undertow 怎麼建立線程_【線程池-ing】

一、線程池作用

1. 複用已有的資源，解決頻繁建立和銷毀線程帶來的開銷
2. 控制資源的總數，解決線程建立時數量不可控

優勢：

1. 可限流，控制線程數量
2. 降低頻繁建立和銷毀線程帶來的性能開銷
3. 對于任務響應速度更快

二、java中提供的線程池

jdk、spring

ThreadPoolExecutor執行個體

變量 ctl 32bit

高3位代表目前的線程池狀态

低29位代表目前的線程數量

command = new App() implement Runable;

addworker(command,true);

1.添加工作線程數(cas添加工作線程數量)

2.建立工作線程

Executors線程池工廠類實際調用重載的new ThreadPoolExecutor()構造方法

public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue,
                          ThreadFactory threadFactory,
                          RejectedExecutionHandler handler) {
    if (corePoolSize < 0 ||
        maximumPoolSize <= 0 ||
        maximumPoolSize < corePoolSize ||
        keepAliveTime < 0)
        throw new IllegalArgumentException();
    if (workQueue == null || threadFactory == null || handler == null)
        throw new NullPointerException();
    this.acc = System.getSecurityManager() == null ?
            null :
            AccessController.getContext();
    this.corePoolSize = corePoolSize;
    this.maximumPoolSize = maximumPoolSize;
    this.workQueue = workQueue;
    this.keepAliveTime = unit.toNanos(keepAliveTime);
    this.threadFactory = threadFactory;
    this.handler = handler;
}
           

1. 固定容量的線程池：Executors.newFixedThreadPool

return new ThreadPoolExecutor(nThreads, nThreads,
                              0L, TimeUnit.MILLISECONDS,
                              new LinkedBlockingQueue<Runnable>(),
                              threadFactory);
           

2. 定時/周期 定長的線程池：Executors. newScheduledThreadPool

return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
           

3. 建立一個可緩存線程池：Executors.newCachedThreadPool

return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                              60L, TimeUnit.SECONDS,
                              new SynchronousQueue<Runnable>());
           

4. 單線程化的線程池：Executors.newSingleThreadExecutor

return new FinalizableDelegatedExecutorService
    (new ThreadPoolExecutor(1, 1,
                            0L, TimeUnit.MILLISECONDS,
                            new LinkedBlockingQueue<Runnable>()));
           

問題：KeepaliveTime，怎麼去監控線程進行回收?

三、ThreadPoolExecutor構造參數

01核心線程數、02最大線程數、03活躍時間、

04活躍時間機關、05阻塞隊列：線程池超過核心線程數進隊列

06線程工廠執行個體、07拒絕政策Hander：線程池超過最大線程數且隊列滿了時會調用飽和政策