package io.dropwizard.metrics;
import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
/**
* A metric which calculates the distribution of a value.
*
* @see <a href="http://www.johndcook.com/standard_deviation.html">Accurately computing running
* variance</a>
*/
public class Histogram implements Metric, Sampling, Counting {
private final Reservoir reservoir;
private final LongAdder count;
/**
* Creates a new {@link Histogram} with the given reservoir.
*
* @param reservoir the reservoir to create a histogram from
*/
public Histogram(Reservoir reservoir) {
this.reservoir = reservoir;
this.count = LongAdderFactory.create();
}
/**
* Adds a recorded value.
*
* @param value the length of the value
*/
public void update(int value) {
update((long) value);
}
/**
* Adds a recorded value.
*
* @param value the length of the value
*/
public void update(long value) {
count.increment();
reservoir.update(value);
}
/**
* Returns the number of values recorded.
*
* @return the number of values recorded
*/
@Override
public long getCount() {
return count.sum();
}
@Override
public Snapshot getSnapshot() {
return reservoir.getSnapshot();
}
@Override
public String toString() {
final ByteArrayOutputStream out = new ByteArrayOutputStream();
this.getSnapshot().dump(out);
try {
return out.toString(StandardCharsets.UTF_8.name());
} catch (UnsupportedEncodingException e) {
return super.toString();
}
}
}