500服务器错误，而部署谷歌应用程序

Question

这是我第一次谷歌应用程序引擎的servlet，我想让它抓取的网站，所以我创建了应用程序引擎使用backgroundThread线程，我的问题是，当我运行在本地主机此应用程序：8888它可以正常工作并完成它应该完成的任务。

Youm7 youm7Crawler = new Youm7(); log.info("start 1"); Thread youm7Thread = ThreadManager.createBackgroundThread(youm7Crawler); log.info("start 2"); log.info("start 3"); youm7Thread.start(); 但一旦我尝试部署它作为服务器，我得到一个错误500服务器，我在日志中得到这个严重错误

`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` 

所以我应该怎么做，使它就像在服务器上在我的本地

Answer 1

GAE的部署可以在两种类型的机器，其中一个是前端（默认值），他们有很多的限制，但他们可以扩展非常快。 其他的人是backends，后端实例没有尽可能多的限制，前端。 由于您的应用程序使用Threds，因此它只能作为后端实例运行。 你需要通过一个XML文件来配置你的应用程序的后端，更多的细节here 你需要将它部署作为后端例如，当你通过谷歌的Eclipse插件上传您的应用程序，窗口有一个选项可以选择前端和后端部署哪些。

-Hope这有助于