private static int maxThreads(ContainerThreadpoolConfig config, int cpus) {
        if (config.maxThreads() > 0) return config.maxThreads();
        else if (config.maxThreads() == 0) return 4 * cpus;
        else return Math.max(MIN_THREADS_WHEN_SCALE_FACTOR, Math.abs(config.maxThreads()) * cpus);
    }
Shutdown the thread pool, give a grace period of 1 second before forcibly
shutting down all worker threads.
container-core/src/main/java/com/yahoo/container/handler/threadpool/ContainerThreadpoolImpl.java