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我的應用程序一直只用了一個月的時間，只有偶爾的截止日期超出例外。今天早上，在五分鐘的時間裏，我超過了150個截止日期。現在恢復正常了。我知道這可能會發生，並且不一定會通過我在代碼中執行的任何操作來解決，但每個異常在堆棧跟蹤中都有appstats（至少20我仔細看過）。一方面，這暗示了appstats - 另一方面，我認爲appstats可能在每個運行的單個堆棧跟蹤中。我試圖確定是否appstats是問題。這個異常是否意味着appstats鎖定了我的appengine應用程序？
我不是一個過濾器的專家 - 任何人都可以告訴我，如果像下面這樣的堆棧跟蹤意味着代碼長時間在appstats中等待嗎？它似乎確實意味着這一點，但我認爲過濾器可能會混淆堆棧跟蹤。此外，即使它在appstats中等待 - 看起來問題可能是數據庫不可用（在全局appengine狀態頁面上沒有明顯問題）。
我在明顯的appstats呼叫的開頭放了星號，用於快速掃描。
javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract com.activegrade.shared.dto.ResultDTO com.activegrade.client.serviceinterfaces.CourseOperationService.getCourseList(com.activegrade.shared.dto.AuthInfo)' threw an unexpected exception: com.google.apphosting.api.DeadlineExceededException: This request (1ff876185c635baf) started at 2010/11/30 14:35:47.278 UTC and was still executing at 2010/11/30 14:36:16.261 UTC.
at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:378)
at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:581)
at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:207)
at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:243)
at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:713)
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$CachedChain.doFilter(ServletHandler.java:1166)
**at com.google.appengine.tools.appstats.AppstatsFilter.doFilter(AppstatsFilter.java:140)**
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
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$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)
Caused by: com.google.apphosting.api.DeadlineExceededException: This request (1ff876185c635baf) started at 2010/11/30 14:35:47.278 UTC and was still executing at 2010/11/30 14:36:16.261 UTC.
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:502)
**at com.google.appengine.tools.appstats.RecordingFuture.get(RecordingFuture.java:99)
**at com.google.appengine.tools.appstats.RecordingFuture$ExtendedFuture.get(RecordingFuture.java:44)
at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:42)
at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:42)
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.QueryResultsSourceImpl.loadMoreEntities(QueryResultsSourceImpl.java:69)
at com.google.appengine.api.datastore.QueryResultsSourceImpl.loadMoreEntities(QueryResultsSourceImpl.java:56)
at com.google.appengine.api.datastore.QueryResultIteratorImpl.ensureLoaded(QueryResultIteratorImpl.java:156)
at com.google.appengine.api.datastore.QueryResultIteratorImpl.hasNext(QueryResultIteratorImpl.java:65)
at org.datanucleus.store.appengine.DatastoreElementContainerStoreSpecialization.getChildren(DatastoreElementContainerStoreSpecialization.java:105)
at org.datanucleus.store.appengine.DatastoreFKListStore.listIterator(DatastoreFKListStore.java:48)
at org.datanucleus.store.mapped.scostore.AbstractListStore.listIterator(AbstractListStore.java:84)
at org.datanucleus.store.mapped.scostore.AbstractListStore.iterator(AbstractListStore.java:74)
at org.datanucleus.sco.backed.List.loadFromStore(List.java:241)
at org.datanucleus.sco.backed.List.initialise(List.java:190)
at org.datanucleus.sco.SCOUtils.newSCOInstance(SCOUtils.java:183)
at org.datanucleus.store.mapped.mapping.AbstractContainerMapping.replaceFieldWithWrapper(AbstractContainerMapping.java:426)
at org.datanucleus.store.mapped.mapping.AbstractContainerMapping.postFetch(AbstractContainerMapping.java:444)
at org.datanucleus.store.appengine.DatastorePersistenceHandler.runPostFetchMappingCallbacks(DatastorePersistenceHandler.java:510)
at org.datanucleus.store.appengine.DatastorePersistenceHandler.fetchObject(DatastorePersistenceHandler.java:489)
at org.datanucleus.store.appengine.query.DatastoreQuery.entityToPojo(DatastoreQuery.java:565)
at org.datanucleus.store.appengine.DatastoreRelationFieldManager.lookupOneToOneChild(DatastoreRelationFieldManager.java:320)
at org.datanucleus.store.appengine.DatastoreRelationFieldManager.fetchRelationField(DatastoreRelationFieldManager.java:274)
at org.datanucleus.store.appengine.DatastoreFieldManager.fetchObjectField(DatastoreFieldManager.java:289)
at org.datanucleus.state.AbstractStateManager.replacingObjectField(AbstractStateManager.java:1197)
at com.activegrade.server.dao.Course.jdoReplaceField(Course.java)
at com.activegrade.server.dao.Course.jdoReplaceFields(Course.java)
at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2772)
at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2791)
at org.datanucleus.store.appengine.DatastorePersistenceHandler.fetchObject(DatastorePersistenceHandler.java:480)
at org.datanucleus.store.appengine.query.DatastoreQuery.entityToPojo(DatastoreQuery.java:565)
at org.datanucleus.store.appengine.query.DatastoreQuery.entityToPojo(DatastoreQuery.java:520)
at org.datanucleus.store.appengine.query.DatastoreQuery.access$300(DatastoreQuery.java:110)
at org.datanucleus.store.appengine.query.DatastoreQuery$6.apply(DatastoreQuery.java:638)
at org.datanucleus.store.appengine.query.DatastoreQuery$6.apply(DatastoreQuery.java:630)
at org.datanucleus.store.appengine.query.LazyResult.resolveNext(LazyResul