/**
* 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 storm.starter.tools;
import backtype.storm.utils.Time;
import org.apache.commons.collections.buffer.CircularFifoBuffer;
/**
* This class tracks the time-since-last-modify of a "thing" in a rolling fashion.
* <p/>
* For example, create a 5-slot tracker to track the five most recent time-since-last-modify.
* <p/>
* You must manually "mark" that the "something" that you want to track -- in terms of modification times -- has just
* been modified.
*/
public class NthLastModifiedTimeTracker {
private static final int MILLIS_IN_SEC = 1000;
private final CircularFifoBuffer lastModifiedTimesMillis;
public NthLastModifiedTimeTracker(int numTimesToTrack) {
if (numTimesToTrack < 1) {
throw new IllegalArgumentException(
"numTimesToTrack must be greater than zero (you requested " + numTimesToTrack + ")");
}
lastModifiedTimesMillis = new CircularFifoBuffer(numTimesToTrack);
initLastModifiedTimesMillis();
}
private void initLastModifiedTimesMillis() {
long nowCached = now();
for (int i = 0; i < lastModifiedTimesMillis.maxSize(); i++) {
lastModifiedTimesMillis.add(Long.valueOf(nowCached));
}
}
private long now() {
return Time.currentTimeMillis();
}
public int secondsSinceOldestModification() {
long modifiedTimeMillis = ((Long) lastModifiedTimesMillis.get()).longValue();
return (int) ((now() - modifiedTimeMillis) / MILLIS_IN_SEC);
}
public void markAsModified() {
updateLastModifiedTime();
}
private void updateLastModifiedTime() {
lastModifiedTimesMillis.add(now());
}
}