基于Spring Boot的线程池监控方案

前言

这篇是推动大家异步编程的思想的线程池的准备篇，要做好监控，让大家使用无后顾之忧，敬畏生产。

为什么需要对线程池进行监控

Java线程池作为最常使用到的并发工具，相信大家都不陌生，但是你真的确定使用对了吗？大名鼎鼎的阿里Java代码规范要求我们不使用 Executors来快速创建线程池，但是抛弃Executors，使用其它方式创建线程池就一定不会出现问题吗？本质上对于我们来说线程池本身的运行过程是一个黑盒，我们没办法了解线程池中的运行状态时，出现问题没有办法及时判断和预警。面对这种黑盒操作必须通过监控方式让其透明化，这样对我们来说才能更好的使用好线程池。因此必须对线程池做监控。

如何做线程池的监控

对于如何做监控，本质就是涉及三点，分别是数据采集、数据存储以及大盘的展示，接下来我们分说下这三点；

数据采集

采集什么数据，对于我们来说需要采集就是黑盒的数据，什么又是线程池的黑盒数据，其实也就是整个线程处理的整个流程，在整个流程中，我们可以通过ThreadPoolExecutor中的七个方法获取数据，通过这七个方法采集到的数据就可以使线程池的执行过程透明化。

getCorePoolSize()：获取核心线程数；getMaximumPoolSize：获取最大线程数；getQueue()：获取线程池中的阻塞队列，并通过阻塞队列中的方法获取队列长度、元素个数等；getPoolSize()：获取线程池中的工作线程数（包括核心线程和非核心线程）；getActiveCount()：获取活跃线程数，也就是正在执行任务的线程；getLargestPoolSize()：获取线程池曾经到过的最大工作线程数；getTaskCount()：获取历史已完成以及正在执行的总的任务数量；

除了我们了解的这些流程以外，ThreadPoolExecutor中还提供了三种钩子函数，

beforeExecute()：Worker线程执行任务之前会调用的方法；afterExecute()：在Worker线程执行任务之后会调用的方法；terminated()：当线程池从运行状态变更到TERMINATED状态之前调用的方法;

对于beforeExecute和afterExecute可以理解为使用Aop监听线程执行的时间，这样子我们可以对每个线程运行的时间整体做监控，terminated可以理解为线程关闭时候的监控，这样我们就可以整体获取采集到线程池生命周期的所有数据了。

数据存储以及大盘的展示

对于存储我们这个比较适合采用时序性数据库，此外现在很多成熟的监控产品都可以满足我们大屏展示的诉求，这里推荐下美团Cat和Prometheus，这里不展开进行讲解，大家可以根据自己公司的监控产品进行选择，对于不同的方案采取的存储形式会有些差异，甚至自己都可以自定义实现一个功能，反正难度不大。

进一步扩展以及思考

在实际的项目开发中我们会遇到以下场景:

不同的业务采用同一个线程池，这样如果某个服务阻塞，会影响到整体共用线程池的所有服务，会触发线程池的拒绝策略；流量突然增加，需要动态调整线程池的参数，这个时候又不能重启；

针对这两种场景，我们对线程池再次进行了深入的思考:

如何合理配置线程池参数；如何动态调整线程池参数；如何给不同的服务之间做线程池的隔离；如何合理配置线程池参数

关于这个问题面试的时候也是经常被问到，我只能说这个问题开始就是一个坑，针对与CPU密集型和I/O密集型，线程池的参数是有不同设计的，也不是遵守几个公式就可以搞定，当然可以参考，我认为对于线程池合理的参数的配置是经过多次调整得到的，甚至增加和减少业务都会影响一些参数，我不太建议大家每天背书式的CPU密集型就是N+1，非CPU密集型就是2N，因此我们更希望看到线程池动态配置。

如何动态调整线程池参数

关于如何动态调整线程池，还是回到我们场景问题的解决上，对于流量突增核心就是提升线程池的处理速度，那如何提升线程池的处理速度，有两种方式，一种是加快业务的处理，也就是消费的快，显然这种在运行的业务中我们想改变还是比较困难，这个可以作为复盘的重点；还有一种就是增加消费者，增加消费者的重点就是调整核心线程数以及非核心线程数的数量。

居于这种思考，这个时候我们需要看下ThreadPoolExecutor线程池源码，首先看下开始定义的变量，通过变量的设计我们就会发现大师就是大师，大师通过AtomicInteger修饰的ctl变量，高3位存储了线程池的状态，低29存储线程的个数，通过一个变量完成两件事情，完成状态判断以及限制线程最大个数。使用一个HashSet存储Worker的引用，而Worker继承了AbstractQueuedSynchronizer，实现一个一个不可冲入的独占锁保证线程的安全性。

//用来标记线程池状态（高3位），线程个数（低29位）     
private final AtomicInteger ctl = new AtomicInteger(ctlOf(RUNNING, 0));
//工作状态存储在高3位中
private static final int COUNT_BITS = Integer.SIZE - 3;
//线程个数所能表达的最大数值
private static final int CAPACITY   = (1 << COUNT_BITS) - 1;
//线程池状态
//RUNNING -1 能够接收新任务，也可以处理阻塞队列中的任务
private static final int RUNNING    = -1 << COUNT_BITS;
//SHUTDOWN 0 不可以接受新任务，继续处理阻塞队列中的任务
private static final int SHUTDOWN   =  0 << COUNT_BITS;
//STOP 1 不接收新任务，不处理阻塞队列中的任务，并且会中断正在处理的任务
private static final int STOP       =  1 << COUNT_BITS;
//TIDYING 2 所有任务已经中止，且工作线程数量为0，最后变迁到这个状态的线程将要执行terminated()钩子方法，只会有一个线程执行这个方法；
private static final int TIDYING    =  2 << COUNT_BITS;
//TERMINATED 3 中止状态，已经执行完terminated()钩子方法
private static final int TERMINATED =  3 << COUNT_BITS;
//任务队列，当线程池中的线程达到核心线程数量时，再提交任务 就会直接提交到 workQueue
private final BlockingQueue workQueue;
//线程池全局锁，增加worker减少worker时需要持有mainLock，修改线程池运行状态时，也需要
private final ReentrantLock mainLock = new ReentrantLock();
//线程池中真正存放worker的地方。
private final HashSet workers = new HashSet();
private final Condition termination = mainLock.newCondition();
//记录线程池生命周期内 线程数最大值
private int largestPoolSize;
//记录线程池所完成任务总数
private long completedTaskCount;
//创建线程会使用线程工厂
private volatile ThreadFactory threadFactory;
//拒绝策略
private volatile RejectedExecutionHandler handler;
//存活时间
private volatile long keepAliveTime;
//控制核心线程数量内的线程 是否可以被回收。true 可以，false不可以。
private volatile boolean allowCoreThreadTimeOut;
//核心线程池数量
private volatile int corePoolSize;
//线程池最大数量
private volatile int maximumPoolSize;

我们的重点看的是volatile修饰的corePoolSize、maximumPoolSize以及keepAliveTime，当然threadFactory和handler也可以看下，不过这两个不是我们解决动态调整线程池的关键。对于这些volatile修饰的关键的变量，从并发角度思考的，必然是有并发读写的操作才使用volatile修饰的，在指标采集中我们看到其get***的方法，对于写的操作我们可以猜测肯定提供了set***的方式，这个时候我们可以搜索下setCorePoolSize，果不其然我们真的搜索到了。

    public void setCorePoolSize(int corePoolSize) {
        if (corePoolSize < 0)
            throw new IllegalArgumentException();
        int delta = corePoolSize - this.corePoolSize;
        this.corePoolSize = corePoolSize;
        //新设置的corePoolSize小于当前核心线程数的时候
        //会调用interruptIdleWorkers方法来中断空闲的工作线程
        if (workerCountOf(ctl.get()) > corePoolSize)
            interruptIdleWorkers();
        else if (delta > 0) {
            //当设置的值大于当前值的时候核心线程数的时候
            //按照等待队列中的任务数量来创建新的工作线程
            int k = Math.min(delta, workQueue.size());
            while (k-- > 0 && addWorker(null, true)) {
                if (workQueue.isEmpty())
                    break;
            }
        }
    }

接下来我们看下interruptIdleWorkers的源码，此处源码使用ReentrantLock可重入锁，因为Worker的是通过一个全局的HashSer存储，这里通过ReentrantLock保证线程安全。

    private void interruptIdleWorkers(boolean onlyOne) {
        //可重入锁
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            for (Worker w : workers) {
                Thread t = w.thread;
                if (!t.isInterrupted() && w.tryLock()) {
                    try {
                        //中断当前线程
                        t.interrupt();
                    } catch (SecurityException ignore) {
                    } finally {
                        w.unlock();
                    }
                }
                if (onlyOne)
                    break;
            }
        } finally {
            mainLock.unlock();
        }
    }

接下来我们在验证一下是否存在其他相关的参数设置，如下：

    public void setMaximumPoolSize(int maximumPoolSize) {
        if (maximumPoolSize <= 0 || maximumPoolSize < corePoolSize)
            throw new IllegalArgumentException();
        this.maximumPoolSize = maximumPoolSize;
        if (workerCountOf(ctl.get()) > maximumPoolSize)
            interruptIdleWorkers();
    }
    public void setKeepAliveTime(long time, TimeUnit unit) {
        if (time < 0)
            throw new IllegalArgumentException();
        if (time == 0 && allowsCoreThreadTimeOut())
            throw new IllegalArgumentException("Core threads must have nonzero keep alive times");
        long keepAliveTime = unit.toNanos(time);
        long delta = keepAliveTime - this.keepAliveTime;
        this.keepAliveTime = keepAliveTime;
        if (delta < 0)
            interruptIdleWorkers();
    }
    public void setRejectedExecutionHandler(RejectedExecutionHandler handler) {
        if (handler == null)
            throw new NullPointerException();
        this.handler = handler;
    }

这里我们会发现一个问题BlockingQueue的队列容量不能修改，看到美团的文章提供的一个可修改的队列ResizableCapacitylinkedBlockingQueue，于是乎去看了一下linkedBlockingQueue的源码，发现了关于capacity是一个final修饰的，这个时候我就思考一番，这个地方采用volatile修饰，对外暴露可修改，这样就实现了动态修改阻塞队列的大小。

如何给不同的服务之间做线程池的隔离

关于如何给不同服务之间做线程池的隔离，这里我们可以采用Hystrix的舱壁模式，也就是说针对不同服务类型的服务单独创建线程池，这样就可以实现服务之间不相互影响，不会因为某个服务导致整体的服务影响都阻塞。

实现方案

聊了这么多前置的知识储备，接下来我们来聊聊实现方案，整体的实现方案我们建立在Spring Boot的基础实现，采用Spring Cloud刷新动态配置，采用该方式比较合适单体应用，对于有Appllo和Nacos可以通过监听配置方式的来动态刷新。

Maven依赖如下；

    
        
            org.springframework.boot
            spring-boot-starter
        
        
            org.springframework.boot
            spring-boot-starter-web
        
        
            org.springframework.cloud
            spring-cloud-context
        
        
            org.springframework.boot
            spring-boot-starter-test
            test
        
        
            org.projectlombok
            lombok
            1.18.12
        
        
            org.slf4j
            slf4j-api
            1.7.5
        
        
            ch.qos.logback
            logback-core
            1.2.3
        
        
            ch.qos.logback
            logback-classic
            1.2.3
        

    

    
        
            
                org.springframework.cloud
                spring-cloud-dependencies
                Hoxton.SR7
                pom
                import

配置信息如下:

monitor.threadpool.executors[0].thread-pool-name=first-monitor-thread-pool
monitor.threadpool.executors[0].core-pool-size=4
monitor.threadpool.executors[0].max-pool-size=8
monitor.threadpool.executors[0].queue-capacity=100

monitor.threadpool.executors[1].thread-pool-name=second-monitor-thread-pool
monitor.threadpool.executors[1].core-pool-size=2
monitor.threadpool.executors[1].max-pool-size=4
monitor.threadpool.executors[1].queue-capacity=40
    

@Data
public class ThreadPoolProperties {

    
    private String threadPoolName;

    
    private Integer corePoolSize = Runtime.getRuntime().availableProcessors();

    
    private Integer maxPoolSize;

    
    private Integer queueCapacity;

    
    private String rejectedExecutionType = "AbortPolicy";

    
    private Long keepAliveTime = 1L;

    
    private TimeUnit unit = TimeUnit.MILLISECONDS;


}



@ConfigurationProperties(prefix = "monitor.threadpool")
@Data
@Component
public class DynamicThreadPoolProperties {

    private List executors;
}

自定可修改阻塞队列大小的方式如下:

public class ResizableCapacitylinkedBlockingQueue extends AbstractQueue
        implements BlockingDeque, java.io.Serializable {
    

    

    private static final long serialVersionUID = -387911632671998426L;

    
    static final class Node {
        
        E item;

        
        Node prev;

        
        Node next;

        Node(E x) {
            item = x;
        }
    }

    
    transient Node first;

    
    transient Node last;

    
    private transient int count;

    
    private volatile int capacity;

    public int getCapacity() {
        return capacity;
    }

    public void setCapacity(int capacity) {
        this.capacity = capacity;
    }

    
    final ReentrantLock lock = new ReentrantLock();

    
    private final Condition notEmpty = lock.newCondition();

    
    private final Condition notFull = lock.newCondition();

    
    public ResizableCapacitylinkedBlockingQueue() {
        this(Integer.MAX_VALUE);
    }

    
    public ResizableCapacitylinkedBlockingQueue(int capacity) {
        if (capacity <= 0) {
            throw new IllegalArgumentException();
        }
        this.capacity = capacity;
    }

    
    public ResizableCapacitylinkedBlockingQueue(Collection c) {
        this(Integer.MAX_VALUE);
        final ReentrantLock lock = this.lock;
        lock.lock(); // Never contended, but necessary for visibility
        try {
            for (E e : c) {
                if (e == null) {
                    throw new NullPointerException();
                }
                if (!linkLast(new Node(e))) {
                    throw new IllegalStateException("Deque full");
                }
            }
        } finally {
            lock.unlock();
        }
    }


    // Basic linking and unlinking operations, called only while holding lock

    
    private boolean linkFirst(Node node) {
        // assert lock.isHeldByCurrentThread();
        if (count >= capacity) {
            return false;
        }
        Node f = first;
        node.next = f;
        first = node;
        if (last == null) {
            last = node;
        } else {
            f.prev = node;
        }
        ++count;
        notEmpty.signal();
        return true;
    }

    
    private boolean linkLast(Node node) {
        // assert lock.isHeldByCurrentThread();
        if (count >= capacity) {
            return false;
        }
        Node l = last;
        node.prev = l;
        last = node;
        if (first == null) {
            first = node;
        } else {
            l.next = node;
        }
        ++count;
        notEmpty.signal();
        return true;
    }

    
    private E unlinkFirst() {
        // assert lock.isHeldByCurrentThread();
        Node f = first;
        if (f == null) {
            return null;
        }
        Node n = f.next;
        E item = f.item;
        f.item = null;
        f.next = f; // help GC
        first = n;
        if (n == null) {
            last = null;
        } else {
            n.prev = null;
        }
        --count;
        notFull.signal();
        return item;
    }

    
    private E unlinkLast() {
        // assert lock.isHeldByCurrentThread();
        Node l = last;
        if (l == null) {
            return null;
        }
        Node p = l.prev;
        E item = l.item;
        l.item = null;
        l.prev = l; // help GC
        last = p;
        if (p == null) {
            first = null;
        } else {
            p.next = null;
        }
        --count;
        notFull.signal();
        return item;
    }

    
    void unlink(Node x) {
        // assert lock.isHeldByCurrentThread();
        Node p = x.prev;
        Node n = x.next;
        if (p == null) {
            unlinkFirst();
        } else if (n == null) {
            unlinkLast();
        } else {
            p.next = n;
            n.prev = p;
            x.item = null;
            // Don't mess with x's links.  They may still be in use by
            // an iterator.
            --count;
            notFull.signal();
        }
    }

    // BlockingDeque methods

    
    @Override
    public void addFirst(E e) {
        if (!offerFirst(e)) {
            throw new IllegalStateException("Deque full");
        }
    }

    
    @Override
    public void addLast(E e) {
        if (!offerLast(e)) {
            throw new IllegalStateException("Deque full");
        }
    }

    
    @Override
    public boolean offerFirst(E e) {
        if (e == null) {
            throw new NullPointerException();
        }
        Node node = new Node(e);
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return linkFirst(node);
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public boolean offerLast(E e) {
        if (e == null) throw new NullPointerException();
        Node node = new Node(e);
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return linkLast(node);
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public void putFirst(E e) throws InterruptedException {
        if (e == null) {
            throw new NullPointerException();
        }
        Node node = new Node(e);
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            while (!linkFirst(node)) {
                notFull.await();
            }
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public void putLast(E e) throws InterruptedException {
        if (e == null) {
            throw new NullPointerException();
        }
        Node node = new Node(e);
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            while (!linkLast(node)) {
                notFull.await();
            }
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public boolean offerFirst(E e, long timeout, TimeUnit unit)
            throws InterruptedException {
        if (e == null) {
            throw new NullPointerException();
        }
        Node node = new Node(e);
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            while (!linkFirst(node)) {
                if (nanos <= 0) {
                    return false;
                }
                nanos = notFull.awaitNanos(nanos);
            }
            return true;
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public boolean offerLast(E e, long timeout, TimeUnit unit)
            throws InterruptedException {
        if (e == null) throw new NullPointerException();
        Node node = new Node(e);
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            while (!linkLast(node)) {
                if (nanos <= 0) {
                    return false;
                }
                nanos = notFull.awaitNanos(nanos);
            }
            return true;
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public E removeFirst() {
        E x = pollFirst();
        if (x == null) {
            throw new NoSuchElementException();
        }
        return x;
    }

    
    @Override
    public E removeLast() {
        E x = pollLast();
        if (x == null) {
            throw new NoSuchElementException();
        }
        return x;
    }

    @Override
    public E pollFirst() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return unlinkFirst();
        } finally {
            lock.unlock();
        }
    }

    @Override
    public E pollLast() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return unlinkLast();
        } finally {
            lock.unlock();
        }
    }

    @Override
    public E takeFirst() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            E x;
            while ((x = unlinkFirst()) == null) {
                notEmpty.await();
            }
            return x;
        } finally {
            lock.unlock();
        }
    }

    @Override
    public E takeLast() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            E x;
            while ((x = unlinkLast()) == null) {
                notEmpty.await();
            }
            return x;
        } finally {
            lock.unlock();
        }
    }

    @Override
    public E pollFirst(long timeout, TimeUnit unit)
            throws InterruptedException {
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            E x;
            while ((x = unlinkFirst()) == null) {
                if (nanos <= 0) {
                    return null;
                }
                nanos = notEmpty.awaitNanos(nanos);
            }
            return x;
        } finally {
            lock.unlock();
        }
    }

    @Override
    public E pollLast(long timeout, TimeUnit unit)
            throws InterruptedException {
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            E x;
            while ((x = unlinkLast()) == null) {
                if (nanos <= 0) {
                    return null;
                }
                nanos = notEmpty.awaitNanos(nanos);
            }
            return x;
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public E getFirst() {
        E x = peekFirst();
        if (x == null) {
            throw new NoSuchElementException();
        }
        return x;
    }

    
    @Override
    public E getLast() {
        E x = peekLast();
        if (x == null) {
            throw new NoSuchElementException();
        }
        return x;
    }

    @Override
    public E peekFirst() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return (first == null) ? null : first.item;
        } finally {
            lock.unlock();
        }
    }

    @Override
    public E peekLast() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return (last == null) ? null : last.item;
        } finally {
            lock.unlock();
        }
    }

    @Override
    public boolean removeFirstOccurrence(Object o) {
        if (o == null) {
            return false;
        }
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            for (Node p = first; p != null; p = p.next) {
                if (o.equals(p.item)) {
                    unlink(p);
                    return true;
                }
            }
            return false;
        } finally {
            lock.unlock();
        }
    }

    @Override
    public boolean removeLastOccurrence(Object o) {
        if (o == null) {
            return false;
        }
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            for (Node p = last; p != null; p = p.prev) {
                if (o.equals(p.item)) {
                    unlink(p);
                    return true;
                }
            }
            return false;
        } finally {
            lock.unlock();
        }
    }

    // BlockingQueue methods

    
    @Override
    public boolean add(E e) {
        addLast(e);
        return true;
    }

    
    @Override
    public boolean offer(E e) {
        return offerLast(e);
    }

    
    @Override
    public void put(E e) throws InterruptedException {
        putLast(e);
    }

    
    @Override
    public boolean offer(E e, long timeout, TimeUnit unit)
            throws InterruptedException {
        return offerLast(e, timeout, unit);
    }

    
    @Override
    public E remove() {
        return removeFirst();
    }

    @Override
    public E poll() {
        return pollFirst();
    }

    @Override
    public E take() throws InterruptedException {
        return takeFirst();
    }

    @Override
    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
        return pollFirst(timeout, unit);
    }

    
    @Override
    public E element() {
        return getFirst();
    }

    @Override
    public E peek() {
        return peekFirst();
    }

    
    @Override
    public int remainingCapacity() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return capacity - count;
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public int drainTo(Collection c) {
        return drainTo(c, Integer.MAX_VALUE);
    }

    
    @Override
    public int drainTo(Collection c, int maxElements) {
        if (c == null) {
            throw new NullPointerException();
        }
        if (c == this) {
            throw new IllegalArgumentException();
        }
        if (maxElements <= 0) {
            return 0;
        }
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int n = Math.min(maxElements, count);
            for (int i = 0; i < n; i++) {
                c.add(first.item);   // In this order, in case add() throws.
                unlinkFirst();
            }
            return n;
        } finally {
            lock.unlock();
        }
    }

    // Stack methods

    
    @Override
    public void push(E e) {
        addFirst(e);
    }

    
    @Override
    public E pop() {
        return removeFirst();
    }

    // Collection methods

    
    @Override
    public boolean remove(Object o) {
        return removeFirstOccurrence(o);
    }

    
    @Override
    public int size() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return count;
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public boolean contains(Object o) {
        if (o == null) {
            return false;
        }
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            for (Node p = first; p != null; p = p.next) {
                if (o.equals(p.item)) {
                    return true;
                }
            }
            return false;
        } finally {
            lock.unlock();
        }
    }

    

//     
//     public boolean addAll(Collection c) {
//         if (c == null)
//             throw new NullPointerException();
//         if (c == this)
//             throw new IllegalArgumentException();
//         final ReentrantLock lock = this.lock;
//         lock.lock();
//         try {
//             boolean modified = false;
//             for (E e : c)
//                 if (linkLast(e))
//                     modified = true;
//             return modified;
//         } finally {
//             lock.unlock();
//         }
//     }

    
    @Override
    @SuppressWarnings("unchecked")
    public Object[] toArray() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            Object[] a = new Object[count];
            int k = 0;
            for (Node p = first; p != null; p = p.next) {
                a[k++] = p.item;
            }
            return a;
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    @SuppressWarnings("unchecked")
    public  T[] toArray(T[] a) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            if (a.length < count) {
                a = (T[]) java.lang.reflect.Array.newInstance
                        (a.getClass().getComponentType(), count);
            }
            int k = 0;
            for (Node p = first; p != null; p = p.next) {
                a[k++] = (T) p.item;
            }
            if (a.length > k) {
                a[k] = null;
            }
            return a;
        } finally {
            lock.unlock();
        }
    }

    @Override
    public String toString() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            Node p = first;
            if (p == null) {
                return "[]";
            }
            StringBuilder sb = new StringBuilder();
            sb.append('[');
            for (; ; ) {
                E e = p.item;
                sb.append(e == this ? "(this Collection)" : e);
                p = p.next;
                if (p == null) {
                    return sb.append(']').toString();
                }
                sb.append(',').append(' ');
            }
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public void clear() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            for (Node f = first; f != null; ) {
                f.item = null;
                Node n = f.next;
                f.prev = null;
                f.next = null;
                f = n;
            }
            first = last = null;
            count = 0;
            notFull.signalAll();
        } finally {
            lock.unlock();
        }
    }

    
    @Override
    public Iterator iterator() {
        return new Itr();
    }

    
    @Override
    public Iterator descendingIterator() {
        return new DescendingItr();
    }

    
    private abstract class AbstractItr implements Iterator {
        
        Node next;

        
        E nextItem;

        
        private Node lastRet;

        abstract Node firstNode();

        abstract Node nextNode(Node n);

        AbstractItr() {
            // set to initial position
            final ReentrantLock lock = ResizableCapacitylinkedBlockingQueue.this.lock;
            lock.lock();
            try {
                next = firstNode();
                nextItem = (next == null) ? null : next.item;
            } finally {
                lock.unlock();
            }
        }

        
        private Node succ(Node n) {
            // Chains of deleted nodes ending in null or self-links
            // are possible if multiple interior nodes are removed.
            for (; ; ) {
                Node s = nextNode(n);
                if (s == null) {
                    return null;
                } else if (s.item != null) {
                    return s;
                } else if (s == n) {
                    return firstNode();
                } else {
                    n = s;
                }
            }
        }

        
        void advance() {
            final ReentrantLock lock = ResizableCapacitylinkedBlockingQueue.this.lock;
            lock.lock();
            try {
                // assert next != null;
                next = succ(next);
                nextItem = (next == null) ? null : next.item;
            } finally {
                lock.unlock();
            }
        }

        @Override
        public boolean hasNext() {
            return next != null;
        }

        @Override
        public E next() {
            if (next == null) {
                throw new NoSuchElementException();
            }
            lastRet = next;
            E x = nextItem;
            advance();
            return x;
        }

        @Override
        public void remove() {
            Node n = lastRet;
            if (n == null) {
                throw new IllegalStateException();
            }
            lastRet = null;
            final ReentrantLock lock = ResizableCapacitylinkedBlockingQueue.this.lock;
            lock.lock();
            try {
                if (n.item != null) {
                    unlink(n);
                }
            } finally {
                lock.unlock();
            }
        }
    }

    
    private class Itr extends AbstractItr {
        @Override
        Node firstNode() {
            return first;
        }

        @Override
        Node nextNode(Node n) {
            return n.next;
        }
    }

    
    private class DescendingItr extends AbstractItr {
        @Override
        Node firstNode() {
            return last;
        }

        @Override
        Node nextNode(Node n) {
            return n.prev;
        }
    }

    
    static final class LBDSpliterator implements Spliterator {
        static final int MAX_BATCH = 1 << 25;  // max batch array size;
        final ResizableCapacitylinkedBlockingQueue queue;
        Node current;    // current node; null until initialized
        int batch;          // batch size for splits
        boolean exhausted;  // true when no more nodes
        long est;           // size estimate

        LBDSpliterator(ResizableCapacitylinkedBlockingQueue queue) {
            this.queue = queue;
            this.est = queue.size();
        }

        @Override
        public long estimateSize() {
            return est;
        }

        @Override
        public Spliterator trySplit() {
            Node h;
            final ResizableCapacitylinkedBlockingQueue q = this.queue;
            int b = batch;
            int n = (b <= 0) ? 1 : (b >= MAX_BATCH) ? MAX_BATCH : b + 1;
            if (!exhausted &&
                    ((h = current) != null || (h = q.first) != null) &&
                    h.next != null) {
                Object[] a = new Object[n];
                final ReentrantLock lock = q.lock;
                int i = 0;
                Node p = current;
                lock.lock();
                try {
                    if (p != null || (p = q.first) != null) {
                        do {
                            if ((a[i] = p.item) != null) {
                                ++i;
                            }
                        } while ((p = p.next) != null && i < n);
                    }
                } finally {
                    lock.unlock();
                }
                if ((current = p) == null) {
                    est = 0L;
                    exhausted = true;
                } else if ((est -= i) < 0L) {
                    est = 0L;
                }
                if (i > 0) {
                    batch = i;
                    return Spliterators.spliterator
                            (a, 0, i, Spliterator.ORDERED | Spliterator.NonNULL |
                                    Spliterator.CONCURRENT);
                }
            }
            return null;
        }

        @Override
        public void forEachRemaining(Consumer action) {
            if (action == null) {
                throw new NullPointerException();
            }
            final ResizableCapacitylinkedBlockingQueue q = this.queue;
            final ReentrantLock lock = q.lock;
            if (!exhausted) {
                exhausted = true;
                Node p = current;
                do {
                    E e = null;
                    lock.lock();
                    try {
                        if (p == null) {
                            p = q.first;
                        }
                        while (p != null) {
                            e = p.item;
                            p = p.next;
                            if (e != null) {
                                break;
                            }
                        }
                    } finally {
                        lock.unlock();
                    }
                    if (e != null) {
                        action.accept(e);
                    }
                } while (p != null);
            }
        }

        @Override
        public boolean tryAdvance(Consumer action) {
            if (action == null) {
                throw new NullPointerException();
            }
            final ResizableCapacitylinkedBlockingQueue q = this.queue;
            final ReentrantLock lock = q.lock;
            if (!exhausted) {
                E e = null;
                lock.lock();
                try {
                    if (current == null) {
                        current = q.first;
                    }
                    while (current != null) {
                        e = current.item;
                        current = current.next;
                        if (e != null) {
                            break;
                        }
                    }
                } finally {
                    lock.unlock();
                }
                if (current == null) {
                    exhausted = true;
                }
                if (e != null) {
                    action.accept(e);
                    return true;
                }
            }
            return false;
        }

        @Override
        public int characteristics() {
            return Spliterator.ORDERED | Spliterator.NonNULL |
                    Spliterator.CONCURRENT;
        }
    }

    
    @Override
    public Spliterator spliterator() {
        return new LBDSpliterator(this);
    }

    
    private void writeObject(java.io.ObjectOutputStream s)
            throws java.io.IOException {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            // Write out capacity and any hidden stuff
            s.defaultWriteObject();
            // Write out all elements in the proper order.
            for (Node p = first; p != null; p = p.next) {
                s.writeObject(p.item);
            }
            // Use trailing null as sentinel
            s.writeObject(null);
        } finally {
            lock.unlock();
        }
    }

    
    private void readObject(java.io.ObjectInputStream s)
            throws java.io.IOException, ClassNotFoundException {
        s.defaultReadObject();
        count = 0;
        first = null;
        last = null;
        // Read in all elements and place in queue
        for (; ; ) {
            @SuppressWarnings("unchecked")
            E item = (E) s.readObject();
            if (item == null) {
                break;
            }
            add(item);
        }
    }
}

自定义线程池，增加每个线程处理的耗时，以及平均耗时、最大耗时、最小耗时，以及输出监控日志信息等等；

public class ThreadPoolMonitor extends ThreadPoolExecutor {

    private static final Logger LOGGER = LoggerFactory.getLogger(ThreadPoolMonitor.class);

    
    private static final RejectedExecutionHandler defaultHandler = new AbortPolicy();

    
    private String poolName;

    
    private Long minCostTime;

    
    private Long maxCostTime;
    
    private AtomicLong totalCostTime = new AtomicLong();

    private ThreadLocal startTimeThreadLocal = new ThreadLocal<>();

    
    public ThreadPoolMonitor(int corePoolSize, int maximumPoolSize, long keepAliveTime,
                             TimeUnit unit, BlockingQueue workQueue, String poolName) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
                Executors.defaultThreadFactory(), poolName);
    }


    
    public ThreadPoolMonitor(int corePoolSize, int maximumPoolSize, long keepAliveTime,
                             TimeUnit unit, BlockingQueue workQueue, RejectedExecutionHandler handler, String poolName) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
                Executors.defaultThreadFactory(), handler, poolName);
    }


    
    public ThreadPoolMonitor(int corePoolSize, int maximumPoolSize, long keepAliveTime,
                             TimeUnit unit, BlockingQueue workQueue,
                             ThreadFactory threadFactory, String poolName) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, defaultHandler);
        this.poolName = poolName;
    }


    
    public ThreadPoolMonitor(int corePoolSize, int maximumPoolSize, long keepAliveTime,
                             TimeUnit unit, BlockingQueue workQueue,
                             ThreadFactory threadFactory, RejectedExecutionHandler handler, String poolName) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
        this.poolName = poolName;
    }


    
    @Override
    public void shutdown() {
        // 统计已执行任务、正在执行任务、未执行任务数量
        LOGGER.info("{} 关闭线程池， 已执行任务: {}, 正在执行任务: {}, 未执行任务数量: {}",
                this.poolName, this.getCompletedTaskCount(), this.getActiveCount(), this.getQueue().size());
        super.shutdown();
    }

    
    @Override
    public List shutdownNow() {
        // 统计已执行任务、正在执行任务、未执行任务数量
        LOGGER.info("{} 立即关闭线程池，已执行任务: {}, 正在执行任务: {}, 未执行任务数量: {}",
                this.poolName, this.getCompletedTaskCount(), this.getActiveCount(), this.getQueue().size());
        return super.shutdownNow();
    }

    
    @Override
    protected void beforeExecute(Thread t, Runnable r) {
        startTimeThreadLocal.set(System.currentTimeMillis());
    }

    
    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        long costTime = System.currentTimeMillis() - startTimeThreadLocal.get();
        startTimeThreadLocal.remove();
        maxCostTime = maxCostTime > costTime ? maxCostTime : costTime;
        if (getCompletedTaskCount() == 0) {
            minCostTime = costTime;
        }
        minCostTime = minCostTime < costTime ? minCostTime : costTime;
        totalCostTime.addAndGet(costTime);
        LOGGER.info("{}-pool-monitor: " +
                        "任务耗时: {} ms, 初始线程数: {}, 核心线程数: {}, 执行的任务数量: {}, " +
                        "已完成任务数量: {}, 任务总数: {}, 队列里缓存的任务数量: {}, 池中存在的最大线程数: {}, " +
                        "最大允许的线程数: {},  线程空闲时间: {}, 线程池是否关闭: {}, 线程池是否终止: {}",
                this.poolName,
                costTime, this.getPoolSize(), this.getCorePoolSize(), this.getActiveCount(),
                this.getCompletedTaskCount(), this.getTaskCount(), this.getQueue().size(), this.getLargestPoolSize(),
                this.getMaximumPoolSize(), this.getKeepAliveTime(TimeUnit.MILLISECONDS), this.isShutdown(), this.isTerminated());
    }


    public Long getMinCostTime() {
        return minCostTime;
    }

    public Long getMaxCostTime() {
        return maxCostTime;
    }

    public long getAverageCostTime(){
        if(getCompletedTaskCount()==0||totalCostTime.get()==0){
            return 0;
        }
        return totalCostTime.get()/getCompletedTaskCount();
    }

    
    static class MonitorThreadFactory implements ThreadFactory {
        private static final AtomicInteger poolNumber = new AtomicInteger(1);
        private final ThreadGroup group;
        private final AtomicInteger threadNumber = new AtomicInteger(1);
        private final String namePrefix;

        
        MonitorThreadFactory(String poolName) {
            SecurityManager s = System.getSecurityManager();
            group = Objects.nonNull(s) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
            namePrefix = poolName + "-pool-" + poolNumber.getAndIncrement() + "-thread-";
        }

        @Override
        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0);
            if (t.isDaemon()) {
                t.setDaemon(false);
            }
            if (t.getPriority() != Thread.NORM_PRIORITY) {
                t.setPriority(Thread.NORM_PRIORITY);
            }
            return t;
        }
    }
}

动态修改线程池的类，通过Spring的监听器监控配置刷新方法，实现动态更新线程池的参数；

@Component
@Slf4j
public class DynamicThreadPoolManager {


    @Autowired
    private DynamicThreadPoolProperties dynamicThreadPoolProperties;

    
    public Map threadPoolExecutorMap = new HashMap<>();


    public Map getThreadPoolExecutorMap() {
        return threadPoolExecutorMap;
    }


    
    @PostConstruct
    public void init() {
        createThreadPools(dynamicThreadPoolProperties);
    }

    
    private void createThreadPools(DynamicThreadPoolProperties dynamicThreadPoolProperties) {
        dynamicThreadPoolProperties.getExecutors().forEach(config -> {
            if (!threadPoolExecutorMap.containsKey(config.getThreadPoolName())) {
                ThreadPoolMonitor threadPoolMonitor = new ThreadPoolMonitor(
                        config.getCorePoolSize(),
                        config.getMaxPoolSize(),
                        config.getKeepAliveTime(),
                        config.getUnit(),
                        new ResizableCapacitylinkedBlockingQueue<>(config.getQueueCapacity()),
                        RejectedExecutionHandlerEnum.getRejectedExecutionHandler(config.getRejectedExecutionType()),
                        config.getThreadPoolName()
                );
                threadPoolExecutorMap.put(config.getThreadPoolName(),
                        threadPoolMonitor);
            }

        });
    }

    
    private void changeThreadPools(DynamicThreadPoolProperties dynamicThreadPoolProperties) {
        dynamicThreadPoolProperties.getExecutors().forEach(config -> {
            ThreadPoolExecutor threadPoolExecutor = threadPoolExecutorMap.get(config.getThreadPoolName());
            if (Objects.nonNull(threadPoolExecutor)) {
                threadPoolExecutor.setCorePoolSize(config.getCorePoolSize());
                threadPoolExecutor.setMaximumPoolSize(config.getMaxPoolSize());
                threadPoolExecutor.setKeepAliveTime(config.getKeepAliveTime(), config.getUnit());
                threadPoolExecutor.setRejectedExecutionHandler(RejectedExecutionHandlerEnum.getRejectedExecutionHandler(config.getRejectedExecutionType()));
                BlockingQueue queue = threadPoolExecutor.getQueue();
                if (queue instanceof ResizableCapacitylinkedBlockingQueue) {
                    ((ResizableCapacitylinkedBlockingQueue) queue).setCapacity(config.getQueueCapacity());
                }
            }
        });
    }


    @EventListener
    public void envListener(EnvironmentChangeEvent event) {
        log.info("配置发生变更" + event);
        changeThreadPools(dynamicThreadPoolProperties);
    }

}

DynamicThreadPoolPropertiesController对外暴露两个方法，第一个通过ContextRefresher提供对外刷新配置的接口，实现及时更新配置信息，第二提供一个查询接口的方法，

@RestController
public class DynamicThreadPoolPropertiesController {

    @Autowired
    private ContextRefresher contextRefresher;


    @Autowired
    private DynamicThreadPoolProperties dynamicThreadPoolProperties;


    @Autowired
    private DynamicThreadPoolManager dynamicThreadPoolManager;


    @PostMapping("/threadPool/properties")
    public void update() {
        ThreadPoolProperties threadPoolProperties =
                dynamicThreadPoolProperties.getExecutors().get(0);
        threadPoolProperties.setCorePoolSize(20);
        threadPoolProperties.setMaxPoolSize(50);
        threadPoolProperties.setQueueCapacity(200);
        threadPoolProperties.setRejectedExecutionType("CallerRunsPolicy");
        contextRefresher.refresh();
    }

    @GetMapping("/threadPool/properties")
    public Map queryThreadPoolProperties() {
        Map metricMap = new HashMap<>();
        List threadPools = new ArrayList<>();
        dynamicThreadPoolManager.getThreadPoolExecutorMap().forEach((k, v) -> {
            ThreadPoolMonitor threadPoolMonitor = (ThreadPoolMonitor) v;
            Map poolInfo = new HashMap<>();
            poolInfo.put("thread.pool.name", k);
            poolInfo.put("thread.pool.core.size", threadPoolMonitor.getCorePoolSize());
            poolInfo.put("thread.pool.largest.size", threadPoolMonitor.getLargestPoolSize());
            poolInfo.put("thread.pool.max.size", threadPoolMonitor.getMaximumPoolSize());
            poolInfo.put("thread.pool.thread.count", threadPoolMonitor.getPoolSize());
            poolInfo.put("thread.pool.max.costTime", threadPoolMonitor.getMaxCostTime());
            poolInfo.put("thread.pool.average.costTime", threadPoolMonitor.getAverageCostTime());
            poolInfo.put("thread.pool.min.costTime", threadPoolMonitor.getMinCostTime());
            poolInfo.put("thread.pool.active.count", threadPoolMonitor.getActiveCount());
            poolInfo.put("thread.pool.completed.taskCount", threadPoolMonitor.getCompletedTaskCount());
            poolInfo.put("thread.pool.queue.name", threadPoolMonitor.getQueue().getClass().getName());
            poolInfo.put("thread.pool.rejected.name", threadPoolMonitor.getRejectedExecutionHandler().getClass().getName());
            poolInfo.put("thread.pool.task.count", threadPoolMonitor.getTaskCount());
            threadPools.add(poolInfo);
        });
        metricMap.put("threadPools", threadPools);
        return metricMap;
    }

}

整体上的流程到这里就完成了，算是一个Demo版，对于该组件更深入的思考我认为还可以做以下三件事情:

应该以starter的形式嵌入到应用，通过判断启动类加载的Appllo、Nacos还是默认实现；对外可以Push、也可以是日志，还可以支持各种库，提供丰富的输出形式，这个样子的话更加通用化；提供统一查询接口、修改接口、增加权限校验、增加预警规则配置；

参考以下内容:

美团文章

结束

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基于Spring Boot的线程池监控方案

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