处理 HardDeadlineExceededError 的任务策略

Question

我有许多任务/servlet 遇到了 HardDeadlineExceededError，这使得所有内容都处于“仍在执行”状态。

正在完成的工作很容易超过 29 秒的阈值。

我尝试捕获 DeadlineExceededException 和基本异常以保存退出 状态但这些异常处理程序都没有被捕获...

有没有办法确定哪些任务在队列中或当前正在执行？

还有其他策略可以应对这种情况吗？

我正在处理的情况记录在“请求计时器”下标题。

// task handler for retrieving information from external web services
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {

    String taskRetryCountParam = req.getParameter( "X-AppEngine-TaskRetryCount" );
    int taskRetryCount = (taskRetryCountParam==null) ? 0 : Integer.parseInt(taskRetryCountParam);
            // look up the persistent 'task' and mark it as 'running'

    logger.info( this.getClass().getName() + ".doPost( "+ taskId + " ) retryCount=" + taskRestryCount );


    // Do lots of heavy lifting here 
    // like calling external web services using URL fetch service
            // and saving the contents into our database.

            // look up the persistent 'task' and mark it as 'completed'

    } catch ( DeadlineExceededException deadline ) {
        // got this deadline exception
                    // look up the persistent 'task' and mark it as 'errored - try again'
        logger.warning( "DeadlineExceeded Exception while loading content " + deadline.getMessage() );
        resp.setStatus( HttpServletResponse.SC_REQUEST_TIMEOUT );

        }
    } catch ( Exception unknown ) {
        // got some unknown exception
                    // look up the persistent 'task' and mark it as 'errored - cancelled'
        logger.severe( "General Exception while loading content  exception:" + unknown.getMessage() );
        resp.setStatus( HttpServletResponse.SC_OK );

    }
}

---

这是我遇到这种情况时的日志文件条目...看来我的数据库事务在进行时花费了太长时间。

  W 05-30 12:42PM 09.535
  Error for /loadstatus
  com.google.apphosting.runtime.HardDeadlineExceededError: This request (083793d1091c2ca3) started at 2010/05/30 19:41:39.814 UTC and was still executing at 2010/05/30 19:42:09.529 UTC.
    at java.lang.Object.wait(Native Method)
    at java.lang.Object.wait(Object.java:443)
    at java.util.concurrent.TimeUnit.timedWait(Unknown Source)
    at com.google.apphosting.runtime.AsyncFuture.get(AsyncFuture.java:60)
    at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.get(ApiProxyImpl.java:326)
    at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.get(ApiProxyImpl.java:217)
    at com.google.apphosting.runtime.ApiProxyImpl.doSyncCall(ApiProxyImpl.java:131)
    at com.google.apphosting.runtime.ApiProxyImpl.access$000(ApiProxyImpl.java:43)
    at com.google.apphosting.runtime.ApiProxyImpl$1.run(ApiProxyImpl.java:104)
    at com.google.apphosting.runtime.ApiProxyImpl$1.run(ApiProxyImpl.java:102)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.google.apphosting.runtime.ApiProxyImpl.makeSyncCall(ApiProxyImpl.java:102)
    at com.google.apphosting.runtime.ApiProxyImpl.makeSyncCall(ApiProxyImpl.java:43)
    at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:98)
    at com.google.appengine.api.datastore.DatastoreApiHelper.makeSyncCall(DatastoreApiHelper.java:58)
    at com.google.appengine.api.datastore.TransactionImpl.makeSyncCall(TransactionImpl.java:42)
    at com.google.appengine.api.datastore.TransactionImpl.makeSyncCall(TransactionImpl.java:56)
    at com.google.appengine.api.datastore.TransactionImpl.commit(TransactionImpl.java:66)
    at org.datanucleus.store.appengine.DatastoreTransaction.commit(DatastoreTransaction.java:61)
    at org.datanucleus.store.appengine.DatastoreXAResource.commit(DatastoreXAResource.java:88)
    at org.datanucleus.transaction.Transaction.commit(Transaction.java:149)
    at org.datanucleus.transaction.TransactionManager.commit(TransactionManager.java:95)
    at org.datanucleus.TransactionImpl.internalCommit(TransactionImpl.java:390)
    at org.datanucleus.TransactionImpl.commit(TransactionImpl.java:258)
    at org.datanucleus.jdo.JDOTransaction.commit(JDOTransaction.java:83)
    at org.datanucleus.store.appengine.jdo.DatastoreJDOTransaction.commit(DatastoreJDOTransaction.java:56)
    <snip>
  C 05-30 12:42PM 09.629
  Uncaught exception from servlet
  com.google.apphosting.runtime.HardDeadlineExceededError: This request (083793d1091c2ca3) started at 2010/05/30 19:41:39.814 UTC and was still executing at 2010/05/30 19:42:09.529 UTC.
    at java.lang.Object.wait(Native Method)
    at java.lang.Object.wait(Object.java:443)
    at java.util.concurrent.TimeUnit.timedWait(Unknown Source)
    at com.google.apphosting.runtime.AsyncFuture.get(AsyncFuture.java:60)
    at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.get(ApiProxyImpl.java:326)
    at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.get(ApiProxyImpl.java:217)
    at com.google.apphosting.runtime.ApiProxyImpl.doSyncCall(ApiProxyImpl.java:131)
    at com.google.apphosting.runtime.ApiProxyImpl.access$000(ApiProxyImpl.java:43)
    at com.google.apphosting.runtime.ApiProxyImpl$1.run(ApiProxyImpl.java:104)
    at com.google.apphosting.runtime.ApiProxyImpl$1.run(ApiProxyImpl.java:102)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.google.apphosting.runtime.ApiProxyImpl.makeSyncCall(ApiProxyImpl.java:102)
    at com.google.apphosting.runtime.ApiProxyImpl.makeSyncCall(ApiProxyImpl.java:43)
    at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:98)
    at com.google.appengine.api.datastore.DatastoreApiHelper.makeSyncCall(DatastoreApiHelper.java:58)
    at com.google.appengine.api.datastore.TransactionImpl.makeSyncCall(TransactionImpl.java:42)
    at com.google.appengine.api.datastore.TransactionImpl.makeSyncCall(TransactionImpl.java:56)
    at com.google.appengine.api.datastore.TransactionImpl.commit(TransactionImpl.java:66)
    at org.datanucleus.store.appengine.DatastoreTransaction.commit(DatastoreTransaction.java:61)
    at org.datanucleus.store.appengine.DatastoreXAResource.commit(DatastoreXAResource.java:88)
    at org.datanucleus.transaction.Transaction.commit(Transaction.java:149)
    at org.datanucleus.transaction.TransactionManager.commit(TransactionManager.java:95)
    at org.datanucleus.TransactionImpl.internalCommit(TransactionImpl.java:390)
    at org.datanucleus.TransactionImpl.commit(TransactionImpl.java:258)
    at org.datanucleus.jdo.JDOTransaction.commit(JDOTransaction.java:83)
    at org.datanucleus.store.appengine.jdo.DatastoreJDOTransaction.commit(DatastoreJDOTransaction.java:56)
    <snip>
  W 05-30 12:42PM 09.644
  A serious problem was encountered with the process that handled this request, causing it to exit. This is likely to cause a new process to be used for the next request to your application. If you see this message frequently, you may be throwing exceptions during the initialization of your application. (Error code 104)

Answer 1

http://groups.google.com/group/google-appengine- java/msg/e3fd2b621bb96013

如果发生在您自己的代码中，则可以在没有 DEE 的情况下抛出 HDEE。
通常最耗时的事情是等待 API 调用
返回，因此此处超时将导致 API 调用停止并显示
迪伊。所以如果你不经常调用API，你可以直接点击HDEE。

我还有长时间运行的任务来迭代数据处理
并存储结果。我使用停止返回结果的迭代器
20 秒后并保存最后处理的对象，然后踢
关闭新任务以继续处理。

我原来的解决方案捕获了 DEE，然后进行了清理，但是这个
停止可靠工作。