statsgatherer.java

The Staged Event-Driven Architecture (SEDA) is a new design for building scalable Internet services.

/* 
 * Copyright (c) 2002 by Matt Welsh and The Regents of the University of 
 * California. All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without written agreement is
 * hereby granted, provided that the above copyright notice and the following
 * two paragraphs appear in all copies of this software.
 * 
 * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
 * CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 * Author: Matt Welsh <[e-mail]>
 * 
 */

package seda.util;
import java.util.*;

public class StatsGatherer {

  private Hashtable histogram;
  private int bucketSize;
  private String name;
  private String tag;
  private double mean = -1;

  private int skipSamples;
  private int skip = 0;
  public int num = 0;
  public double maxVal = 0;
  public double minVal = Double.MAX_VALUE;
  public double cumulativeVal = 0;

  private static Hashtable sgTbl = new Hashtable();

  public StatsGatherer(String name, String tag, int bucketSize, int skipSamples) {
    this.name = name;
    this.tag = tag;
    this.bucketSize = bucketSize;
    this.skipSamples = skipSamples;
    if (bucketSize != 0) {
      histogram = new Hashtable(1);
    }
    sgTbl.put(name, this);
  }

  public StatsGatherer(String name, String tag, int bucketSize) {
    this(name, tag, bucketSize, 0);
  }

  public static StatsGatherer lookup(String name) {
    return (StatsGatherer)sgTbl.get(name);
  }

  public static Enumeration lookupAll() {
    return sgTbl.elements();
  }

  public static void dumpAll() {
    Enumeration e = lookupAll();
    while (e.hasMoreElements()) {
      StatsGatherer sg = (StatsGatherer)e.nextElement();
      sg.dumpHistogram();
    }
  }

  public synchronized void reset() {
    this.num = 0;
    this.maxVal = 0;
    this.minVal = Double.MAX_VALUE;
    this.cumulativeVal = 0;
    if (bucketSize != 0) {
      histogram = new Hashtable(1);
    }
  }

  public synchronized void add(double val) {
    if (skip < skipSamples) {
      skip++;
      return;
    }

    num++;

    if (val > maxVal) maxVal = val;
    if (val < minVal) minVal = val;
    cumulativeVal += val;

    if (bucketSize != 0) {
      Integer ct = new Integer((int)val / bucketSize);
      Integer bval = (Integer)histogram.remove(ct);

      if (bval == null) {
	histogram.put(ct, new Integer(1));
      } else {
	bval = new Integer(bval.intValue() + 1);
	histogram.put(ct, bval);
      }
    }
  }

  public synchronized void dumpHistogram() {
    System.err.println("=== Histogram dump of StatsGatherer: "+name+" ===");

    TreeSet ts = new TreeSet(new Comparator() {
	public int compare(Object o1, Object o2) {
  	  Integer i1 = (Integer)o1;
	  Integer i2 = (Integer)o2;
	  if (i1.intValue() == i2.intValue()) return 0;
	  else if (i1.intValue() < i2.intValue()) return -1;
	  else return 1;
	}
	});

    ts.addAll(histogram.keySet());

    Object arr[] = ts.toArray();
    for (int i = 0; i < arr.length; i++) {
      Integer bucket = (Integer)arr[i];
      int time = bucket.intValue() * bucketSize;
      int val = ((Integer)histogram.get(bucket)).intValue();
      System.err.println(tag+" "+time+" ms "+MDWUtil.format(val)+" count "+MDWUtil.format((val*100.0)/(num*1.0))+" pct");
    }
    System.err.println("=== Summary of StatsGatherer: "+name+" ===");
    System.err.println(tag+": num "+num+" avg "+mean()+" max "+max()+" 90th "+percentile(0.9));
    System.err.println("=== End of summmary for StatsGatherer: "+name+" ===");
    System.err.println("\n");
  }

  public synchronized int num() {
    return num;
  }

  public synchronized double mean() {
    if (num == 0) return 0.0;
    return (cumulativeVal * 1.0)/num;
  }

  public synchronized double min() {
    return minVal;
  }

  public synchronized double max() {
    return maxVal;
  }

  public synchronized double percentile(double pct) {
    if (num == 0) return 0.0;
    double data[] = new double[num];
    int n = 0;
    Enumeration e = histogram.keys();
    while (e.hasMoreElements()) {
      Integer bucket = (Integer)e.nextElement();
      int time = bucket.intValue() * bucketSize;
      int val = ((Integer)histogram.get(bucket)).intValue();
      for (int j = 0; j < val; j++) {
	data[n++] = time;
      }
    }
    Arrays.sort(data);
    int index = (int)(data.length * pct);
    return data[index];
  }

}