private void closeInternal() {
        boolean terminated;

        threadpool.shutdown();
        try {
            terminated = threadpool.awaitTermination(1, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            return;
        }
        if (!terminated) {
            threadpool.shutdownNow();
        }
    }
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