threadpool.java

低版本的tomcat 对于有些老版本的应用还真的需要老版的中间件

/*
 * $Header: /home/cvs/jakarta-tomcat/src/share/org/apache/tomcat/util/Attic/ThreadPool.java,v 1.9.2.3 2001/08/25 01:01:41 nacho Exp $
 * $Revision: 1.9.2.3 $
 * $Date: 2001/08/25 01:01:41 $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
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 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
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 *    permission, please contact [e-mail].
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 * 5. Products derived from this software may not be called "Apache"
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 * ====================================================================
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 * This software consists of voluntary contributions made by many
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 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * [Additional notices, if required by prior licensing conditions]
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package org.apache.tomcat.util;

import java.util.zip.*;
import java.net.*;
import java.util.*;
import java.io.*;

import org.apache.tomcat.logging.*; 

/**
 * A thread pool that is trying to copy the apache process management.
 *
 * @author Gal Shachor
 */
public class ThreadPool  {

    /*
     * Default values ...
     */
    public static final int MAX_THREADS = 100;
    public static final int MAX_SPARE_THREADS = 50;
    public static final int MIN_SPARE_THREADS = 10;
    public static final int WORK_WAIT_TIMEOUT = 60*1000;

    /*
     * Where the threads are held.
     */
    protected Vector pool;

    /*
     * A monitor thread that monitors the pool for idel threads.
     */
    protected MonitorRunnable monitor;


    /*
     * Max number of threads that you can open in the pool.
     */
    protected int maxThreads;

    /*
     * Min number of idel threads that you can leave in the pool.
     */
    protected int minSpareThreads;

    /*
     * Max number of idel threads that you can leave in the pool.
     */
    protected int maxSpareThreads;

    /*
     * Number of threads in the pool.
     */
    protected int currentThreadCount;

    /*
     * Number of busy threads in the pool.
     */
    protected int currentThreadsBusy;

    /*
     * Flag that the pool should terminate all the threads and stop.
     */
    protected boolean stopThePool;

    static int debug=0;

    /**
     * Helper object for logging
     **/
    LogHelper loghelper = new LogHelper("tc_log", "ThreadPool");
    
    public ThreadPool() {
        maxThreads      = MAX_THREADS;
        maxSpareThreads = MAX_SPARE_THREADS;
        minSpareThreads = MIN_SPARE_THREADS;
        currentThreadCount  = 0;
        currentThreadsBusy  = 0;
        stopThePool = false;
    }

    public synchronized void start() {
        adjustLimits();

        openThreads(minSpareThreads);
        monitor = new MonitorRunnable(this);
    }

    public void setMaxThreads(int maxThreads) {
        this.maxThreads = maxThreads;
    }

    public int getMaxThreads() {
        return maxThreads;
    }

    public void setMinSpareThreads(int minSpareThreads) {
        this.minSpareThreads = minSpareThreads;
    }

    public int getMinSpareThreads() {
        return minSpareThreads;
    }

    public void setMaxSpareThreads(int maxSpareThreads) {
        this.maxSpareThreads = maxSpareThreads;
    }

    public int getMaxSpareThreads() {
        return maxSpareThreads;
    }

    //
    // You may wonder what you see here ... basically I am trying
    // to maintain a stack of threads. This way locality in time
    // is kept and there is a better chance to find residues of the
    // thread in memory next time it runs.
    //

    /**
     * Executes a given Runnable on a thread in the pool, block if needed.
     */
    public void runIt(ThreadPoolRunnable r) {

        if(null == r) {
            throw new NullPointerException();
        }

        if(0 == currentThreadCount || stopThePool) {
            throw new IllegalStateException();
        }

        ControlRunnable c = null;

        // Obtain a free thread from the pool.
        synchronized(this) {
            if(currentThreadsBusy == currentThreadCount) {
                 // All threads are busy
                if(currentThreadCount < maxThreads) {
                    // Not all threads were open,
                    // Open new threads up to the max number of idel threads
                    int toOpen = currentThreadCount + minSpareThreads;
                    openThreads(toOpen);
                } else {
                    // XXX There really should be a way to log which pool is exhuasted
                    loghelper.log("Pool exhausted with " + currentThreadCount + " threads.");

                    // Wait for a thread to become idel.
                    while(currentThreadsBusy == currentThreadCount) {
                        try {
                            this.wait();
                        }
			// was just catch Throwable -- but no other
			// exceptions can be thrown by wait, right?
			// So we catch and ignore this one, since
			// it'll never actually happen, since nowhere
			// do we say pool.interrupt().
			catch(InterruptedException e) {
			    loghelper.log("Unexpected exception", e);
                        }

                        // Pool was stopped. Get away of the pool.
                        if(0 == currentThreadCount || stopThePool) {
                            throw new IllegalStateException();
                        }
                    }
                }
            }

            // If we are here it means that there is a free thred. Take it.
            c = (ControlRunnable)pool.lastElement();
            pool.removeElement(c);
            currentThreadsBusy++;
        }
        c.runIt(r);
    }

    /**
     * Stop the thread pool
     */
    public synchronized void shutdown() {
        if(!stopThePool) {
            stopThePool = true;
            monitor.terminate();
            monitor = null;
            for(int i = 0 ; i < (currentThreadCount - currentThreadsBusy) ; i++) {
                try {
                    ((ControlRunnable)(pool.elementAt(i))).terminate();
                } catch(Throwable t) {
                    /* 
					 * Do nothing... The show must go on, we are shutting 
					 * down the pool and nothing should stop that.
					 */
		    loghelper.log("Ignored exception while shutting down thread pool", t, Logger.ERROR);
                }
            }
            currentThreadsBusy = currentThreadCount = 0;
            pool = null;
            notifyAll();
        }
    }

    /**
     * Called by the monitor thread to harvest idel threads.
     */
    protected synchronized void checkSpareControllers() {

        if(stopThePool) {
            return;
        }
        if((currentThreadCount - currentThreadsBusy) > maxSpareThreads) {
            int toFree = currentThreadCount -
                         currentThreadsBusy -
                         maxSpareThreads;