* 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();

    }
}
```

## 9. Performance and Optimization

### 9.1 Witness Event Batching
```java
public class WitnessEventBatcher {
    private final Queue<WitnessNotification> pendingNotifications;
    private final ScheduledExecutorService scheduler;
    private final int batchSize = 10;
    private final long batchTimeout = 100;  // 100ms
    

  Now, when unschedulable Pods are updated, the scheduling queue checks with QueueingHint(s) whether the update may make the pods schedulable, and requeues them to activeQ/backoffQ **only when** at least one QueueingHint(s) return Queue. 
  
  Action required for custom scheduler plugin developers:

,"toUpperCase","camelCase","string","acceptData","owner","Data","uid","defineProperty","configurable","set","data","prop","hasData","dataPriv","dataUser","rbrace","rmultiDash","dataAttr","JSON","parse","removeData","_data","_removeData","attrs","dequeue","startLength","hooks","_queueHooks","unshift","stop","setter","clearQueue","tmp","count","defer","pnum","source","rcssNum","cssExpand","isAttached","composed","getRootNode","isHiddenWithinTree","style","display","css","adjustCSS","valueParts","t...

			}
			t.Log("Client Context canceled. err state:", err)
			clientCanceled <- time.Now()
		}(t)
		start := time.Now()
		if st.Requests != nil {
			defer close(st.Requests)
		}
		// Fill up queue.
		for sendReq {
			select {
			case st.Requests <- []byte("Hello"):
				time.Sleep(10 * time.Millisecond)
			default:
				sendReq = false
			}
		}
		cancel()
		<-serverCanceled

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

github.com/eapache/go-xerial-snappy v0.0.0-20230731223053-c322873962e3/go.mod h1:YvSRo5mw33fLEx1+DlK6L2VV43tJt5Eyel9n9XBcR+0=
github.com/eapache/queue v1.1.0 h1:YOEu7KNc61ntiQlcEeUIoDTJ2o8mQznoNvUhiigpIqc=
github.com/eapache/queue v1.1.0/go.mod h1:6eCeP0CKFpHLu8blIFXhExK/dRa7WDZfr6jVFPTqq+I=
github.com/eclipse/paho.mqtt.golang v1.5.0 h1:EH+bUVJNgttidWFkLLVKaQPGmkTUfQQqjOsyvMGvD6o=

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

### Scheduling

- Improved fairness of the scheduling queue by placing pods which are attempted recently behind other pods with the same priority. ([#73700](https://github.com/kubernetes/kubernetes/pull/73700), [@denkensk](https://github.com/denkensk))