/**
* Adds an old value with a fixed timestamp to the sample.
*
* @param value the value to be added
* @param timestamp the epoch timestamp of {@code value} in seconds
*/
public void update(long value, long timestamp) {
lockForRegularUsage();
try {
final double priority = weight(timestamp - startTime) / random();
final long newCount = count.incrementAndGet();
if (newCount <= reservoirSize) {
values.put(priority, value);
} else {
Double first = values.firstKey();
if (first < priority) {
if (values.putIfAbsent(priority, value) == null) {
// ensure we always remove an item
while (values.remove(first) == null) {
first = values.firstKey();
}
}
}
}
} finally {
unlockForRegularUsage();
}
final long now = System.nanoTime();
final long next = nextScaleTime.get();
if (now >= next) {
rescale(now, next);
}
}
/** Stops execution time measurement. */
public void stop() {
add(System.nanoTime() - startClock);
}
/** Starts execution time measurement. */
public void start() {
startClock = System.nanoTime();
}
public void clear() {
values.clear();
count.set(0);
this.startTime = tick();
nextScaleTime.set(System.nanoTime() + RESCALE_THRESHOLD);
}
private static long tick() {
return TimeUnit.NANOSECONDS.toSeconds(System.nanoTime());
}