sentinel之自定义线程池工厂的使用

前言：

线程池是我们在开发工作中经常使用到的。JDK提供了Executors来快速创建线程池。

本文从那些开源框架中来分析下，他们是怎么更好的创建线程池

1.Executors分析

    我们常规使用Executors创建线程池如下：

// 创建一个固定线程池
ExecutorService threadPool = Executors.newFixedThreadPool(5);

1.1 源码角度释义Executors

public class Executors {
    public static ExecutorService newFixedThreadPool(int nThreads) {
        // 设置核心参数
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue());
    }
}


public class ThreadPoolExecutor extends AbstractExecutorService {
	public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue workQueue) {
        // 我们主要来讨论下threadFactory的创建
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             Executors.defaultThreadFactory(), defaultHandler);
    }
    
    // 最终线程池的参数就是如下这些入参
    public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue workQueue,
                              ThreadFactory threadFactory,
                              RejectedExecutionHandler handler) {
        if (corePoolSize < 0 ||
            maximumPoolSize  poolType, boolean daemon) {
        this(poolType, daemon, Thread.NORM_PRIORITY);
    }

    public DefaultThreadFactory(String poolName, boolean daemon) {
        this(poolName, daemon, Thread.NORM_PRIORITY);
    }

    public DefaultThreadFactory(Class poolType, int priority) {
        this(poolType, false, priority);
    }

    public DefaultThreadFactory(String poolName, int priority) {
        this(poolName, false, priority);
    }

    public DefaultThreadFactory(Class poolType, boolean daemon, int priority) {
        this(toPoolName(poolType), daemon, priority);
    }

    public static String toPoolName(Class poolType) {
        ObjectUtil.checkNotNull(poolType, "poolType");

        String poolName = StringUtil.simpleClassName(poolType);
        switch (poolName.length()) {
            case 0:
                return "unknown";
            case 1:
                return poolName.toLowerCase(Locale.US);
            default:
                if (Character.isUpperCase(poolName.charAt(0)) && Character.isLowerCase(poolName.charAt(1))) {
                    return Character.toLowerCase(poolName.charAt(0)) + poolName.substring(1);
                } else {
                    return poolName;
                }
        }
    }

    // 可以看到，这里不但提供了线程名称前缀和daemon，而且支持用户设置线程级别和threadGroup
    public DefaultThreadFactory(String poolName, boolean daemon, int priority, ThreadGroup threadGroup) {
        ObjectUtil.checkNotNull(poolName, "poolName");

        if (priority < Thread.MIN_PRIORITY || priority > Thread.MAX_PRIORITY) {
            throw new IllegalArgumentException(
                    "priority: " + priority + " (expected: Thread.MIN_PRIORITY