- apiserver_flowcontrol_current_r: R(the time of the last change in state of the queues)
  - apiserver_flowcontrol_dispatch_r: R(the time of the latest request dispatch)
  - apiserver_flowcontrol_latest_s: S(the request last dispatched) = R(when that request starts executing in the virtual world)
  - apiserver_flowcontrol_next_s_bounds: min and max next S among non-empty queues

    /** Runnable is not running and not queued for execution */
    IDLE,
    /** Runnable is not running, but is being queued for execution */
    QUEUING,
    /** runnable has been submitted but has not yet begun execution */
    QUEUED,
    RUNNING,
  }

  /** Underlying executor that all submitted Runnable objects are run on. */
  private final Executor executor;

  @GuardedBy("queue")

    /**
     * Used to update and read the latestTaskQueue field. Set to null once the runnable has been run
     * or queued.
     */
    @Nullable ExecutionSequencer sequencer;

    /**
     * Executor the task was set to run on. Set to null when the task has been queued, run, or
     * cancelled.
     */
    @Nullable Executor delegate;

    /**

   * formally, removes an element {@code e} such that {@code o.equals(e)}, if this queue contains
   * one or more such elements. Returns {@code true} if and only if this queue contained the
   * specified element (or equivalently, if this queue changed as a result of the call).
   *
   * @param o element to be removed from this queue, if present

- Scheduler: added metrics to record the number of pending pods in different queues ([#75501](https://github.com/kubernetes/kubernetes/pull/75501), [@Huang-Wei](https://github.com/Huang-Wei))

      ReferenceQueue<Object> queue,
      PhantomReference<Object> frqReference) {
    this.queue = queue;

    this.finalizableReferenceClassReference = new WeakReference<>(finalizableReferenceClass);

    // Keep track of the FRQ that started us so we know when to stop.
    this.frqReference = frqReference;
  }

  /** Loops continuously, pulling references off the queue and cleaning them up. */

        return true;
    }

    /**
     * Stores child URLs from the given set into the crawling queue for future processing.
     * This method filters out blank URLs and increments the depth for child URLs.
     *
     * @param urlQueue the parent URL queue item
     * @param childUrlSet the set of child URLs to be queued for crawling
     */

    checkNotNull(event, "event");
    checkNotNull(label, "label");
    synchronized (listeners) {
      for (PerListenerQueue<L> queue : listeners) {
        queue.add(event, label);
      }
    }
  }

  /**
   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *

query.additional.cache.response.fields=
# Additional highlighted fields for queries.
query.additional.highlighted.fields=
# Additional search fields for queries.
query.additional.search.fields=
# Additional facet fields for queries.
query.additional.facet.fields=
# Additional sort fields for queries.
query.additional.sort.fields=
# Additional analyzed fields for queries.
query.additional.analyzed.fields=

     */
    public QueryStringBuilder() {
        // Default constructor
    }

    /**
     * Quotes a string value if it contains spaces.
     * Multi-word values are wrapped in double quotes with internal quotes replaced by spaces.
     *
     * @param value the string value to quote
     * @return the quoted string if it contains spaces, otherwise the original value
     */