package storm.starter.tools;
import org.apache.commons.collections.buffer.CircularFifoBuffer;
import backtype.storm.utils.Time;
/**
* This class tracks the time-since-last-modify of a "thing" in a rolling fashion.
*
* For example, create a 5-slot tracker to track the five most recent time-since-last-modify.
*
* 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());
}
}