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为ThreadPoolExecutor处理异常

threadpoolexecutor exception-handling concurrency multithreading java

jagamot · 技术社区 · 15 年前

我有以下代码片段,它基本上扫描了需要执行的任务列表,然后将每个任务交给执行者执行。

这个 JobExecutor 然后创建另一个执行器(用于执行db任务…将数据读写到队列)并完成任务。

作业执行器 返回A Future<Boolean> 对于提交的任务。当其中一个任务失败时,我希望通过捕获所有异常来优雅地中断所有线程并关闭执行器。我需要做什么改变?

public class DataMovingClass {
    private static final AtomicInteger uniqueId = new AtomicInteger(0);

  private static final ThreadLocal<Integer> uniqueNumber = new IDGenerator();   

  ThreadPoolExecutor threadPoolExecutor  = null ;

   private List<Source> sources = new ArrayList<Source>();

    private static class IDGenerator extends ThreadLocal<Integer> {
        @Override
        public Integer get() {
            return uniqueId.incrementAndGet();
        }
  }

  public void init(){

    // load sources list

  }

  public boolean execute() {

    boolean succcess = true ; 
    threadPoolExecutor = new ThreadPoolExecutor(10,10,
                10, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(1024),
                new ThreadFactory() {
                    public Thread newThread(Runnable r) {
                        Thread t = new Thread(r);
                        t.setName("DataMigration-" + uniqueNumber.get());
                        return t;
                    }// End method
                }, new ThreadPoolExecutor.CallerRunsPolicy());

     List<Future<Boolean>> result = new ArrayList<Future<Boolean>>();

     for (Source source : sources) {
                    result.add(threadPoolExecutor.submit(new JobExecutor(source)));
     }

     for (Future<Boolean> jobDone : result) {
                try {
                    if (!jobDone.get(100000, TimeUnit.SECONDS) && success) {
                        // in case of successful DbWriterClass, we don't need to change
                        // it.
                        success = false;
                    }
                } catch (Exception ex) {
                    // handle exceptions
                }
            }

  }

  public class JobExecutor implements Callable<Boolean>  {

        private ThreadPoolExecutor threadPoolExecutor ;
        Source jobSource ;
        public SourceJobExecutor(Source source) {
            this.jobSource = source;
            threadPoolExecutor = new ThreadPoolExecutor(10,10,10, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(1024),
                    new ThreadFactory() {
                        public Thread newThread(Runnable r) {
                            Thread t = new Thread(r);
                            t.setName("Job Executor-" + uniqueNumber.get());
                            return t;
                        }// End method
                    }, new ThreadPoolExecutor.CallerRunsPolicy());
        }

        public Boolean call() throws Exception {
            boolean status = true ; 
            System.out.println("Starting Job = " + jobSource.getName());
            try {

                        // do the specified task ; 


            }catch (InterruptedException intrEx) {
                logger.warn("InterruptedException", intrEx);
                status = false ;
            } catch(Exception e) {
                logger.fatal("Exception occurred while executing task "+jobSource.getName(),e);
                status = false ;
            }
           System.out.println("Ending Job = " + jobSource.getName());
            return status ;
        }
    }
}

3 回复 | 直到 8 年前

Ravindra babu 9 年前

当你向执行者提交任务时,它会返回一个 FutureTask 实例。

FutureTask.get() 将作为 ExecutorException .

所以当你在 List<Future> 打电话给每个人,接住 执行者例外 启动有序关闭。

Community CDub 8 年前

因为您要将任务提交给 ThreadPoolExecutor ,异常被 FutureTask .

看看这个 code

**Inside FutureTask$Sync**

void innerRun() {
    if (!compareAndSetState(READY, RUNNING))
        return;

  runner = Thread.currentThread();
    if (getState() == RUNNING) { // recheck after setting thread
        V result;
       try {
            result = callable.call();
        } catch (Throwable ex) {
           setException(ex);
            return;
        }
       set(result);
    } else {
        releaseShared(0); // cancel
    }

}

protected void setException(Throwable t) {
   sync.innerSetException(t);
}

从上面的代码来看,很明显 setException 方法捕获 Throwable . 因为这个原因, 未来任务 如果你使用 submit() 方法 线程池

按Java documentation ,您可以扩展 afterExecute() 方法在 线程池

protected void afterExecute(Runnable r,
                            Throwable t)

文档中的示例代码:

class ExtendedExecutor extends ThreadPoolExecutor {
   // ...
   protected void afterExecute(Runnable r, Throwable t) {
     super.afterExecute(r, t);
     if (t == null && r instanceof Future<?>) {
       try {
         Object result = ((Future<?>) r).get();
       } catch (CancellationException ce) {
           t = ce;
       } catch (ExecutionException ee) {
           t = ee.getCause();
       } catch (InterruptedException ie) {
           Thread.currentThread().interrupt(); // ignore/reset
       }
     }
     if (t != null)
       System.out.println(t);
   }
 }

你可以抓住 Exceptions 在三个方面

Future.get() 如公认答案所示
包整 run() 或 call() 方法在 try{}catch{}Exceptoion{} 阻碍
重写 afterExecute 属于 线程池 方法如上所示

要优雅地中断其他线程,请查看以下SE问题:

How to stop next thread from running in a ScheduledThreadPoolExecutor

How to forcefully shutdown java ExecutorService

Ravindra babu 8 年前

子类 ThreadPoolExecutor 并覆盖它 protected afterExecute (Runnable r, Throwable t) 方法。

如果要通过 java.util.concurrent.Executors 便利类(你不是),看看它的源代码,看看它是如何调用的 ThreadPoolExecutor .