java线程等待死进程完成

Question

我编写了一个java类来执行多线程任务,每个任务都运行一个外部进程.该过程负责将".chp"文件转换为".txt"文件.它用C语写.

这个过程在某个时刻中断,因为当我在终端中查看"顶部"时它会消失(可能是由于chp文件损坏).问题是我的java线程中的进程没有返回."process.waitFor()"似乎永远持续下去(至少是我为ExecutorService指定的12小时).

我做错了什么(没有捕捉异常？)？我尝试在MyThread中设置一个String类型的类变量,并输入一个错误消息代替抛出一个新的RuntimeException,然后在main的末尾打印String,但是线程代码没有达到这一点.它仍然停留在waitFor().

一旦C程序失败,进程是否应该终止？

程序在终端上打印(cf:MyThread):

A
B
C

主要:

String pathToBin = "/path/to/bin";
List<MyThread> threadList = new ArrayList<MyThread>();

for (File f : folderList) {
    File[] chpFilesInFolder = f.listFiles(new FilenameFilter() {

        @Override
        public boolean accept(File dir, String name) {
            if (name.endsWith(".chp")){
                 return true;
            }else{
                 return false;
            }
        }
    });
    File chpFile = writeChpFiles(chpFilesInFolder);
    String[] cmd = {pathToBin, "--arg1", chpFile, "--out-dir", outputFolder};
    MyThread t = new MyThread(cmd, f, chpFilesInFolder);
    threadList.add(t);
}

ExecutorService threadExecutor = Executors.newFixedThreadPool(4);
for(MyThread th : threadList){
    threadExecutor.execute(th);
}
threadExecutor.shutdown();

try {
    threadExecutor.awaitTermination(12, TimeUnit.HOURS);
} catch (InterruptedException e) {
    e.printStackTrace();
}

MyThread的:

class MyThread extends Thread{
    private String[] cmd;
    private File chpFolder;
    private File[] chpFilesInFolder;

    public MyThread(String[] cmd, File chpFolder, File[] chpFilesInFolder){
        this.cmd = cmd;
        this.chpFolder = chpFolder;
        this.chpFilesInFolder = chpFilesInFolder;
    }

    @Override
    public void run() {
        Process process = null;
        try{
            System.err.println("A ");
            ProcessBuilder procBuilder = new ProcessBuilder(cmd);
            procBuilder.redirectErrorStream(true);

            System.err.println("B");
            process = procBuilder.start();

            System.err.println("C");
            process.waitFor();

            System.err.println("D");
            if(process.exitValue()!=0) System.err.println("ERROR !"+process.exitValue());

            System.err.println("E");
        }catch(IOException e){
            e.printStackTrace();
        }catch(InterruptedException e){
            e.printStackTrace();
        }catch(Throwable e){
            e.printStackTrace();
        }finally{
            System.err.println("F");
            if(process!=null) {try { process.destroy();} catch(Exception err) {err.printStackTrace();}}
        }

        File[] txtFilesInFolder = chpFolder.listFiles(new FilenameFilter() {

            @Override
            public boolean accept(File dir, String name) {
                if (name.endsWith(".chp.txt")){
                    return true;
                }else{
                    return false;
                }
            }
        });

        if (txtFilesInFolder.length==chpFilesInFolder.length){
            for (File chp : chpFilesInFolder) {
                chp.delete();
            }
            File logFile = new File(chpFolder, "apt-chp-to-txt.log");
               if (logFile.exists()){
                   logFile.delete();
               }
        }else{
            throw new RuntimeException("CHPs have not all been transformed to TXT in "+chpFolder.getAbsolutePath());
        }

Answer 1

您的 C 程序是否有可能在 stdout 上生成输出？如果是这样，您需要在 Process.waitFor() 返回之前读取 Process.getOutputStream() - 请参阅https://bugs.java.com/bugdatabase/view_bug?bug_id=4254231

或者，将您的 C 程序称为重定向 stdout 的 shell 脚本。

您可以使用 jstack 命令来确认线程确实被阻塞在 Process.waitFor() 处。