package com.netflix.eventbus.spi;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.atomic.AtomicReference;
/**
* A special subscriber that receives all events published to {@link EventBus}. This is always registered with eventbus
* but is disabled. In order to enable this subscriber call
* {@link com.netflix.eventbus.spi.EventBus#enableCatchAllSubscriber(java.util.concurrent.BlockingQueue)}
* with the sink (receiver) for all events. <br/>
* This subscriber will only call {@link java.util.concurrent.BlockingQueue#offer(Object)} on this sink to avoid any sort
* of blocking. Any events for which the offer call fails are rejected. <br/>
* As any other {@link EventBus} subscriber, this subscriber is async i.e. any events received by this subscriber are
* pushed by the eventbus in async mode. The queue size for this is {@link CatchAllSubscriber#SUBSCRIBER_QUEUE_SIZE} and
* there is no batching done for events to reduce memory overheads.
*
* @author Nitesh Kant (nkant@netflix.com)
*/
public final class CatchAllSubscriber {
private static final Logger LOGGER = LoggerFactory.getLogger(CatchAllSubscriber.class);
public static final int SUBSCRIBER_QUEUE_SIZE = 100;
private AtomicReference<BlockingQueue> sink = new AtomicReference<BlockingQueue>(null);
@Subscribe(queueSize = SUBSCRIBER_QUEUE_SIZE)
@SuppressWarnings({"unchecked", "unused"})
public void receive(Object event) {
BlockingQueue sinkNow = this.sink.get();
if (null != sinkNow && !sinkNow.offer(event)) {
LOGGER.info("CatchAllSubscriber sink full, rejected an event.");
}
}
public boolean enable(BlockingQueue sink) {
return this.sink.compareAndSet(null, sink);
}
public void disable() {
this.sink.set(null);
}
public boolean isEnabled() {
return this.sink.get() != null;
}
}