/*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package com.sun.corba.se.impl.orbutil.threadpool;
import java.security.AccessController;
import java.security.PrivilegedAction;
import com.sun.corba.se.spi.orbutil.threadpool.NoSuchWorkQueueException;
import com.sun.corba.se.spi.orbutil.threadpool.ThreadPool;
import com.sun.corba.se.spi.orbutil.threadpool.Work;
import com.sun.corba.se.spi.orbutil.threadpool.WorkQueue;
import com.sun.corba.se.impl.orbutil.ORBConstants;
import com.sun.corba.se.impl.orbutil.threadpool.WorkQueueImpl;
import com.sun.corba.se.spi.monitoring.MonitoringConstants;
import com.sun.corba.se.spi.monitoring.MonitoredObject;
import com.sun.corba.se.spi.monitoring.MonitoringFactories;
import com.sun.corba.se.spi.monitoring.LongMonitoredAttributeBase;
public class ThreadPoolImpl implements ThreadPool
{
private static int threadCounter = 0; // serial counter useful for debugging
private WorkQueue workQueue;
// Stores the number of available worker threads
private int availableWorkerThreads = 0;
// Stores the number of threads in the threadpool currently
private int currentThreadCount = 0;
// Minimum number of worker threads created at instantiation of the threadpool
private int minWorkerThreads = 0;
// Maximum number of worker threads in the threadpool
private int maxWorkerThreads = 0;
// Inactivity timeout value for worker threads to exit and stop running
private long inactivityTimeout = ORBConstants.DEFAULT_INACTIVITY_TIMEOUT ;
// Indicates if the threadpool is bounded or unbounded
private boolean boundedThreadPool = false;
// Running count of the work items processed
// Set the value to 1 so that divide by zero is avoided in
// averageWorkCompletionTime()
private long processedCount = 1;
// Running aggregate of the time taken in millis to execute work items
// processed by the threads in the threadpool
private long totalTimeTaken = 0;
// Lock for protecting state when required
private Object lock = new Object();
// Name of the ThreadPool
private String name;
// MonitoredObject for ThreadPool
private MonitoredObject threadpoolMonitoredObject;
// ThreadGroup in which threads should be created
private final ThreadGroup threadGroup ;
/**
* This constructor is used to create an unbounded threadpool
*/
public ThreadPoolImpl(ThreadGroup tg, String threadpoolName) {
maxWorkerThreads = Integer.MAX_VALUE;
workQueue = new WorkQueueImpl(this);
threadGroup = tg ;
name = threadpoolName;
initializeMonitoring();
}
/**
* This constructor is used to create an unbounded threadpool
* in the ThreadGroup of the current thread
*/
public ThreadPoolImpl(String threadpoolName) {
this( Thread.currentThread().getThreadGroup(), threadpoolName ) ;
}
/**
* This constructor is used to create bounded threadpool
*/
public ThreadPoolImpl(int minSize, int maxSize, long timeout,
String threadpoolName)
{
inactivityTimeout = timeout;
minWorkerThreads = minSize;
maxWorkerThreads = maxSize;
boundedThreadPool = true;
workQueue = new WorkQueueImpl(this);
threadGroup = Thread.currentThread().getThreadGroup() ;
name = threadpoolName;
for (int i = 0; i < minWorkerThreads; i++) {
createWorkerThread();
}
initializeMonitoring();
}
// Setup monitoring for this threadpool
private void initializeMonitoring() {
// Get root monitored object
MonitoredObject root = MonitoringFactories.getMonitoringManagerFactory().
createMonitoringManager(MonitoringConstants.DEFAULT_MONITORING_ROOT, null).
getRootMonitoredObject();
// Create the threadpool monitoring root
MonitoredObject threadPoolMonitoringObjectRoot = root.getChild(
MonitoringConstants.THREADPOOL_MONITORING_ROOT);
if (threadPoolMonitoringObjectRoot == null) {
threadPoolMonitoringObjectRoot = MonitoringFactories.
getMonitoredObjectFactory().createMonitoredObject(
MonitoringConstants.THREADPOOL_MONITORING_ROOT,
MonitoringConstants.THREADPOOL_MONITORING_ROOT_DESCRIPTION);
root.addChild(threadPoolMonitoringObjectRoot);
}
threadpoolMonitoredObject = MonitoringFactories.
getMonitoredObjectFactory().
createMonitoredObject(name,
MonitoringConstants.THREADPOOL_MONITORING_DESCRIPTION);
threadPoolMonitoringObjectRoot.addChild(threadpoolMonitoredObject);
LongMonitoredAttributeBase b1 = new
LongMonitoredAttributeBase(MonitoringConstants.THREADPOOL_CURRENT_NUMBER_OF_THREADS,
MonitoringConstants.THREADPOOL_CURRENT_NUMBER_OF_THREADS_DESCRIPTION) {
public Object getValue() {
return new Long(ThreadPoolImpl.this.currentNumberOfThreads());
}
};
threadpoolMonitoredObject.addAttribute(b1);
LongMonitoredAttributeBase b2 = new
LongMonitoredAttributeBase(MonitoringConstants.THREADPOOL_NUMBER_OF_AVAILABLE_THREADS,
MonitoringConstants.THREADPOOL_CURRENT_NUMBER_OF_THREADS_DESCRIPTION) {
public Object getValue() {
return new Long(ThreadPoolImpl.this.numberOfAvailableThreads());
}
};
threadpoolMonitoredObject.addAttribute(b2);
LongMonitoredAttributeBase b3 = new
LongMonitoredAttributeBase(MonitoringConstants.THREADPOOL_NUMBER_OF_BUSY_THREADS,
MonitoringConstants.THREADPOOL_NUMBER_OF_BUSY_THREADS_DESCRIPTION) {
public Object getValue() {
return new Long(ThreadPoolImpl.this.numberOfBusyThreads());
}
};
threadpoolMonitoredObject.addAttribute(b3);
LongMonitoredAttributeBase b4 = new
LongMonitoredAttributeBase(MonitoringConstants.THREADPOOL_AVERAGE_WORK_COMPLETION_TIME,
MonitoringConstants.THREADPOOL_AVERAGE_WORK_COMPLETION_TIME_DESCRIPTION) {
public Object getValue() {
return new Long(ThreadPoolImpl.this.averageWorkCompletionTime());
}
};
threadpoolMonitoredObject.addAttribute(b4);
LongMonitoredAttributeBase b5 = new
LongMonitoredAttributeBase(MonitoringConstants.THREADPOOL_CURRENT_PROCESSED_COUNT,
MonitoringConstants.THREADPOOL_CURRENT_PROCESSED_COUNT_DESCRIPTION) {
public Object getValue() {
return new Long(ThreadPoolImpl.this.currentProcessedCount());
}
};
threadpoolMonitoredObject.addAttribute(b5);
// Add the monitored object for the WorkQueue
threadpoolMonitoredObject.addChild(
((WorkQueueImpl)workQueue).getMonitoredObject());
}
// Package private method to get the monitored object for this
// class
MonitoredObject getMonitoredObject() {
return threadpoolMonitoredObject;
}
public WorkQueue getAnyWorkQueue()
{
return workQueue;
}
public WorkQueue getWorkQueue(int queueId)
throws NoSuchWorkQueueException
{
if (queueId != 0)
throw new NoSuchWorkQueueException();
return workQueue;
}
/**
* To be called from the workqueue when work is added to the
* workQueue. This method would create new threads if required
* or notify waiting threads on the queue for available work
*/
void notifyForAvailableWork(WorkQueue aWorkQueue) {
synchronized (lock) {
if (availableWorkerThreads == 0) {
createWorkerThread();
} else {
aWorkQueue.notify();
}
}
}
/**
* To be called from the workqueue to create worker threads when none
* available.
*/
void createWorkerThread() {
synchronized (lock) {
final String name = getName() ;
if (boundedThreadPool) {
if (currentThreadCount < maxWorkerThreads) {
currentThreadCount++;
} else {
// REVIST - Need to create a thread to monitor the
// the state for deadlock i.e. all threads waiting for
// something which can be got from the item in the
// workqueue, but there is no thread available to
// process that work item - DEADLOCK !!
return;
}
} else {
currentThreadCount++;
}
// If we get here, we need to create a thread.
AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
// Thread creation needs to be in a doPrivileged block
// for two reasons:
// 1. The creation of a thread in a specific ThreadGroup
// is a privileged operation. Lack of a doPrivileged
// block here causes an AccessControlException
// (see bug 6268145).
// 2. We want to make sure that the permissions associated
// with this thread do NOT include the permissions of
// the current thread that is calling this method.
// This leads to problems in the app server where
// some threads in the ThreadPool randomly get
// bad permissions, leading to unpredictable
// permission errors.
WorkerThread thread = new WorkerThread(threadGroup, name);
// The thread must be set to a daemon thread so the
// VM can exit if the only threads left are PooledThreads
// or other daemons. We don't want to rely on the
// calling thread always being a daemon.
// Note that no exception is possible here since we
// are inside the doPrivileged block.
thread.setDaemon(true);
thread.start();
return null ;
}
}
) ;
}
}
/**
* This method will return the minimum number of threads maintained
* by the threadpool.
*/
public int minimumNumberOfThreads() {
return minWorkerThreads;
}
/**
* This method will return the maximum number of threads in the
* threadpool at any point in time, for the life of the threadpool
*/
public int maximumNumberOfThreads() {
return maxWorkerThreads;
}
/**
* This method will return the time in milliseconds when idle
* threads in the threadpool are removed.
*/
public long idleTimeoutForThreads() {
return inactivityTimeout;
}
/**
* This method will return the total number of threads currently in the
* threadpool. This method returns a value which is not synchronized.
*/
public int currentNumberOfThreads() {
synchronized (lock) {
return currentThreadCount;
}
}
/**
* This method will return the number of available threads in the
* threadpool which are waiting for work. This method returns a
* value which is not synchronized.
*/
public int numberOfAvailableThreads() {
synchronized (lock) {
return availableWorkerThreads;
}
}
/**
* This method will return the number of busy threads in the threadpool
* This method returns a value which is not synchronized.
*/
public int numberOfBusyThreads() {
synchronized (lock) {
return (currentThreadCount - availableWorkerThreads);
}
}
/**
* This method returns the average elapsed time taken to complete a Work
* item in milliseconds.
*/
public long averageWorkCompletionTime() {
synchronized (lock) {
return (totalTimeTaken / processedCount);
}
}
/**
* This method returns the number of Work items processed by the threadpool
*/
public long currentProcessedCount() {
synchronized (lock) {
return processedCount;
}
}
public String getName() {
return name;
}
/**
* This method will return the number of WorkQueues serviced by the threadpool.
*/
public int numberOfWorkQueues() {
return 1;
}
private static synchronized int getUniqueThreadId() {
return ThreadPoolImpl.threadCounter++;
}
private class WorkerThread extends Thread
{
private Work currentWork;
private int threadId = 0; // unique id for the thread
// thread pool this WorkerThread belongs too
private String threadPoolName;
// name seen by Thread.getName()
private StringBuffer workerThreadName = new StringBuffer();
WorkerThread(ThreadGroup tg, String threadPoolName) {
super(tg, "Idle");
this.threadId = ThreadPoolImpl.getUniqueThreadId();
this.threadPoolName = threadPoolName;
setName(composeWorkerThreadName(threadPoolName, "Idle"));
}
public void run() {
while (true) {
try {
synchronized (lock) {
availableWorkerThreads++;
}
// Get some work to do
currentWork = ((WorkQueueImpl)workQueue).requestWork(inactivityTimeout);
synchronized (lock) {
availableWorkerThreads--;
// It is possible in notifyForAvailableWork that the
// check for availableWorkerThreads = 0 may return
// false, because the availableWorkerThreads has not been
// decremented to zero before the producer thread added
// work to the queue. This may create a deadlock, if the
// executing thread needs information which is in the work
// item queued in the workqueue, but has no thread to work
// on it since none was created because availableWorkerThreads = 0
// returned false.
// The following code will ensure that a thread is always available
// in those situations
if ((availableWorkerThreads == 0) &&
(workQueue.workItemsInQueue() > 0)) {
createWorkerThread();
}
}
// Set the thread name for debugging.
setName(composeWorkerThreadName(threadPoolName,
Integer.toString(this.threadId)));
long start = System.currentTimeMillis();
try {
// Do the work
currentWork.doWork();
} catch (Throwable t) {
// Ignore all errors.
;
}
long end = System.currentTimeMillis();
synchronized (lock) {
totalTimeTaken += (end - start);
processedCount++;
}
// set currentWork to null so that the work item can be
// garbage collected
currentWork = null;
setName(composeWorkerThreadName(threadPoolName, "Idle"));
} catch (TimeoutException e) {
// This thread timed out waiting for something to do.
synchronized (lock) {
availableWorkerThreads--;
// This should for both bounded and unbounded case
if (currentThreadCount > minWorkerThreads) {
currentThreadCount--;
// This thread can exit.
return;
} else {
// Go back to waiting on workQueue
continue;
}
}
} catch (InterruptedException ie) {
// InterruptedExceptions are
// caught here. Thus, threads can be forced out of
// requestWork and so they have to reacquire the lock.
// Other options include ignoring or
// letting this thread die.
// Ignoring for now. REVISIT
synchronized (lock) {
availableWorkerThreads--;
}
} catch (Throwable e) {
// Ignore any exceptions that currentWork.process
// accidently lets through, but let Errors pass.
// Add debugging output? REVISIT
synchronized (lock) {
availableWorkerThreads--;
}
}
}
}
private String composeWorkerThreadName(String poolName, String workerName) {
workerThreadName.setLength(0);
workerThreadName.append("p: ").append(poolName);
workerThreadName.append("; w: ").append(workerName);
return workerThreadName.toString();
}
} // End of WorkerThread class
}
// End of file.
|
