threadpoolcontroller.java

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

/* 
 * Copyright (c) 2001 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.sandStorm.internal;

import seda.sandStorm.api.*;
import seda.sandStorm.api.internal.*;
import seda.sandStorm.core.*;
import seda.sandStorm.main.*;
import java.util.*;

/**
 * The ThreadPoolController is responsible for dynamically adusting the 
 * size of a given ThreadPool.
 * 
 * @author   Matt Welsh
 */

public class ThreadPoolController {

  private static final boolean DEBUG = false;

  // Multiple of standard controller delay 
  private static final int CONTROLLER_DELAY = 4;

  // Multiple of standard controller delay 
  private static final int THROUGHPUT_MEASUREMENT_DELAY = 1;

  // Multiple of standard controller delay 
  private static final int AUTO_MAX_DETECT_DELAY = 10;

  // Size of random jump down in number of threads
  private static final int AUTO_MAX_DETECT_RANDOM_JUMP = 4;
  
  private static final double SMOOTH_CONST = 0.3;

  private ManagerIF mgr;
  private Vector tpvec;

  private boolean autoMaxDetect;
  private Thread controller;
  private int controllerDelay, controllerThreshold;

  public ThreadPoolController(ManagerIF mgr) {
    this.mgr = mgr;
    tpvec = new Vector();

    SandstormConfig config = mgr.getConfig();
    this.controllerDelay = config.getInt("global.threadPool.sizeController.delay");
    this.controllerThreshold = config.getInt("global.threadPool.sizeController.threshold");
    this.autoMaxDetect = config.getBoolean("global.threadPool.sizeController.autoMaxDetect");

    start();
  }

  public ThreadPoolController(ManagerIF mgr, int delay, int threshold) {
    this.mgr = mgr;
    tpvec = new Vector();
    this.controllerDelay = delay;
    SandstormConfig config = mgr.getConfig();
    if (this.controllerDelay == -1) {
      this.controllerDelay = config.getInt("global.threadPool.sizeController.delay");
    }
    this.controllerThreshold = threshold;
    if (this.controllerThreshold == -1) {
      this.controllerThreshold = config.getInt("global.threadPool.sizeController.threshold");
    }

    this.autoMaxDetect = config.getBoolean("global.threadPool.sizeController.autoMaxDetect");
    start();
  }

  /**
   * Register a thread pool with this controller, using the queue threshold
   * specified by the system configuration.
   */
  public void register(StageWrapperIF stage, ThreadPool tp) {
    SandstormConfig config = mgr.getConfig();
    int thresh = config.getInt("stages."+stage.getStage().getName()+".threadPool.sizeController.threshold", controllerThreshold);
    tpvec.addElement(new tpcClient(stage, tp, null, thresh));
  }

  /**
   * Register a thread pool with this controller, using the queue threshold
   * specified by the system configuration.
   */
  public void register(StageWrapperIF stage, ThreadPool tp, ProfilableIF metric) {
    tpvec.addElement(new tpcClient(stage, tp, metric, controllerThreshold));
  }

  private void start() {
    System.err.println("ThreadPoolController: Started, delay "+controllerDelay+" ms, threshold "+controllerThreshold+", autoMaxDetect "+autoMaxDetect);
    controller = new Thread(new controllerThread(), "TPC");
    controller.start();
  }

  /**
   * Internal class representing a single TPC-controlled thread pool.
   */
  class tpcClient {
    private StageWrapperIF stage;
    private ThreadPool tp;
    private int threshold;
    private ProfilableIF metric;

    int savedThreads, avgThreads;
    long savedTotalEvents;
    double savedThroughput, avgThroughput;
    long last_time, reset_time;

    tpcClient(final StageWrapperIF stage, ThreadPool tp, ProfilableIF metric, int threshold) {
      this.stage = stage;
      this.tp = tp;
      this.threshold = threshold;
      this.metric = metric;
      if (this.metric == null) {
	this.metric = new ProfilableIF() {
	  public int profileSize() {
	    return stage.getSource().size();
	  }
	};
      }

      savedThreads = tp.numThreads();
      reset_time = last_time = System.currentTimeMillis();

      mgr.getProfiler().add("TPController savedThreads <"+stage.getStage().getName()+">",
	  new ProfilableIF() {
	  public int profileSize() {
  	  return (int)savedThreads;
	  }
	  });

      mgr.getProfiler().add("TPController avgThreads <"+stage.getStage().getName()+">",
	  new ProfilableIF() {
	  public int profileSize() {
  	  return (int)avgThreads;
	  }
	  });

      mgr.getProfiler().add("TPController savedThroughput <"+stage.getStage().getName()+">",
	  new ProfilableIF() {
	  public int profileSize() {
  	  return (int)savedThroughput;
	  }
	  });

      mgr.getProfiler().add("TPController avgThroughput <"+stage.getStage().getName()+">",
	  new ProfilableIF() {
	  public int profileSize() {
  	  return (int)avgThroughput;
	  }
	  });
    }
  }

  /**
   * Internal class implementing the controller.
   */
  class controllerThread implements Runnable {

    int adjust_count = 0;
    Random rand;

    controllerThread() {
      rand = new Random();
    }

    public void run() {
      if (DEBUG) System.err.println("TP size controller: starting");

      while (true) {
	adjustThreadPools();
	try {
	  Thread.currentThread().sleep(controllerDelay);
	} catch (InterruptedException ie) {
	  // Ignore
	}
      }
    }

    private void adjustThreadPools() {

      adjust_count++;

      if ((adjust_count % CONTROLLER_DELAY) == 0) { 

	for (int i = 0; i < tpvec.size(); i++) {
	  tpcClient tpc = (tpcClient)tpvec.elementAt(i);

	  //if (DEBUG) System.err.println("TP controller: Inspecting "+tpc.tp);

	  int sz = tpc.metric.profileSize();
	  //if (DEBUG) System.err.println("TP controller: "+tpc.tp+" has size "+sz+", threshold "+tpc.threshold);
	  boolean addThread = false;
	  if (sz >= tpc.threshold) addThread = true;

	  if (addThread) {
	    tpc.tp.addThreads(1, true);
	  }
	}
      }

      if ((DEBUG || autoMaxDetect) &&
	  (adjust_count % THROUGHPUT_MEASUREMENT_DELAY) == 0) {

	long curTime = System.currentTimeMillis();

	for (int i = 0; i < tpvec.size(); i++) {
	  tpcClient tpc = (tpcClient)tpvec.elementAt(i);

	  StageWrapper sw;
	  try {
	    sw = (StageWrapper)tpc.stage;
	  } catch (ClassCastException se) {
	    // Skip this one
	    continue;
	  }

	  long events = sw.getStats().getTotalEvents();
	  long curEvents = events - tpc.savedTotalEvents;
	  tpc.savedTotalEvents = events;
	  if (DEBUG) System.err.println("TP <"+tpc.stage.getStage().getName()+"> events "+events+" curEvents "+curEvents);

	  int curThreads = tpc.tp.numThreads();
	  tpc.avgThreads = (int)((SMOOTH_CONST * curThreads) + ((1.0 - SMOOTH_CONST) * (double)(tpc.avgThreads * 1.0)));

	  //double throughput = (sw.getStats().getServiceRate() * curThreads);
	  double throughput = (curEvents * 1.0) / ((curTime - tpc.last_time) * 1.0e-3);
	  tpc.avgThroughput = (SMOOTH_CONST * throughput) + ((1.0 - SMOOTH_CONST) * (double)(tpc.avgThroughput * 1.0));
	  if (DEBUG) System.err.println("TP <"+tpc.stage.getStage().getName()+"> throughput "+tpc.avgThroughput);
	  tpc.last_time = curTime;
	}
      }

      if (autoMaxDetect && (adjust_count % AUTO_MAX_DETECT_DELAY) == 0) {

	for (int i = 0; i < tpvec.size(); i++) {
	  tpcClient tpc = (tpcClient)tpvec.elementAt(i);

	  // Periodically override saved values
	  //long tr = curTime - tpc.reset_time;
	  //if (rand.nextDouble() < 1.0 - Math.exp(-1.0 * (tr / 1e5))) 
	  //  System.err.println("TP controller <"+tpc.stage.getStage().getName()+"> Resetting saved values");
	  //  tpc.reset_time = curTime;
	  //  tpc.savedThreads = tpc.avgThreads;
	  //  tpc.savedThroughput = tpc.avgThroughput;

	  // Make random jump down
	  // int nt = (int)(rand.nextDouble() * AUTO_MAX_DETECT_RANDOM_JUMP);
	  // tpc.tp.removeThreads(nt);
	  //

	  //continue;

	  if (tpc.avgThroughput >= (1.0 * tpc.savedThroughput)) {
	    // Accept new state

	    tpc.savedThreads = tpc.tp.numThreads();
	    tpc.savedThroughput = tpc.avgThroughput;
	    if (DEBUG) System.err.println("TP controller <"+tpc.stage.getStage().getName()+"> Setting new state to threads="+tpc.savedThreads+" tp="+tpc.savedThroughput);

	    //	  else if (tpc.avgThroughput <= (1.2 * tpc.savedThroughput)) 
	    // We are degrading: halve the number of threads

	    //	    int numThreads = tpc.tp.numThreads();
	    //	    int newThreads = Math.max(1, numThreads / 2);
	    //	    System.err.println("TP controller <"+tpc.stage.getStage().getName()+"> Degrading (tp="+tpc.avgThroughput+") Reverting to threads="+tpc.savedThreads+"/"+newThreads+" stp="+tpc.savedThroughput);
	    //     	    if (newThreads < numThreads) 
	    //	      tpc.tp.removeThreads(numThreads - newThreads);
	    //	    tpc.savedThroughput = tpc.avgThroughput;
	    //	    tpc.savedThreads = newThreads;

	  } else if (tpc.avgThroughput <= (1.2 * tpc.savedThroughput)) {
	    // Otherwise reset to savedThreads (minus random jump down)
	    // as long as the number of threads is different

	    if (tpc.savedThreads != tpc.tp.numThreads()) {
	      int numThreads = tpc.tp.numThreads();
	      int nt = (int)(rand.nextDouble() * AUTO_MAX_DETECT_RANDOM_JUMP);
	      int newThreads = Math.max(1, tpc.savedThreads - nt);

	      if (DEBUG || autoMaxDetect) System.err.println("TP controller <"+tpc.stage.getStage().getName()+"> Reverting to threads="+tpc.savedThreads+"/"+newThreads+" stp="+tpc.savedThroughput);

	      if (newThreads < numThreads) { 
		// Remove threads
		tpc.tp.removeThreads(numThreads - newThreads);
	      } else if (newThreads > numThreads) {
		// Add threads
		tpc.tp.addThreads(newThreads - numThreads, true);
	      }
	    }
	  }
	}
	return;
      }

    }
  }
}