我正在尝试处理一个包含超过 20K 行的大 Excel 文件。每行都应保存为数据存储中的实体。首先，我使用 Blobstore 在 servlet 中获取 excel 文件，然后使用任务队列服务对任务进行排队。此任务读取 Excel 文件，将每一行转换为实体并将其存储。正如我之前所说，Excel 文件可能有超过 20K 行。一段时间后，我得到了这个异常:
com.xxx.xxx.ProcessBlob doPost: |POST|ProcessBlob|Exception:Task was cancelled.|Msg:Task was cancelled.|Stack:java.util.concurrent.CancellationException: Task was cancelled.
at com.google.common.util.concurrent.AbstractFuture.cancellationExceptionWithCause(AbstractFuture.java:796)
at com.google.common.util.concurrent.AbstractFuture.getDoneValue(AbstractFuture.java:475)
at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:381)
at com.google.common.util.concurrent.AbstractFuture$TrustedFuture.get(AbstractFuture.java:85)
at com.google.appengine.tools.development.TimedFuture.get(TimedFuture.java:42)
at com.google.common.util.concurrent.ForwardingFuture.get(ForwardingFuture.java:63)
at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:88)
at com.google.appengine.api.datastore.Batcher$ReorderingMultiFuture.get(Batcher.java:131)
at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:88)
at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:88)
at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:88)
at com.google.appengine.api.datastore.FutureHelper.getInternal(FutureHelper.java:75)
at com.google.appengine.api.datastore.FutureHelper.quietGet(FutureHelper.java:35)
at com.google.appengine.api.datastore.DatastoreServiceImpl.put(DatastoreServiceImpl.java:56)
at com.xxx.xxx.xxx.createEntity(EntityService.java:87)
at com.xxx.xxx.ProcessBlob.doPost(ProcessBlob.java:145)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.JdbcMySqlConnectionCleanupFilter.doFilter(JdbcMySqlConnectionCleanupFilter.java:60)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:254)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$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:146)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:527)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444)
at com.google.tracing.CurrentContext.runInContext(CurrentContext.java:220)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:724)
Caused by: java.util.concurrent.CancellationException: Future.cancel() was called.
at com.google.common.util.concurrent.AbstractFuture.cancel(AbstractFuture.java:514)
at com.google.appengine.tools.development.TimedFuture.cancel(TimedFuture.java:85)
at com.google.common.util.concurrent.ForwardingFuture.cancel(ForwardingFuture.java:48)
at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.cancel(ApiProxyImpl.java:553)
at com.google.apphosting.runtime.RequestManager.cancelPendingAsyncFutures(RequestManager.java:626)
at com.google.apphosting.runtime.RequestManager.sendDeadline(RequestManager.java:399)
at com.google.apphosting.runtime.RequestManager.sendDeadline(RequestManager.java:357)
at com.google.apphosting.runtime.CloneControllerImpl.sendDeadline(CloneControllerImpl.java:201)
at com.google.apphosting.sandbox.ModelClonePb$CloneController$ServiceParameters$3.handleRequest(ModelClonePb.java:1166)
at com.google.net.rpc3.impl.server.RpcServerInternalContext.runRpcInApplication(RpcServerInternalContext.java:558)
at com.google.net.rpc3.impl.server.RpcServerChannel$1.run(RpcServerChannel.java:871)
at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56)
at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:626)
at com.google.net.rpc3.impl.server.RpcServerChannel.startRpc(RpcServerChannel.java:837)
at com.google.net.rpc3.impl.server.RpcServerChannel.receivedMessage(RpcServerChannel.java:594)
at com.google.net.rpc3.impl.server.RpcServerChannel.access$2700(RpcServerChannel.java:164)
at com.google.net.rpc3.impl.server.RpcServerChannel$TransportCallback.receivedMessage(RpcServerChannel.java:2365)
at com.google.net.rpc3.impl.wire.RpcBaseTransport.receivedMessage(RpcBaseTransport.java:457)
at com.google.apphosting.runtime.udrpc.UdrpcTransport$ServerAdapter.receivedMessage(UdrpcTransport.java:707)
at com.google.apphosting.runtime.udrpc.UdrpcTransport.dispatchPacket(UdrpcTransport.java:384)
at com.google.apphosting.runtime.udrpc.UdrpcTransport.readPackets(UdrpcTransport.java:283)
at com.google.apphosting.runtime.udrpc.UdrpcTransport$1.run(UdrpcTransport.java:100)
at com.google.net.eventmanager.AbstractFutureTask$Sync.innerRun(AbstractFutureTask.java:260)
at com.google.net.eventmanager.AbstractFutureTask.run(AbstractFutureTask.java:121)
at com.google.net.eventmanager.EventManagerImpl.runTask(EventManagerImpl.java:594)
at com.google.net.eventmanager.EventManagerImpl.internalRunWorkerLoop(EventManagerImpl.java:1011)
at com.google.net.eventmanager.EventManagerImpl.runWorkerLoop(EventManagerImpl.java:892)
at com.google.net.eventmanager.WorkerThreadInfo.runWorkerLoop(WorkerThreadInfo.java:161)
at com.google.net.eventmanager.EventManagerImpl$WorkerThread.run(EventManagerImpl.java:1879)
另一个“奇怪”的事情是，查看请求的日志，当它丢弃该异常时，参数“ms”和“cpu_ms”几乎相同。也许我超出了 AppEngine 限制或超时限制？
[02/Mar/2015:21:11:32 -0800] "POST /tasks/ProcessBlob HTTP/1.1" 200 0 "http://xxx.appspot.com/upload" "AppEngine-Google; (+http://code.google.com/appengine)" "xxx.appspot.com" ms=599492 cpu_ms=32522 queue_name=default task_name=xxx instance=xxx app_engine_release=1.9.18
[02/Mar/2015:23:21:55 -0800] "POST /tasks/ProcessBlob HTTP/1.1" 200 0 "http://xxx.appspot.com/upload" "AppEngine-Google; (+http://code.google.com/appengine)" "xxx.appspot.com" ms=599420 cpu_ms=33262 queue_name=default task_name=xxx instance=xxx app_engine_release=1.9.18
最佳答案
您似乎遇到了任务队列限制，599949 毫秒 == 10 分钟。根据文档:
Tasks targeted at an automatic scaled module must finish execution within 10 minutes. If you have tasks that require more time or computing resources, they can be sent to manual or basic scaling modules, where they can run up to 24 hours.
参见文档:https://cloud.google.com/appengine/docs/java/taskqueue/overview-push#task_deadlines
我建议将任务分成几个较小的任务，比如每 1000 条记录一个任务，也许更小
关于保存数据存储实体时出现 java.util.concurrent.CancellationException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28853418/