package com.mapr.synth.samplers;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.TextNode;
import com.google.common.collect.ImmutableMap;
import org.apache.mahout.common.RandomUtils;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Samples progressive times that look like event arrival times.
* <p/>
* You can set the
* <p/>
* <il>
* <li><em>rate</em> - use something like 5/m to indicate 5 events per minute. The unit is optional, seconds are the default.</li>
* <li><em>offset</em> - the minimum time between events, default is 0</li>
* <li><em>format </em>- the format to use when outputting the times</li>
* <li><em>start </em>- the time of the first event</li>
* </il>
*
* Thread safe
*/
public class ArrivalSampler extends FieldSampler {
private final Random base;
private final Pattern ratePattern = Pattern.compile("([0-9.e\\-]+)(/[smhd])?");
private final Map<String, TimeUnit> unitMap = ImmutableMap.of(
"s", TimeUnit.SECONDS,
"m", TimeUnit.MINUTES,
"h", TimeUnit.HOURS,
"d", TimeUnit.DAYS);
private double meanInterval = 1000; // interval - offset will have this mean
private double minInterval = 0; // no interval can be less than this
private SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
private double start = System.currentTimeMillis();
public ArrivalSampler() {
base = RandomUtils.getRandom();
}
@SuppressWarnings("UnusedDeclaration")
public void setRate(String rate) {
Matcher m = ratePattern.matcher(rate);
if (m.matches()) {
// group(1) is the number, group(2) is either empty (default to /s) or /d or some such.
TimeUnit sourceUnit = (m.groupCount() > 1) ? unitMap.get(m.group(2).substring(1)) : TimeUnit.SECONDS;
double count = Double.parseDouble(m.group(1));
this.meanInterval = TimeUnit.MILLISECONDS.convert(1, sourceUnit) / count;
} else {
throw new IllegalArgumentException(String.format("Invalid rate argument: %s", rate));
}
}
@SuppressWarnings("UnusedDeclaration")
public void setOffset(double offset) {
minInterval = offset;
}
public void setFormat(String format) {
df = new SimpleDateFormat(format);
}
@SuppressWarnings("UnusedDeclaration")
public void setStart(String start) throws ParseException {
this.start = df.parse(start).getTime();
}
@Override
public JsonNode sample() {
synchronized (this) {
TextNode r = new TextNode(df.format(new Date((long) start)));
start += minInterval - meanInterval * Math.log(1 - base.nextDouble());
return r;
}
}
}