Nacos fails to start when the cpu core is less than 2

[wyp12]

Nacos fails to start when the cpu core is less than 2，Exception appear when start：

java.lang.ExceptionInInitializerError: null
        at com.alibaba.nacos.naming.healthcheck.AbstractHealthCheckProcessor.<clinit>(AbstractHealthCheckProcessor.java:148)
        at com.alibaba.nacos.naming.healthcheck.HealthCheckTask.run(HealthCheckTask.java:61)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:756)
Caused by: java.lang.IllegalArgumentException: null
        at java.util.concurrent.ThreadPoolExecutor.<init>(ThreadPoolExecutor.java:1307)
        at java.util.concurrent.ThreadPoolExecutor.<init>(ThreadPoolExecutor.java:1230)
        at java.util.concurrent.Executors.newFixedThreadPool(Executors.java:151)
        at com.alibaba.nacos.naming.healthcheck.MysqlHealthCheckProcessor.<clinit>(MysqlHealthCheckProcessor.java:52)
        ... 9 common frames omitted

Reason：

    private static final ScheduledExecutorService EXECUTOR = Executors
            .newScheduledThreadPool(Runtime.getRuntime().availableProcessors() / 2, new ThreadFactory() {
                @Override
                public Thread newThread(Runnable r) {
                    Thread thread = new Thread(r);
                    thread.setDaemon(true);
                    thread.setName("com.alibaba.nacos.naming.health");
                    return thread;
                }
            });

Runtime.getRuntime().availableProcessors() / 2 value is 0, when invoker ThreadPoolExecutor(),
throw new IllegalArgumentException();

  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.corePoolSize = corePoolSize;
        this.maximumPoolSize = maximumPoolSize;
        this.workQueue = workQueue;
        this.keepAliveTime = unit.toNanos(keepAliveTime);
        this.threadFactory = threadFactory;
        this.handler = handler;
    }