this is my first google app engine servlet which i wanted to make it crawling a website so i created threads using backgroundThread in app engine, my problem is when i run this application on the localhost:8888 it works correctly and do the task it's supposed to do.
Youm7 youm7Crawler = new Youm7();
log.info("start 1");
Thread youm7Thread = ThreadManager.createBackgroundThread(youm7Crawler);
log.info("start 2");
log.info("start 3");
youm7Thread.start();
but once i try deploying it as on server i got an error 500 server and i get this critical error in the log
`Uncaught exception from servlet
java.lang.IllegalStateException: This feature is only available to backend instances.
at com.google.appengine.api.system.SystemServiceImpl.translateException(SystemServiceImpl.java:40)
at com.google.appengine.api.system.SystemServiceImpl.startBackgroundRequest(SystemServiceImpl.java:28)
at com.google.apphosting.runtime.ApiProxyImpl$BackgroundThreadFactory.newThread(ApiProxyImpl.java:1125)
at com.google.appengine.api.ThreadManager.createBackgroundThread(ThreadManager.java:88)
at newscrawler.crawlerServlet.doGet(crawlerServlet.java:30)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java: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:57)
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:266)
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:438)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:480)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:487)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:774)
at com.google.tracing.TraceContext$DoInTraceContext.runInContext(TraceContext.java:751)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:342)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:334)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:484)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:722)
2013-04-29 06:27:25.205 /myreminderapp 200 66ms 0kb Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31`
so what should i do to make it works on the server like on my local