Java 更改线程池执行器
如以下链接所述:- 我将队列实现更改为在输入元素后返回false。 因此,每当将新任务插入队列时,都会为其创建一个新线程 但是,当我大规模运行下面的实现(Bis系统测试)时,日志记录者遇到了一个新问题 当一个任务来执行时,它会被插入到队列中,当队列返回false时,会创建一个新线程来执行它。不会拾取池中当前存在的空闲线程。原因是任务从从从队列中拾取任务的Java 更改线程池执行器,java,multithreading,java.util.concurrent,threadpoolexecutor,Java,Multithreading,Java.util.concurrent,Threadpoolexecutor,如以下链接所述:- 我将队列实现更改为在输入元素后返回false。 因此,每当将新任务插入队列时,都会为其创建一个新线程 但是,当我大规模运行下面的实现(Bis系统测试)时,日志记录者遇到了一个新问题 当一个任务来执行时,它会被插入到队列中,当队列返回false时,会创建一个新线程来执行它。不会拾取池中当前存在的空闲线程。原因是任务从从从队列中拾取任务的getTask()方法分配给空闲线程。因此,我的问题是如何更改此行为,以便在线程空闲时如何确保为空闲线程分配执行任务,而不是创建新线程???
getTask()
方法分配给空闲线程。因此,我的问题是如何更改此行为,以便在线程空闲时如何确保为空闲线程分配执行任务,而不是创建新线程???
下面的输出将更加清楚:-
Task 46 ends
Active Count: 0 Pool Size : 3 Idle Count: 3 Queue Size: 0
Task 47 ends
Active Count: 0 Pool Size : 3 Idle Count: 3 Queue Size: 0
Task 48 ends
Active Count: 0 Pool Size : 3 Idle Count: 3 Queue Size: 0
Active Count: 1 Pool Size : 4 Idle Count: 3 Queue Size: 0
Task 49 ends
Active Count: 2 Pool Size : 5 Idle Count: 3 Queue Size: 0
Task 50 ends
Active Count: 2 Pool Size : 5 Idle Count: 3 Queue Size: 0
代码文件如下所示:-
ThreadPoolExecutor是java 1.5版本,因为我们在服务器计算机上使用1.5,无法升级
线程池执行器:-
public void execute(Runnable command) {
System.out.println("Active Count: " + getActiveCount()
+ " Pool Size : " + getPoolSize() + " Idle Count: "
+ (getPoolSize() - getActiveCount())+" Queue Size: "+getQueue().size());
if (command == null)
throw new NullPointerException();
for (;;) {
if (runState != RUNNING) {
reject(command);
return;
}
if (poolSize < corePoolSize && addIfUnderCorePoolSize(command))
return;
if (workQueue.offer(command))
return;
int status = addIfUnderMaximumPoolSize(command);
if (status > 0) // created new thread
return;
if (status == 0) { // failed to create thread
reject(command);
return;
}
// Retry if created a new thread but it is busy with another task
}
}
public class CustomBlockingQueue<E> extends LinkedBlockingQueue<E>
{
/**
*
*/
private static final long serialVersionUID = 1L;
public CustomBlockingQueue() {
super(Integer.MAX_VALUE);
}
public boolean offer(E e) {
return false;
}
}
public void execute(Runnable命令){
System.out.println(“活动计数:”+getActiveCount()
+池大小:“+getPoolSize()+”空闲计数:
+(getPoolSize()-getActiveCount())+“队列大小:”+getQueue().Size());
如果(命令==null)
抛出新的NullPointerException();
对于(;;){
如果(运行状态!=正在运行){
拒绝(命令);
返回;
}
if(poolSize0)//已创建新线程
返回;
如果(状态==0){//创建线程失败
拒绝(命令);
返回;
}
//如果创建了一个新线程,但它正忙于另一个任务,请重试
}
}
LinkedBlockingQueue:-
public void execute(Runnable command) {
System.out.println("Active Count: " + getActiveCount()
+ " Pool Size : " + getPoolSize() + " Idle Count: "
+ (getPoolSize() - getActiveCount())+" Queue Size: "+getQueue().size());
if (command == null)
throw new NullPointerException();
for (;;) {
if (runState != RUNNING) {
reject(command);
return;
}
if (poolSize < corePoolSize && addIfUnderCorePoolSize(command))
return;
if (workQueue.offer(command))
return;
int status = addIfUnderMaximumPoolSize(command);
if (status > 0) // created new thread
return;
if (status == 0) { // failed to create thread
reject(command);
return;
}
// Retry if created a new thread but it is busy with another task
}
}
public class CustomBlockingQueue<E> extends LinkedBlockingQueue<E>
{
/**
*
*/
private static final long serialVersionUID = 1L;
public CustomBlockingQueue() {
super(Integer.MAX_VALUE);
}
public boolean offer(E e) {
return false;
}
}
公共类CustomBlockingQueue扩展LinkedBlockingQueue
{
/**
*
*/
私有静态最终长serialVersionUID=1L;
公共CustomBlockingQueue(){
super(整数最大值);
}
公共布尔报价(E){
返回false;
}
}
在拒绝处理程序中,我们正在调用队列的put方法,但尚未覆盖该方法
呼叫执行器
final CustomThreadPoolExecutor tpe = new CustomThreadPoolExecutor(3, 8, 0L, TimeUnit.MILLISECONDS, new MediationBlockingQueue<Runnable>(), new MediationRejectionHandler());
private static final int TASK_COUNT = 100;
for (int i = 0; i < TASK_COUNT; i++) {
......
tpe.execute(new Task(i));
.....
}
final CustomThreadPoolExecutor tpe=new CustomThreadPoolExecutor(3,8,0L,TimeUnit.ms,new MediationBlockingQueue(),new MediationRejectionHandler());
私有静态最终整数任务计数=100;
对于(int i=0;i
我们正在调用执行器,核心池大小为3,最大池大小为8,并为任务使用无界链接阻塞队列 实现“先启动后排队,但更喜欢现有线程”行为的最简单方法是使用。当且仅当已经有等待的接收者时,它才会接受提供的物品。因此,空闲线程将获取项目,一旦没有空闲线程,
ThreadPoolExecutor
将启动新线程
唯一的缺点是,一旦启动了所有线程,就不能简单地将挂起的项放入队列,因为它没有容量。因此,您要么必须接受提交者被阻止,要么需要另一个队列将挂起的任务放入其中,或者需要另一个后台线程将这些挂起的项目放入同步队列。这个额外的线程不会影响性能,因为它大部分时间都被阻塞在这两个队列中
class QueuingRejectionHandler implements RejectedExecutionHandler {
final ExecutorService processPending=Executors.newSingleThreadExecutor();
public void rejectedExecution(
final Runnable r, final ThreadPoolExecutor executor) {
processPending.execute(new Runnable() {
public void run() {
executor.execute(r);
}
});
}
}
ThreadPoolExecutor e=新的ThreadPoolExecutor(
corePoolSize、maximumPoolSize、keepAliveTime、单位、,
新建SynchronousQueue(),新建QueuingRejectionHandler());
格雷给出的解决方案非常棒,但我遇到了和你一样的问题,也就是说,理想线程并没有被用来选择新任务,但新线程是在poolSize小于maxPoolSize的情况下创建的
所以,我试图调整ThreadPoolExecutor本身的功能,通过复制完整的类(这不是一个好主意,但找不到任何其他解决方案),并使用ThreadPoolExecutor扩展它并重写execute方法
方法如下:
public void execute(Runnable command)
{
System.out.println("ActiveCount : " + this.getActiveCount()
+ " PoolSize : " + this.getPoolSize() + " QueueSize : "
+ this.getQueue().size());
if (command == null)
throw new NullPointerException();
for (;;)
{
if (runState != RUNNING)
{
reject(command);
return;
}
if (poolSize < corePoolSize && addIfUnderCorePoolSize(command))
return;
//Now, it will never offer to queue but will go further for thread creation.
//if (workQueue.offer(command))
//return;
//This check is introduced to utilized ideal threads instead of creating new thread
//for incoming tasks.
//Example : coreSize = 3, maxPoolSize = 8.
//activeCount = 4, and PoolSize = 5, so 1 thread is ideal Currently queue is empty.
//When new task comes, it will offer that to queue, and getTask() will take care and execute the task.
//But if new task comes, before ideal thread takes task from queue,
//activeCount = 4, and PoolSize = 5, so 1 thread is ideal Currently queue size = 1.
//this check fails and new thread is created if poolsize under max size or
//task is added to queue through rejection handler.
if ((this.getPoolSize() - this.getActiveCount()) > 0 &&
(this.getPoolSize() - this.getActiveCount() - workQueue.size()) > 0)
{
workQueue.offer(command);
return;
}
int status = addIfUnderMaximumPoolSize(command);
if (status > 0) // created new thread
return;
if (status == 0)
{ // failed to create thread
reject(command);
return;
}
// Retry if created a new thread but it is busy with another task
}
}
public void execute(Runnable命令)
{
System.out.println(“ActiveCount:+this.getActiveCount()
+PoolSize:“+this.getPoolSize()+”队列大小:
+这个.getQueue().size());
如果(命令==null)
抛出新的NullPointerException();
对于(;;)
{
如果(运行状态!=正在运行)
{
拒绝(命令);
返回;
}
if(poolSize0&&
(this.getPoolSize()-this.getActiveCount()-workQueue.size())>0)
{
workQueue.offer(命令);
返回;
}
int status=addIfUnderMaximumPoolSize(命令);
public boolean offer(Runnable e) {
/*
* Offer it to the queue if there is 1 or 0 items already queued, else
* return false so the TPE will add another thread.
*/
if (size() <= 1) {
return super.offer(e);
} else {
return false;
}
}
public static ExecutorService newWorkStealingPool()
ExecutorService executorService = Executors.newWorkStealingPool();