TransientFailureException -- > While leasing tasks from pull queue

Question

We are using pull queues with backends in our scenario and our backend tries to lease tasks from our pull queue after some fixed intervals and in case there are no tasks , it does not do anything and in case there are any , those are processed . Yesterday we got this TransientFailureException in our system , which exactly is happening while my servlet is trying to lease task from pull queue . And the exception kept coming until we stopped our backend .

Our code snippet --

{
    Boolean leasedTaskFromFastQueue = true;
    Queue fastQueue = QueueFactory.getQueue("FastQueue");
    Queue slowQueue = QueueFactory.getQueue("SlowQueue");

    List<TaskHandle> tasks = fastQueue.leaseTasks(
        3600, TimeUnit.SECONDS, 1);

    TaskHandle taskHandle = null;

    if(tasks.size() > 0) {

        taskHandle = tasks.get(0);

    }
}

We aret getting error on the line where we lease task from fastQueue , which is a pull queue

<queue>
  <name>FastQueue</name>
  <mode>pull</mode>

</queue>

I am also pasting my error trace , in case that helps

com.google.appengine.api.taskqueue.TransientFailureException:
    at           com.google.appengine.api.taskqueue.QueueApiHelper.translateError(QueueApiHelper.java:79)
    at com.google.appengine.api.taskqueue.QueueApiHelper.translateError(QueueApiHelper.java:139)
    at com.google.appengine.api.taskqueue.QueueApiHelper.makeSyncCall(QueueApiHelper.java:53)
    at com.google.appengine.api.taskqueue.QueueImpl.leaseTasksInternal(QueueImpl.java:709)
    at com.google.appengine.api.taskqueue.QueueImpl.leaseTasks(QueueImpl.java:731)
    at com.implementhit.advancedsupport.server.queue.Backend.doGet(Backend.java:50)
    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$CachedChain.doFilter(ServletHandler.java:1166)
    at com.bitdual.appengine.tools.datastore.server.NamespaceFilter.doFilter(NamespaceFilter.java:96)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:102)
    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$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:249)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$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$RequestRunnable.run(JavaRuntime.java:477)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
    at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
    at java.lang.Thread.run(Thread.java:679)

Answer 1

It happend to us also, TransientFailureException is an internal error that as far as we could see had nothing to do with our code. We ended up by automatically restarting the backend if 50 errors happened in a row.