available.
+func (g *Group) StartWithContext(ctx context.Context, f func(context.Context)) {
+	g.Start(func() {
+		f(ctx)
+	})
+}
+
+// Start starts f in a new goroutine in the group.
+func (g *Group) Start(f func()) {
+	g.wg.Add(1)
+	go func() {
+		defer g.wg.Done()
+		f()
+	}()
+}
+
+// Forever calls f every period for ever.
+//
+// Forever is syntactic sugar on top of Until.
+func Forever(f func(), period time.Duration) {
+	Until(f, period, NeverStop)
+}
+
+// Until loops until stop channel is closed, running f every period.
+//
+// Until is syntactic sugar on top of JitterUntil with zero jitter factor and
+// with sliding = true (which means the timer for period starts after the f
+// completes).
+func Until(f func(), period time.Duration, stopCh <-chan struct{}) {
+	JitterUntil(f, period, 0.0, true, stopCh)
+}
+
+// NonSlidingUntil loops until stop channel is closed, running f every
+// period.
+//
+// NonSlidingUntil is syntactic sugar on top of JitterUntil with zero jitter
+// factor, with sliding = false (meaning the timer for period starts at the same
+// time as the function starts).
+func NonSlidingUntil(f func(), period time.Duration, stopCh <-chan struct{}) {
+	JitterUntil(f, period, 0.0, false, stopCh)
+}
+
+// JitterUntil loops until stop channel is closed, running f every period.
+//
+// If jitterFactor is positive, the period is jittered before every run of f.
+// If jitterFactor is not positive, the period is unchanged and not jittered.
+//
+// If sliding is true, the period is computed after f runs. If it is false then
+// period includes the runtime for f.
+//
+// Close stopCh to stop. f may not be invoked if stop channel is already
+// closed. Pass NeverStop to if you don't want it stop.
+func JitterUntil(f func(), period time.Duration, jitterFactor float64, sliding bool, stopCh <-chan struct{}) {
+	var t *time.Timer
+	var sawTimeout bool
+
+	for {
+		select {
+		case <-stopCh:
+			return
+		default:
+		}
+
+		jitteredPeriod := period
+		if jitterFactor > 0.0 {
+			jitteredPeriod = Jitter(period, jitterFactor)
+		}
+
+		if !sliding {
+			t = resetOrReuseTimer(t, jitteredPeriod, sawTimeout)
+		}
+
+		func() {
+			defer runtime.HandleCrash()
+			f()
+		}()
+
+		if sliding {
+			t = resetOrReuseTimer(t, jitteredPeriod, sawTimeout)
+		}
+
+		// NOTE: b/c there is no priority selection in golang
+		// it is possible for this to race, meaning we could
+		// trigger t.C and stopCh, and t.C select falls through.
+		// In order to mitigate we re-check stopCh at the beginning
+		// of every loop to prevent extra executions of f().
+		select {
+		case <-stopCh:
+			return
+		case <-t.C:
+			sawTimeout = true
+		}
+	}
+}
+
+// Jitter returns a time.Duration between duration and duration + maxFactor *
+// duration.
+//
+// This allows clients to avoid converging on periodic behavior. If maxFactor
+// is 0.0, a suggested default value will be chosen.
+func Jitter(duration time.Duration, maxFactor float64) time.Duration {
+	if maxFactor <= 0.0 {
+		maxFactor = 1.0
+	}
+	wait := duration + time.Duration(rand.Float64()*maxFactor*float64(duration))
+	return wait
+}
+
+// ErrWaitTimeout is returned when the condition exited without success.
+var ErrWaitTimeout = errors.New("timed out waiting for the condition")
+
+// ConditionFunc returns true if the condition is satisfied, or an error
+// if the loop should be aborted.
+type ConditionFunc func() (done bool, err error)
+
+// Backoff holds parameters applied to a Backoff function.
+type Backoff struct {
+	Duration time.Duration // the base duration
+	Factor   float64       // Duration is multiplied by factor each iteration
+	Jitter   float64       // The amount of jitter applied each iteration
+	Steps    int           // Exit with error after this many steps
+}
+
+// ExponentialBackoff repeats a condition check with exponential backoff.
+//
+// It checks the condition up to Steps times, increasing the wait by multiplying
+// the previous duration by Factor.
+//
+// If Jitter is greater than zero, a random amount of each duration is added
+// (between duration and duration*(1+jitter)).
+//
+// If the condition never returns true, ErrWaitTimeout is returned. All other
+// errors terminate immediately.
+func ExponentialBackoff(backoff Backoff, condition ConditionFunc) error {
+	duration := backoff.Duration
+	for i := 0; i < backoff.Steps; i++ {
+		if i != 0 {
+			adjusted := duration
+			if backoff.Jitter > 0.0 {
+				adjusted = Jitter(duration, backoff.Jitter)
+			}
+			time.Sleep(adjusted)
+			duration = time.Duration(float64(duration) * backoff.Factor)
+		}
+		if ok, err := condition(); err != nil || ok {
+			return err
+		}
+	}
+	return ErrWaitTimeout
+}
+
+// Poll tries a condition func until it returns true, an error, or the timeout
+// is reached.
+//
+// Poll always waits the interval before the run of 'condition'.
+// 'condition' will always be invoked at least once.
+//
+// Some intervals may be missed if the condition takes too long or the time
+// window is too short.
+//
+// If you want to Poll something forever, see PollInfinite.
+func Poll(interval, timeout time.Duration, condition ConditionFunc) error {
+	return pollInternal(poller(interval, timeout), condition)
+}
+
+func pollInternal(wait WaitFunc, condition ConditionFunc) error {
+	done := make(chan struct{})
+	defer close(done)
+	return WaitFor(wait, condition, done)
+}
+
+// PollImmediate tries a condition func until it returns true, an error, or the timeout
+// is reached.
+//
+// Poll always checks 'condition' before waiting for the interval. 'condition'
+// will always be invoked at least once.
+//
+// Some intervals may be missed if the condition takes too long or the time
+// window is too short.
+//
+// If you want to Poll something forever, see PollInfinite.
+func PollImmediate(interval, timeout time.Duration, condition ConditionFunc) error {
+	return pollImmediateInternal(poller(interval, timeout), condition)
+}
+
+func pollImmediateInternal(wait WaitFunc, condition ConditionFunc) error {
+	done, err := condition()
+	if err != nil {
+		return err
+	}
+	if done {
+		return nil
+	}
+	return pollInternal(wait, condition)
+}
+
+// PollInfinite tries a condition func until it returns true or an error
+//
+// PollInfinite always waits the interval before the run of 'condition'.
+//
+// Some intervals may be missed if the condition takes too long or the time
+// window is too short.
+func PollInfinite(interval time.Duration, condition ConditionFunc) error {
+	done := make(chan struct{})
+	defer close(done)
+	return PollUntil(interval, condition, done)
+}
+
+// PollImmediateInfinite tries a condition func until it returns true or an error
+//
+// PollImmediateInfinite runs the 'condition' before waiting for the interval.
+//
+// Some intervals may be missed if the condition takes too long or the time
+// window is too short.
+func PollImmediateInfinite(interval time.Duration, condition ConditionFunc) error {
+	done, err := condition()
+	if err != nil {
+		return err
+	}
+	if done {
+		return nil
+	}
+	return PollInfinite(interval, condition)
+}
+
+// PollUntil tries a condition func until it returns true, an error or stopCh is
+// closed.
+//
+// PolUntil always waits interval before the first run of 'condition'.
+// 'condition' will always be invoked at least once.
+func PollUntil(interval time.Duration, condition ConditionFunc, stopCh <-chan struct{}) error {
+	return WaitFor(poller(interval, 0), condition, stopCh)
+}
+
+// WaitFunc creates a channel that receives an item every time a test
+// should be executed and is closed when the last test should be invoked.
+type WaitFunc func(done <-chan struct{}) <-chan struct{}
+
+// WaitFor continually checks 'fn' as driven by 'wait'.
+//
+// WaitFor gets a channel from 'wait()'', and then invokes 'fn' once for every value
+// placed on the channel and once more when the channel is closed.
+//
+// If 'fn' returns an error the loop ends and that error is returned, and if
+// 'fn' returns true the loop ends and nil is returned.
+//
+// ErrWaitTimeout will be returned if the channel is closed without fn ever
+// returning true.
+func WaitFor(wait WaitFunc, fn ConditionFunc, done <-chan struct{}) error {
+	c := wait(done)
+	for {
+		_, open := <-c
+		ok, err := fn()
+		if err != nil {
+			return err
+		}
+		if ok {
+			return nil
+		}
+		if !open {
+			break
+		}
+	}
+	return ErrWaitTimeout
+}
+
+// poller returns a WaitFunc that will send to the channel every interval until
+// timeout has elapsed and then closes the channel.
+//
+// Over very short intervals you may receive no ticks before the channel is
+// closed. A timeout of 0 is interpreted as an infinity.
+//
+// Output ticks are not buffered. If the channel is not ready to receive an
+// item, the tick is skipped.
+func poller(interval, timeout time.Duration) WaitFunc {
+	return WaitFunc(func(done <-chan struct{}) <-chan struct{} {
+		ch := make(chan struct{})
+
+		go func() {
+			defer close(ch)
+
+			tick := time.NewTicker(interval)
+			defer tick.Stop()
+
+			var after <-chan time.Time
+			if timeout != 0 {
+				// time.After is more convenient, but it
+				// potentially leaves timers around much longer
+				// than necessary if we exit early.
+				timer := time.NewTimer(timeout)
+				after = timer.C
+				defer timer.Stop()
+			}
+
+			for {
+				select {
+				case <-tick.C:
+					// If the consumer isn't ready for this signal drop it and
+					// check the other channels.
+					select {
+					case ch <- struct{}{}:
+					default:
+					}
+				case <-after:
+					return
+				case <-done:
+					return
+				}
+			}
+		}()
+
+		return ch
+	})
+}
+
+// resetOrReuseTimer avoids allocating a new timer if one is already in use.
+// Not safe for multiple threads.
+func resetOrReuseTimer(t *time.Timer, d time.Duration, sawTimeout bool) *time.Timer {
+	if t == nil {
+		return time.NewTimer(d)
+	}
+	if !t.Stop() && !sawTimeout {
+		<-t.C
+	}
+	t.Reset(d)
+	return t
+}