Question

I host my application on google app engine. What my application should do is every two minutes connects to a website, parses it and send the necessary info to my device using C2DM. I first tested my application to see if it works once. And it works fine. But inorder to check the webiste every two minutes I put the necessary methods in a while loop and then put Thread.sleep(120000) in the while loop. It wokred for a while but now I get this:
Uncaught exception from servlet
com.google.apphosting.runtime.HardDeadlineExceededError: This request (f6b9f0b8e1ec6f23) started at 2011/06/09 10:24:22.514 UTC and was still executing at 2011/06/09 10:24:52.824 UTC.

So before the two minute thing every thing was ok.

and this is the whole error message:

Uncaught exception from servlet
com.google.apphosting.runtime.HardDeadlineExceededError: This request (f6b9f0b8e1ec6f23) started at 2011/06/09 10:24:22.514 UTC and was still executing at 2011/06/09 10:24:52.824 UTC.

at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:408)
at java.lang.StringBuilder.append(StringBuilder.java:136)
at java.lang.StringBuilder.<init>(StringBuilder.java:110)
at tripplannerServer.ParseVerstoring.parsePlanned(ParseVerstoring.java:50)
at tripplannerServer.SendMessage2.geplandeVerstoring(SendMessage2.java:257)
at tripplannerServer.TripplannerServerServlet.doGet(TripplannerServerServlet.java:152)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
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$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$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$RequestHandler.headerComplete(HttpConnection.java:923)
at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:260)
at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9669)
at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:439)
at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
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)

Any idea how to solve this? Or the idea to use Thread.sleep() is not good? If not how can I make the application check the website every two minutes?

Thank you in advance.

Answer 1

Any front-end app should be finished in 30 sec(HardDeadline). You have basically 2 options,

1. (better one)change your app logic, avoid Thread.sleep() and use cron.xml instead to start your app every x minutes. In your case, always-on or taskQueue simply won’t help.
2. change to Backends so you can run your app continuously.