java - 为什么从 App Engine 数据存储中获取 MakePersistentAll 中的 DeadlineExceededException？

Question

伙计们——我收到以下异常，无法解释原因。要保留的对象数量通常很少(<10)，但是当我从 persistencemanager 使用 makepersistentall 时，我会间歇性地收到 DeadlineExceededException。

在调用 makepersistentall 之前，http 请求代码还会处理对数据存储的其他查询。查看异常跟踪，似乎有一些与等待对象相关的东西。

问题是什么，我该如何解决这个异常？谢谢

====

相关代码是

  // handle the updates
  List<InterestQueueItem> interested = getInterestedUsers(locx, locy, gamecode);  // this also results in a query into the datastore, which looks like it goes well
  List <BingoUpdate> topersisteUpdates = new ArrayList<BingoUpdate>();
     try {
   for (InterestQueueItem item: interested) {
    if (!item.getUID().equals(this.uid)) {   // no need to update the originator of the update
     BingoUpdate update = new BingoUpdate(item, screenname+" not working");
     update.setContent("some content");
     topersisteUpdates.add(update);
    }
   }
   pm.makePersistentAll(topersisteUpdates); // exception thrown here
     } finally {
      pm.close();
     }     

BingoUpdate 构造函数并没有做太多事情 -- 只是 getter 和 setter。

GetInterestedUsers 是

public static List<InterestQueueItem> getInterestedUsers(float locx, float locy, String gamecode) {
List<InterestQueueItem> retVal = new ArrayList<InterestQueueItem>();
    PersistenceManager pm = PMF.get().getPersistenceManager();
Query query = pm.newQuery(InterestQueueItem.class);
    try {
        // reduce the potential set of interested folks
        query.setFilter("gamecode == thisGameCode");
        query.declareParameters("String thisGameCode");                 
        retVal.addAll((List <InterestQueueItem>) query.execute(gamecode));
        return retVal;
    } finally {
        pm.close();
    }
}

异常如下:

Uncaught exception from servlet
com.google.apphosting.api.DeadlineExceededException: This request (61c89aa7e7f35f42) started at 2010/10/26 03:56:13.421 UTC and was still executing at 2010/10/26 03:56:42.750 UTC.
 at java.lang.Object.wait(Native Method)
 at java.lang.Object.wait(Object.java:502)
 at com.google.apphosting.runtime.AsyncFuture.get(AsyncFuture.java:54)
 at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.get(ApiProxyImpl.java:412)
 at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.get(ApiProxyImpl.java:244)
 at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:42)
 at com.google.appengine.api.datastore.FutureHelper$CumulativeAggregateFuture.get(FutureHelper.java:136)
 at com.google.appengine.api.datastore.FutureHelper.getInternal(FutureHelper.java:71)
 at com.google.appengine.api.datastore.FutureHelper.quietGet(FutureHelper.java:32)
 at com.google.appengine.api.datastore.DatastoreServiceImpl$2.runInternal(DatastoreServiceImpl.java:115)
 at com.google.appengine.api.datastore.DatastoreServiceImpl$2.runInternal(DatastoreServiceImpl.java:112)
 at com.google.appengine.api.datastore.TransactionRunner.runInTransaction(TransactionRunner.java:31)
 at com.google.appengine.api.datastore.DatastoreServiceImpl.put(DatastoreServiceImpl.java:112)
 at org.datanucleus.store.appengine.RuntimeExceptionWrappingDatastoreService.put(RuntimeExceptionWrappingDatastoreService.java:117)
 at org.datanucleus.store.appengine.DatastorePersistenceHandler.put(DatastorePersistenceHandler.java:182)
 at org.datanucleus.store.appengine.DatastorePersistenceHandler.put(DatastorePersistenceHandler.java:127)
 at org.datanucleus.store.appengine.DatastorePersistenceHandler.insertObjects(DatastorePersistenceHandler.java:254)
 at org.datanucleus.store.appengine.BatchPutManager.processBatchState(BatchPutManager.java:35)
 at org.datanucleus.store.appengine.BatchManager.finish(BatchManager.java:54)
 at org.datanucleus.store.appengine.jdo.DatastoreJDOPersistenceManager$BatchManagerWrapper.call(DatastoreJDOPersistenceManager.java:127)
 at org.datanucleus.store.appengine.jdo.DatastoreJDOPersistenceManager$BatchManagerWrapper.access$200(DatastoreJDOPersistenceManager.java:121)
 at org.datanucleus.store.appengine.jdo.DatastoreJDOPersistenceManager.makePersistentAll(DatastoreJDOPersistenceManager.java:98)
 at com.goodconcierge.UpdateQueueThread.run(UpdateQueueThread.java:112)
 at com.goodconcierge.BingoServerServlet.handleLeave(BingoServerServlet.java:92)
 at com.goodconcierge.BingoServerServlet.doGet(BingoServerServlet.java:24)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:693)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
 at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
 at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
 at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97)
 at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
 at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
 at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
 at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
 at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
 at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
 at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
 at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:238)
 at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
 at org.mortbay.jetty.Server.handle(Server.java:326)
 at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
 at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
 at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
 at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
 at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
 at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:261)
 at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:8486)
 at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:8484)
 at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24)
 at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:418)
 at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:572)
 at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
 at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
 at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
 at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
 at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
 at java.lang.Thread.run(Thread.java:636)

Answer 1

你整个 HTTP 请求超过 30 秒就被杀死了。

尽管异常指向“全部保留”调用，但它可能不是根本原因。例如，getInterestedUsers 可能需要 29 秒，而 persist() 根本没有时间完成。您应该在代码行周围放置跟踪以测量它们花费的时间。

如果发现根本原因确实是 persist()，请确保您没有上述必要的级联持久性。您可能只有几个顶级对象，但如果它们具有一对多链接，您可能会加载并持久化数千个对象，而您并没有意识到这一点。

尝试在本地机器上运行代码，监控实际的 SQL 语句(我不记得 AppEngine 是否允许？它应该)。