Add WithDeadlineTimer interface to clock

[tatsuhiro-t]

What type of PR is this?
/kind feature

What this PR does / why we need it:

This is a part of effort to fix kubernetes/kubernetes#125581

WithDeadlineTimer interface extends Clock to add NewDeadlineTimer. NewDeadlineTimer is similar to NewTimer, but it returns a timer which fires at the given timestamp. It makes unit testing easier with FakeClock.Step when a test subject is making a timer inside goroutine (e.g., workqueue.NewDelayingQueue). With NewTimer, in some race conditions, a timer never fire if FakeClock.Step is called after getting the base time Now() and calling NewTimer(). This is because the duration passed to timer is calculated against the old timestamp, but inside FakeClock.NewTimer, the targetTime is calculated against the time adjusted by Step. With NewDeadlineTimer, targetTime is not adjusted, which works around this issue.

Because workqueue.DelayingQueueConfig uses clock.WithTicker and changing it breaks API compatibility, I plan to do type assertion like so to use NewDeadlineTimer if available:

diff --git a/staging/src/k8s.io/client-go/util/workqueue/delaying_queue.go b/staging/src/k8s.io/client-go/util/workqueue/delaying_queue.go
index 958b96a80c3..e3bebd36987 100644
--- a/staging/src/k8s.io/client-go/util/workqueue/delaying_queue.go
+++ b/staging/src/k8s.io/client-go/util/workqueue/delaying_queue.go
@@ -251,6 +251,14 @@ func (q *delayingType[T]) AddAfter(item T, duration time.Duration) {
        }
 }
 
+type deadlineTimerClock struct {
+       clock.Clock
+}
+
+func (c deadlineTimerClock) NewDeadlineTimer(ts time.Time) clock.Timer {
+       return c.NewTimer(ts.Sub(c.Now()))
+}
+
 // maxWait keeps a max bound on the wait time. It's just insurance against weird things happening.
 // Checking the queue every 10 seconds isn't expensive and we know that we'll never end up with an
 // expired item sitting for more than 10 seconds.
@@ -271,6 +279,11 @@ func (q *delayingType[T]) waitingLoop() {
 
        waitingEntryByData := map[t]*waitFor{}
 
+       deadlineClock, ok := q.clock.(clock.WithDeadlineTimer)
+       if !ok {
+               deadlineClock = deadlineTimerClock{Clock: q.clock}
+       }
+
        for {
                if q.TypedInterface.ShuttingDown() {
                        return
@@ -297,7 +310,7 @@ func (q *delayingType[T]) waitingLoop() {
                                nextReadyAtTimer.Stop()
                        }
                        entry := waitingForQueue.Peek().(*waitFor)
-                       nextReadyAtTimer = q.clock.NewTimer(entry.readyAt.Sub(now))
+                       nextReadyAtTimer = deadlineClock.NewDeadlineTimer(entry.readyAt)
                        nextReadyAt = nextReadyAtTimer.C()
                } 

Which issue(s) this PR fixes:

kubernetes/kubernetes#125581

Special notes for your reviewer:

Release note:

This PR adds WithDeadlineTimer interface extends Clock to add NewDeadlineTimer. NewDeadlineTimer is similar to NewTimer, but it returns a timer which fires at the given timestamp.

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@k8s-triage-robot: Closed this PR.

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/close

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[mauri870]

/reopen

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@mauri870: Reopened this PR.

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[mauri870]

/remove-lifecycle rotten

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[mauri870]

@deads2k @mengqiy Could you take a look at this when you have a chance? Thanks!