线程池监控2-监控线程池状态、线程数量和队列任务数量等

1.实现原理

　　这篇博文是基于线程池监控1-监控任务执行时间，原理是：创建一个固定时间间隔执行的线程，来记录线程池的池状态、线程数量和队列任务数量等，具体方案：使用单例类缓存所有创建的线程池对象，类创建时启动定时任务线程，定期遍历缓存中线程池，记录线程池信息。
2.实现代码
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package com.xkzhangsan.thread.pool.monitor;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**

• 全局监控
  
• 1.定期记录线程池基本信息
  
  *

• @author xkzhangsan
  */
  public class GlobalMonitor {
  private static volatile GlobalMonitor instance;
  private static final ConcurrentHashMap threadPoolMonitorMap = new ConcurrentHashMap<>();
  private static final ScheduledThreadPoolExecutor scheduledThreadPoolExecutor = new ScheduledThreadPoolExecutor(1);

  private GlobalMonitor() {

   scheduledThreadPoolExecutor.scheduleAtFixedRate(new PoolInfoRunnable(), 10, 10, TimeUnit.SECONDS);
  

  }

  public static GlobalMonitor getInstance() {

   if (instance == null) {
       synchronized (GlobalMonitor.class) {
           if (instance == null) {
               instance = new GlobalMonitor();
           }
       }
   }
   return instance;
  

  }

  public void put(String poolName, ThreadPoolMonitor threadPoolMonitor) {

   threadPoolMonitorMap.put(poolName, threadPoolMonitor);
  

  }

  public void remove(String poolName) {

   threadPoolMonitorMap.remove(poolName);
  

  }

  static class PoolInfoRunnable implements Runnable {

   @Override
   public void run() {
       threadPoolMonitorMap.forEach((poolName, threadPoolMonitor) -> {
           int currentPoolSize = threadPoolMonitor.getPoolSize();
           int queueSize = threadPoolMonitor.getQueue().size();
           System.out.println("poolName:" + poolName + " status:" + threadPoolMonitor.getStatus() + " corePoolSize:" + threadPoolMonitor.getCorePoolSize() + " maximumPoolSize:"
                   + threadPoolMonitor.getMaximumPoolSize() + " currentPoolSize:" + currentPoolSize + " queueCapacity:" + threadPoolMonitor.getQueueCapacity()
                   + " queueSize:" + queueSize);
       });
   }
  

  }

}

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获取线程池状态

这里参考了ThreadPoolExecutor的toString()，返回Running、Shutting down、Terminated 三种状态。

见:ThreadPoolMonitor类
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public String getStatus() {
    if (super.isTerminated()) {
        return "Terminated";
    } else if (super.isShutdown()) {
        return "Shutting down";
    } else {
        return "Running";
    }
}

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获取队列总容量

创建ThreadPoolExecutor时，传入的BlockingQueue workQueue，无法直接获取总容量，ThreadPoolExecutor又没有直接获取总容量的方法，
这里想到另一个方法，Queue的remainingCapacity()返回当前队列剩余容量，原理：总容量-队列size，所以，在刚创建时size为0，返回的就时总容量。
见:ThreadPoolMonitor类
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private void init(String poolName, MonitorLevelEnum monitorLevel) {
    this.poolName = poolName;
    this.monitorLevel = monitorLevel;
    this.taskStartTimeMap = new ConcurrentHashMap<>();
    if (isPoolMonitor()) {
        GlobalMonitor.getInstance().put(poolName, this);
    }
    this.queueCapacity = super.getQueue().remainingCapacity();
}

public int getQueueCapacity() {
    return this.queueCapacity;
}

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3.测试运行
3.1 测试代码
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package com.xkzhangsan.thread.pool.monitor;

import com.xkzhangsan.thread.pool.monitor.constant.MonitorLevelEnum;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.TimeUnit;

public class ThreadPoolMonitorTest {

public static void main(String[] args) throws InterruptedException {
    poolMonitor();
}

public static void poolMonitor() throws InterruptedException {
    ThreadPoolMonitor threadPoolMonitor = new ThreadPoolMonitor(1, 3, 0, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<>(1000), "test", MonitorLevelEnum.POOL);
    for (int i = 0; i < 100; i++) {
        int finalI = i;
        threadPoolMonitor.execute(() -> {
            try {
                TimeUnit.SECONDS.sleep(3);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
            System.out.println(finalI);
        });
    }
    //因为调用shutdown方法会将threadPoolMonitor从监控缓存中删除，这里sleep 100s
    TimeUnit.SECONDS.sleep(100);
    //线程池必须手动关闭，否则一直运行
    threadPoolMonitor.shutdown();
}

}

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3.2 测试结果
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0
1
2
poolName:test status:Shutting down corePoolSize:1 maximumPoolSize:3 currentPoolSize:1 queueCapacity:1000 queueSize:96
3
4
5
poolName:test status:Shutting down corePoolSize:1 maximumPoolSize:3 currentPoolSize:1 queueCapacity:1000 queueSize:93
6
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poolName:test status:Shutting down corePoolSize:1 maximumPoolSize:3 currentPoolSize:1 queueCapacity:1000 queueSize:90
9

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线程sleep 3s，监控日志10s打印一次，队列中的任务在不断被消费减少。

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