import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Created by yehan .
* 代码和思路主要来自于：
*
* tomcat :
* org.apache.catalina.core.StandardThreadExecutor
*
* java.util.concurrent
* threadPoolExecutor execute执行策略： 优先offer到queue，queue满后再扩充线程到maxThread，如果已经到了maxThread就reject
* 比较适合于CPU密集型应用（比如runnable内部执行的操作都在JVM内部，memory copy, or compute等等）
*
* StandardThreadExecutor execute执行策略： 优先扩充线程到maxThread，再offer到queue，如果满了就reject
* 比较适合于业务处理需要远程资源的场景
*
* @author yehan
*
*/
public class StandardThreadExecutorextends ThreadPoolExecutor {
public static final int DEFAULT_MIN_THREADS =20;
public static final int DEFAULT_MAX_THREADS =200;
/**1 minutes*/
public static final int DEFAULT_MAX_IDLE_TIME =60 *1000;
/**正在处理的任务数*/
protected AtomicIntegersubmittedTasksCount;
/**最大允许同时处理的任务数*/
private int maxSubmittedTaskCount;
public StandardThreadExecutor() {
this(DEFAULT_MIN_THREADS, DEFAULT_MAX_THREADS);
}
public StandardThreadExecutor(int coreThread, int maxThreads) {
this(coreThread, maxThreads, maxThreads);
}
public StandardThreadExecutor(int coreThread, int maxThreads, long keepAliveTime, TimeUnit unit) {
this(coreThread, maxThreads, keepAliveTime, unit, maxThreads);
}
public StandardThreadExecutor(int coreThreads, int maxThreads, int queueCapacity) {
this(coreThreads, maxThreads, queueCapacity, Executors.defaultThreadFactory());
}
public StandardThreadExecutor(int coreThreads, int maxThreads, int queueCapacity, ThreadFactory threadFactory) {
this(coreThreads, maxThreads, DEFAULT_MAX_IDLE_TIME, TimeUnit.MILLISECONDS, queueCapacity, threadFactory);
}
public StandardThreadExecutor(int coreThreads, int maxThreads, long keepAliveTime, TimeUnit unit, int queueCapacity) {
this(coreThreads, maxThreads, keepAliveTime, unit, queueCapacity, Executors.defaultThreadFactory());
}
public StandardThreadExecutor(int coreThreads, int maxThreads, long keepAliveTime, TimeUnit unit,
int queueCapacity, ThreadFactory threadFactory) {
this(coreThreads, maxThreads, keepAliveTime, unit, queueCapacity, threadFactory, new AbortPolicy());
}
public StandardThreadExecutor(int coreThreads, int maxThreads, long keepAliveTime, TimeUnit unit,
int queueCapacity, ThreadFactory threadFactory, RejectedExecutionHandler handler) {
super(coreThreads, maxThreads, keepAliveTime, unit, new ExecutorQueue(), threadFactory, handler);
((ExecutorQueue) getQueue()).setStandardThreadExecutor(this);
submittedTasksCount =new AtomicInteger(0);
// 最大并发任务限制： 队列buffer数 + 最大线程数
maxSubmittedTaskCount = queueCapacity + maxThreads;
}
@Override
public void execute(Runnable command) {
int count =submittedTasksCount.incrementAndGet();
// 超过最大的并发任务限制，进行 reject
// 依赖的LinkedTransferQueue没有长度限制，因此这里进行控制
if (count >maxSubmittedTaskCount) {
submittedTasksCount.decrementAndGet();
getRejectedExecutionHandler().rejectedExecution(command, this);
}
try {
super.execute(command);
}catch (RejectedExecutionException rx) {
// there could have been contention around the queue
if (!((ExecutorQueue) getQueue()).force(command)) {
submittedTasksCount.decrementAndGet();
getRejectedExecutionHandler().rejectedExecution(command, this);
}
}
}
public int getSubmittedTasksCount() {
return this.submittedTasksCount.get();
}
public int getMaxSubmittedTaskCount() {
return maxSubmittedTaskCount;
}
@Override
protected void afterExecute(Runnable r, Throwable t) {
submittedTasksCount.decrementAndGet();
}
}
/**
* LinkedTransferQueue 能保证更高性能，相比与LinkedBlockingQueue有明显提升
*
*
* 1) 不过LinkedTransferQueue的缺点是没有队列长度控制，需要在外层协助控制
*
*
* @author yehan
*
*/
class ExecutorQueueextends LinkedTransferQueue {
private static final long serialVersionUID = -265236426751004839L;
StandardThreadExecutorthreadPoolExecutor;
public ExecutorQueue() {
super();
}
public void setStandardThreadExecutor(StandardThreadExecutor threadPoolExecutor) {
this.threadPoolExecutor = threadPoolExecutor;
}
/** 注：代码来源于 tomcat*/
public boolean force(Runnable o) {
if (threadPoolExecutor.isShutdown()) {
throw new RejectedExecutionException("Executor not running, can't force a command into the queue");
}
// forces the item onto the queue, to be used if the task is rejected
return super.offer(o);
}
/**
*注：tomcat的代码进行一些小变更
*
*/
@Override
public boolean offer(Runnable o) {
int poolSize =threadPoolExecutor.getPoolSize();
// we are maxed out on threads, simply queue the object
if (poolSize ==threadPoolExecutor.getMaximumPoolSize()) {
return super.offer(o);
}
// we have idle threads, just add it to the queue
// note that we don't use getActiveCount(), see BZ 49730
if (threadPoolExecutor.getSubmittedTasksCount() <= poolSize) {
return super.offer(o);
}
// if we have less threads than maximum force creation of a new
// thread
if (poolSize
return false;
}
// if we reached here, we need to add it to the queue
return super.offer(o);
}
}
