FixedThreadPool.java

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package com.sun.grizzly.util;

import java.util.Queue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;

/**
 * minimalistic fixed threadpool to allow for nice scalability if a
 * good Queue impl is used.
 * by default: {@link WorkerThreadImpl} is used,
 *
 * @author gustav trede
 */
public class FixedThreadPool extends AbstractThreadPool {

    private int expectedWorkerCount;
    protected final BlockingQueue<Runnable> workQueue;

    /**
     * creates a fixed pool of size 8
     */
    public FixedThreadPool() {
        this(8);
    }

    /**
     *
     * @param size
     */
    public FixedThreadPool(int size) {
        this(size, FixedThreadPool.class.getSimpleName());
    }

    /**
     *
     * @param poolsize
     * @param name
     */
    public FixedThreadPool(int poolsize, String name) {
        this(name, poolsize, DataStructures.getLTQinstance(Runnable.class), null);
    }

    /**
     * 
     * @param poolsize
     * @param threadfactory
     */
    public FixedThreadPool(int poolsize, ThreadFactory threadfactory) {
        this(poolsize, DataStructures.getLTQinstance(Runnable.class),
                threadfactory);
    }

    /**
     * 
     * @param poolsize
     * @param workQueue
     * @param threadfactory
     */
    public FixedThreadPool(int poolsize, BlockingQueue<Runnable> workQueue,
            ThreadFactory threadfactory) {
        this(FixedThreadPool.class.getSimpleName(),
                poolsize, workQueue, threadfactory);
    }

    /**
     *
     * @param name
     * @param poolsize
     * @param workQueue
     * @param threadfactory
     */
    public FixedThreadPool(String name, int poolsize,
            BlockingQueue<Runnable> workQueue,ThreadFactory threadfactory) {
        this(name, poolsize, workQueue, threadfactory, null);
    }

    /**
     *
     * @param name
     * @param poolsize
     * @param workQueue
     * @param threadfactory
     * @param probe 
     */
    public FixedThreadPool(String name, int poolsize,
            BlockingQueue<Runnable> workQueue, ThreadFactory threadfactory,
            ThreadPoolMonitoringProbe probe) {
        super(probe, name, threadfactory,poolsize);
        this.workQueue = workQueue != null ? workQueue :
            DataStructures.getLTQinstance(Runnable.class);
        synchronized (statelock) {
            while (poolsize-- > 0) {
                doStartWorker();
            }
        }
        super.onMaxNumberOfThreadsReached();
    }

    @Override
    public final void setMaximumPoolSize(int maximumPoolSize) {
        if (maximumPoolSize < 1) {
            throw new IllegalStateException("maximumPoolSize < 1");
        }
        synchronized (statelock) {
            if (running) {
                this.maxPoolSize = maximumPoolSize;
                int toAdd = maximumPoolSize - expectedWorkerCount;
                while (toAdd > 0) {
                    toAdd--;
                    doStartWorker();
                }
                while (toAdd++ < 0) {
                    workQueue.add(poison);
                    expectedWorkerCount--;
                }
                super.onMaxNumberOfThreadsReached();
            }
        }
    }

    /**
     * Must hold statelock while calling this method.
     * @param wt
     */
    private void doStartWorker() {
        startWorker(new BasicWorker());
        expectedWorkerCount++;
    }

    public void execute(Runnable command) {
        if (running) {
            if (workQueue.offer(command)) {
                onTaskQueued(command);
                return;
            }
            onTaskQueueOverflow();
            return;
        }
        throw new RejectedExecutionException("ThreadPool is not running");
    }

    /**
     * not supported
     */
    public boolean isTerminated() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    /**
     * not supported
     */
    public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    public int getActiveCount() {
        return 0;
    }

    public int getTaskCount() {
        return 0;
    }

    public long getCompletedTaskCount() {
        return 0;
    }

    @Override
    public void setCorePoolSize(int corePoolSize) {
    }

    public int getLargestPoolSize() {
        return maxPoolSize;
    }

    public int getPoolSize() {
        return maxPoolSize;
    }

    public Queue<Runnable> getQueue() {
        return workQueue;
    }

    public int getQueueSize() {
        return workQueue.size();
    }

    public int getMaxQueuedTasksCount() {
        return -1;
    }

    public void setMaxQueuedTasksCount(int maxTasksCount) {
    }

    private final class BasicWorker extends Worker {
        protected final Runnable getTask() throws InterruptedException {
            return workQueue.take();
        }
    }
}