sleep（）与阻塞函数 是不是会一直占用cpu ？

Posted 2023-05-12

在应用程序中，sleep（） 或者 一些读写，同步的阻塞函数，当资源请求没有满足时会阻塞等待，那么在这等待是的时间中会占用cpu 时间吗，sleep （） 函数呢

当然不会，不然一个程序sleep 10s，系统岂不是要阻塞10s 参考技术A sleep是让出cpu。它占的时间仅仅是cpu切换的时间 参考技术B 应该不会占用cpu，在sleep期间，cpu会调度其他进程

解决YED画图CPU占用100%的问题

背景

公司很多项目都会用到YED包来画关联方的关联图，当某个公司的4度关联方个数过多以及关联关系太过复杂时，使用YED画图会造成CPU占用一直100%并且长时间占用不释放CPU资源。所以在使用YED画图的代码流程设计需要一些技巧来保证YED画图不会阻塞主线程，并且确保当图片长时间无法绘制成功时，需要有一种机制强制终止绘制，避免CPU资源长时间无意义的浪费。

解决方案思考

1. 找出YED无法完成绘制的原因。从根本上解决。
2. 如果无法从根本上解决至少需要解决长时间CPU100%占用。

尝试解决

首先尝试了找寻问题的根本原因，提出3个假设：由于数据有问题？YED代码bug？数据量过大造成内存不足？ 然而遗憾的是时间有限从这3方面入手都并没有进展，如果各位同事有兴趣可以尝试找出根本原因，有进展可与我联系。

所以开始尝试超时终止绘制方案，具体思路如下：

1. 在需要YED画图时，使用别的线程进行绘制避免主线程阻塞
2. 使用线程池管理线程，避免高并发时线程无限制增加
3. 通过其他线程等待一定时间，如果绘制还是没有完成中断绘制尝试

阅读YED源代码发现，项目中使用的YED版本并不响应线程中断，所以只有使用stop()方法强制终止线程，这样我们就需要在线程池中取到需要终止的线程，考虑自定义一个连接池，连接池中维护一个以任务为key，以执行这个任务线程为value的map，让我们在需要时可以使用任务取到对应的线程并终止它。

同时应产品要求如果4度图片绘制失败需要尝试3度图片绘制，3度失败再尝试2度，所以提交任务时需要传入一个供用户回调的接口。

用以上思路代码实现大致如下：

自定义线程池如下：

public class TraceThreadPoolExecutor extends ThreadPoolExecutor {

    // 1 minutes
    private static final int            MONITOR_SHUTDOWN_TIMEOUT = 60;

    private final Map<Runnable, Thread> tracer                   = new ConcurrentHashMap<>();

    private final ExecutorService       monitor;

    /**
     * Submit a job and monitor elapse time, if job elapse time greater than
     * timeout threshold, force stop it.
     * 
     * @param job
     * @param timeOut
     * @param timeUnit
     * @param handler   When job timeout, call it.
     * @return
     */
    public Future<?> submitJob(Runnable job, int timeOut, TimeUnit timeUnit, TimeOutHandler handler) {
        Future<?> future = submit(job);
        monitor.submit(new MonitorJob(job, future, timeOut, timeUnit, handler));
        return future;
    }

    /**
     * Stop executor & monitor, if timeout, force stop.
     */
    public void stop() {
        /** Stop monitor executor */
        shutdownExecutorQuietly(monitor);

        /** Stop worker executor */
        shutdownExecutorQuietly(this);
    }

    private void shutdownExecutorQuietly(ExecutorService executor) {
        if (null != executor) {
            try {
                executor.shutdown();
                if (!executor.isShutdown()) {
                    try {
                        executor.awaitTermination(MONITOR_SHUTDOWN_TIMEOUT, TimeUnit.SECONDS);
                    } catch (InterruptedException ignore) {
                    }

                    /** 等待超时或被中断，直接强制停止 */
                    if (!executor.isShutdown()) {
                        executor.shutdownNow();
                    }
                }
            } catch (Exception ignore) {
                // do nothing
            }
        }
    }

    @Override
    protected void beforeExecute(Thread worker, Runnable job) {
        traceThread(job, worker);
    }

    @Override
    protected void afterExecute(Runnable job, Throwable error) {
        removeTraceThread(job);
    }

    @SuppressWarnings("rawtypes")
    private class MonitorJob implements Runnable {

        private final Future<?>      future;

        private final Runnable       originJob;

        private final int            timeOut;

        private final TimeUnit       timeUnit;

        private final TimeOutHandler handler;

        public MonitorJob(Runnable originJob, Future<?> future, int timeOut, TimeUnit timeUnit, TimeOutHandler handler) {
            this.originJob = originJob;
            this.future = future;
            this.timeOut = timeOut;
            this.timeUnit = timeUnit;
            this.handler = handler;
        }

        @Override
        public void run() {
            if (null != future) {
                try {
                    future.get(timeOut, timeUnit);
                } catch (InterruptedException ignore) {
                } catch (ExecutionException ignore) {
                } catch (TimeoutException timeOut) {
                    /** Stop worker thread force */
                    Thread worker = getTraceThread((FutureTask) future);
                    if (null != worker && worker.isAlive()) {
                        worker.stop();
                    }

                    /** Do callback */
                    if (null != handler) {
                        handler.doHandle(originJob);
                    }
                }
            }
        }
    }

    private void traceThread(Runnable job, Thread worker) {
        tracer.put(job, worker);
    }

    private Thread getTraceThread(Runnable job) {
        return tracer.get(job);
    }

    private void removeTraceThread(Runnable job) {
        tracer.remove(job);
    }

    private TraceThreadPoolExecutor(int workerThreads, int monitorThreads) {
        super(workerThreads, workerThreads, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>());
        monitor = Executors.newFixedThreadPool(monitorThreads);
    }

    public static TraceThreadPoolExecutor createFixedThreadPool(int workerThreads, int monitorThreads) {
        return new TraceThreadPoolExecutor(workerThreads, monitorThreads);
    }
}

并发任务处理代码如下：

@Component
@Lazy(false)
public class TasksHandler {

    @Value("${system.processor.num:2}")
    private int                     processors;

    @Value("${system.monitor.num:2}")
    private int                     monitorProcessors;

    /**
     * 日志
     */
    private final Logger            logger = LoggerFactory.getLogger(TasksHandler.class);

    private TraceThreadPoolExecutor executor;

    @Autowired
    private JobScheduleService      jobScheduleService;

    @Autowired
    private FileFactory             fileFactory;

    @PostConstruct
    public void initialize() {
        executor = TraceThreadPoolExecutor.createFixedThreadPool(processors, monitorProcessors);
        List<JobSchedule> jobSchedules = jobScheduleService.selectByStatuses(Lists.newArrayList(NEW, CREATING));
        jobSchedules.forEach(jobSchedule -> submitJob(jobSchedule));

    }

    @PreDestroy
    public void stop() {
        executor.stop();
    }

    public void submitJob(JobSchedule jobSchedule) {
        Map<Object, Object> params = new HashMap<>();
        switch (jobSchedule.getJobType()) {
            case "DNA":
                params.put("dnaDeep", 4);
                break;
            case "HTML":
                break;
            case "PDF":
                params.put("bothTemplate", true);
                break;
        }
        executor.submitJob(new TaskThread(fileFactory, jobScheduleService, jobSchedule, params), 5, TimeUnit.MINUTES, job -> {
            switch (jobSchedule.getJobType()) {
                case "DNA":
                    recursionHandler(jobSchedule, params);
                    break;
                case "HTML":
                    logger.info("HTML第一次生成超时，稍后进行重试");
                    retryHandler(jobSchedule, params);
                    break;
                case "PDF":
                    logger.info("PDF第一次生成超时，稍后进行重试");
                    retryHandler(jobSchedule, params);
                    break;
            }
        });
    }

    private void recursionHandler(JobSchedule jobSchedule, Map params) {
        if ((int) params.get("dnaDeep") == 1)
            return;
        logger.info("{}度DNA生成超时，开始尝试生成{}度DNA", params.get("dnaDeep"), (int) params.get("dnaDeep") - 1);
        params.put("dnaDeep", (int) params.get("dnaDeep") - 1);
        executor.submitJob(new TaskThread(fileFactory, jobScheduleService, jobSchedule, params), 2, TimeUnit.MINUTES, dnaJob -> {
            recursionHandler(jobSchedule, params);
        });
    }

    private void retryHandler(JobSchedule jobSchedule, Map params) {
        executor.submitJob(new TaskThread(fileFactory, jobScheduleService, jobSchedule, params), 5, TimeUnit.MINUTES, job -> {
            switch (jobSchedule.getJobType()) {
                case "HTML":
                    logger.info("HTML生成超时 id:{}, companyName:{}", jobSchedule.getId(), jobSchedule.getCompanyName());
                    break;
                case "PDF":
                    logger.info("PDF生成超时 id:{}, companyName:{}", jobSchedule.getId(), jobSchedule.getCompanyName());
                    break;
            }
        });
    }

}