线程假死排查

背景

测试环境发现有部分业务执行一次后就不再执行了，出现了线程假死情况

排查过程

1. 查看日志

通过日志看到在备份文件时有异常发生，但是代码时将该异常捕获了，正常情况是不会导致线程假死的情况，需要进一步排查

2. 查看业务代码，先判断是否有明显bug

经排查后没发现明显bug

3. 将业务代码抽象出伪代码，本地debug查看原因

伪代码
代码实现的业务功能为：将指定文件使用多线程挪到备份目录


@RunWith(JUnit4.class)
@Slf4j
public class BatchExecuteTest {
    private final static ExecutorService FILE_PROCESS_WORKER = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());

    @Test
    public void threadStopTest() {
        try {
            ArrayList<String> fileNames = Lists.newArrayList("test1.txt", "test2.txt", "test3.txt");
            while (true) {
                String dsType = "sftp";
                String ip = "192.168.130.21";
                String port = "22";
                String username = "test";
                String password = "test";
                String connectPattern = "PORT";
                FileHelper ftpHelper = FileManager.getFtpHelper("", dsType, ip, port, username, password, connectPattern);
                batchExecute(fileNames, fileName -> {
                    try {
                        String sourcePath = Paths.get("/data1/upload/test", fileName).toString();
                        String targetPath = Paths.get("/data1/upload/test/bak", fileName).toString();
                        ftpHelper.move(sourcePath, targetPath);
                    } catch (Exception e) {
                        log.error("移动文件到失败", e);
                    }
                });
                ftpHelper.close();
            }
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }
    }

    private <T> void batchExecute(List<T> processList, Consumer<T> consumer) throws InterruptedException {
        if (CollectionUtils.isEmpty(processList)) {
            return;
        }
        if (processList.size() == 1) {
            consumer.accept(processList.get(0));
            return;
        }
        CountDownLatch countDownLatch = new CountDownLatch(processList.size());
        for (T t : processList) {
            FILE_PROCESS_WORKER.execute(() -> {
                try {
                    consumer.accept(t);
                } finally {
                    countDownLatch.countDown();
                }
            });
        }
        countDownLatch.await();
    }

}