Confusing backtype.storm.generated.DRPCExecutionException: null

[xiaohu chen <ch...@gmail.com>]

Hi everyone,

    I'm new to storm. Hope anyone can give me some advice on how to debug
this exception. I have a trident topology as well as a DRPC topology
running. The main function is this:

Config conf = *new* Config();

 conf.setMaxSpoutPending(200);

 *if* (args.length == 0) {

 LocalDRPC drpc = *new* LocalDRPC();

 LocalCluster cluster = *new* LocalCluster();

 cluster.submitTopology("topology", conf, *buildTopology*(drpc));

 *for* (*int* i = 0; i < 1000; i++) {

  Thread.*sleep*(100);

  System.*out*.println("DRPC RESULT: " + i

   + drpc.execute("drpc", "Give me similar"));

 }

 }

The program can return result for several times( 7 to be specific, though
the result is an empty list), then it will throw an exception (see below).
It only points to the line "drpc.execute("drpc", "Give me similar"));", but
no further information for what's wrong with the program. Can anyone give
me an advice on how to debug in this situation or any possible reason for
this? I'm using storm-0.9.2-incubating as you can see from the following
error stack trace.

1125463 [Thread-2] WARN  backtype.storm.daemon.drpc - Timeout DRPC request
id: 9 start at 1404977422

1125522 [main] ERROR org.apache.zookeeper.server.NIOServerCnxnFactory -
Thread Thread[main,5,main] died

backtype.storm.generated.DRPCExecutionException: null

at
backtype.storm.daemon.drpc$service_handler$reify__5501.execute(drpc.clj:95)
~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
~[na:1.6.0_65]

at sun.reflect.NativeMethodAccessorImpl.invoke(
NativeMethodAccessorImpl.java:39) ~[na:1.6.0_65]

at sun.reflect.DelegatingMethodAccessorImpl.invoke(
DelegatingMethodAccessorImpl.java:25) ~[na:1.6.0_65]

at java.lang.reflect.Method.invoke(Method.java:597) ~[na:1.6.0_65]

at clojure.lang.Reflector.invokeMatchingMethod(Reflector.java:93)
~[clojure-1.5.1.jar:na]

at clojure.lang.Reflector.invokeInstanceMethod(Reflector.java:28)
~[clojure-1.5.1.jar:na]

at backtype.storm.LocalDRPC$_execute.invoke(LocalDRPC.clj:35)
~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]

at backtype.storm.LocalDRPC.execute(Unknown Source)
~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]

at hashtags.HashtagTopology.main(MyTopology.java:158) ~[classes/:na]