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/*
* ============LICENSE_START=======================================================
* ONAP
* ================================================================================
* Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.drools.pooling;
import java.util.Deque;
import java.util.LinkedList;
import org.onap.policy.drools.pooling.message.Forward;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Finite queue of events waiting to be processed once the buckets have been
* assigned.
*/
public class EventQueue {
private static final Logger logger = LoggerFactory.getLogger(EventQueue.class);
/**
* Maximum number of events allowed in the queue. When excess events are
* added, the older events are removed.
*/
private int maxEvents;
/**
* Maximum age, in milliseconds, of events in the queue. Events that are
* older than this are discarded rather than being handed off when
* {@link #poll()} is invoked.
*/
private long maxAgeMs;
/**
* The actual queue of events.
*/
private Deque<Forward> events = new LinkedList<>();
/**
*
* @param maxEvents maximum number of events to hold in the queue
* @param maxAgeMs maximum age of events in the queue
*/
public EventQueue(int maxEvents, long maxAgeMs) {
this.maxEvents = maxEvents;
this.maxAgeMs = maxAgeMs;
}
/**
*
* @return {@code true} if the queue is empty, {@code false} otherwise
*/
public boolean isEmpty() {
return events.isEmpty();
}
/**
* Clears the queue.
*/
public void clear() {
events.clear();
}
/**
*
* @return the number of elements in the queue
*/
public int size() {
return events.size();
}
/**
* Adds an item to the queue. If the queue is full, the older item is
* removed and discarded.
*
* @param event
*/
public void add(Forward event) {
if (events.size() >= maxEvents) {
logger.warn("full queue - discarded event for topic {}", event.getTopic());
events.remove();
}
events.add(event);
}
/**
* Gets the oldest, un-expired event from the queue.
*
* @return the oldest, un-expired event
*/
public Forward poll() {
long tmin = System.currentTimeMillis() - maxAgeMs;
Forward ev;
while ((ev = events.poll()) != null) {
if (!ev.isExpired(tmin)) {
break;
}
}
return ev;
}
}
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