/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package org.apache.kafka.streams.processor.internals;
import java.util.LinkedList;
/**
* MinTimestampTracker implements {@link TimestampTracker} that maintains the min
* timestamp of the maintained stamped elements.
*/
public class MinTimestampTracker<E> implements TimestampTracker<E> {
// first element has the lowest timestamp and last element the highest
private final LinkedList<Stamped<E>> ascendingSubsequence = new LinkedList<>();
// in the case that incoming traffic is very small, the records maybe put and polled
// within a single iteration, in this case we need to remember the last polled
// record's timestamp
private long lastKnownTime = NOT_KNOWN;
/**
* @throws NullPointerException if the element is null
*/
public void addElement(final Stamped<E> elem) {
if (elem == null) throw new NullPointerException();
Stamped<E> maxElem = ascendingSubsequence.peekLast();
while (maxElem != null && maxElem.timestamp >= elem.timestamp) {
ascendingSubsequence.removeLast();
maxElem = ascendingSubsequence.peekLast();
}
ascendingSubsequence.offerLast(elem); //lower timestamps have been retained and all greater/equal removed
}
public void removeElement(final Stamped<E> elem) {
if (elem == null) {
return;
}
if (ascendingSubsequence.peekFirst() == elem) {
ascendingSubsequence.removeFirst();
}
if (ascendingSubsequence.isEmpty()) {
lastKnownTime = elem.timestamp;
}
}
public int size() {
return ascendingSubsequence.size();
}
/**
* @return the lowest tracked timestamp
*/
public long get() {
Stamped<E> stamped = ascendingSubsequence.peekFirst();
if (stamped == null)
return lastKnownTime;
else
return stamped.timestamp;
}
}