threadPool.shutdown();
    threadPool.awaitTermination(300, SECONDS);

    // Since we're not doing any more cache operations, and the cache only expires/evicts when doing
    // other operations, the cache and the removal queue won't change from this point on.

    // Verify that each received removal notification was valid
    for (RemovalNotification<String, String> notification : removalListener) {

  //   so that it looks like we timed out even though we didn't. For comparison FutureTask respects
  //   completion preferably and AQS is non-deterministic (depends on where in the queue the waiter
  //   is). If we wanted to be strict about it, we could store the unpark() time in the Waiter node
  //   and we could use that to make a decision about whether or not we timed out prior to being
  //   unparked.

Fixed a situation when, sometimes, the scheduler incorrectly placed a pod in the `unschedulable` queue instead of the `backoff` queue. This happened when some plugin previously declared the pod as `unschedulable` and then in a later attempt encounters some other error. Scheduling of that pod then got delayed by up to five minutes, after which periodic flushing moved the pod back into the `active` queue. ([#120334](https://github.com/kubernetes/kubernetes/pull/120334), [@pohly](https://github.com/pohly))...

    mostRecentRebuildFailed = false
  }

  /**
   * Returns a snapshot of the entry named [key], or null if it doesn't exist is not currently
   * readable. If a value is returned, it is moved to the head of the LRU queue.
   */
  @Synchronized
  @Throws(IOException::class)
  operator fun get(key: String): Snapshot? {
    initialize()

    checkNotClosed()
    validateKey(key)

     * Most Multimap implementations use a List or Set (or even Multiset) for their values, in which
     * case Multimap equality works as expected. Users who use a Collection type that does not
     * implement equals(), such as most Queue implementations, will get the same behavior from our
     * value-collection wrappers (and from Multimap.equals) as from the underlying Collection.
     */
    @SuppressWarnings("UndefinedEquals")

 * rate limit itself.
 *
 * {@snippet :
 * class CrawlingService extends AbstractScheduledService {
 *   private Set<Uri> visited;
 *   private Queue<Uri> toCrawl;
 *   protected void startUp() throws Exception {
 *     toCrawl = readStartingUris();
 *   }
 *
 *   protected void runOneIteration() throws Exception {
 *     Uri uri = toCrawl.remove();

 *  **TunnelRequest is gone.** It specified how to connect to an HTTP proxy.
    OkHttp 2 uses the new `Request` class for this.

 *  **Dispatcher** is a new class that manages the queue of asynchronous calls. It
    implements limits on total in-flight calls and in-flight calls per host.

#### Implementation changes

 * Support Android `TrafficStats` socket tagging.

- Sometimes, the scheduler incorrectly placed a pod in the "unschedulable" queue instead of the "backoff" queue. This happened when some plugin previously declared the pod as "unschedulable" and then in a later attempt encounters some other error. Scheduling of that pod then got delayed by up to five minutes, after which periodic flushing moved the pod back into the "active" queue. ([#120334](https://github.com/kubernetes/kubernetes/pull/120334), [@pohly](https://github.com/pohly))...

- Fixes the bug in PodTopologySpread that only happens with QHint enabled, 

- Previously, the scheduling queue didn't notice any extenders' failures, potentially resulting in missed cluster events and Pods rejected by Extenders being stuck in the unschedulable pod pool for up to 5 minutes in the worst-case scenario. Now, the scheduling queue notices extenders' failures and requeues Pods rejected by Extenders appropriately.