下面看下相关代码：
首先是队列这块，我们重点关注下重写的offer方法，返回false来增加线程的时机：
@Slf4j
public class TomcatTaskQueue extends LinkedBlockingQueue<Runnable> {
private transient volatile TomcatThreadPool parent = null;
public TomcatTaskQueue(int capacity) {
super(capacity);
}
public void setParent(TomcatThreadPool tp) {
parent = tp;
}
public boolean force(Runnable o) {
if (parent == null || parent.isShutdown())
throw new RejectedExecutionException("taskQueue.notRunning");
return super.offer(o); //forces the item onto the queue, to be used if the task is rejected
}
public boolean force(Runnable o, long timeout, TimeUnit unit) throws InterruptedException {
if (parent == null || parent.isShutdown())
throw new RejectedExecutionException("taskQueue.notRunning");
return super.offer(o, timeout, unit); //forces the item onto the queue, to be used if the task is rejected
}
@Override
public boolean offer(Runnable o) {
//we can't do any checks
if (parent == null)
return super.offer(o);
//we are maxed out on threads, simply queue the object
if (parent.getPoolSize() == parent.getMaximumPoolSize()) {
log.info("pool==max, getPoolSize: {}, getMaximumPoolSize:{}, task:{}", parent.getPoolSize(), parent.getMaximumPoolSize(), o);
return super.offer(o);
}
//we have idle threads, just add it to the queue
if (parent.getSubmittedCount() <= (parent.getPoolSize())) {
log.info("submit<=pool, getPoolSize: {}, getMaximumPoolSize:{}, task:{}", parent.getPoolSize(), parent.getMaximumPoolSize(), o);
return super.offer(o);
}
//if we have less threads than maximum force creation of a new thread
if (parent.getPoolSize() < parent.getMaximumPoolSize()) {
log.info("Grow thread pool, getPoolSize: {}, getMaximumPoolSize:{}", parent.getPoolSize(), parent.getMaximumPoolSize());
return false;
}
//if we reached here, we need to add it to the queue
log.info("else, getPoolSize: {}, getMaximumPoolSize:{}, task:{}", parent.getPoolSize(), parent.getMaximumPoolSize(), o);
return super.offer(o);
}
