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From Aapo Kyrola <>
Subject Fatal exception sometimes happening
Date Fri, 30 Sep 2011 23:08:30 GMT

occasionally (maybe one time in four), my giraph run fails because of the below RuntimeException.
According to code, it should never happen:

	      if (msgMap == null) { // should never happen after constructor
            throw new RuntimeException(
                "sendMessage: msgMap did not exist for " + addr +
                " for vertex " + destVertex);

This happens during superstep 1 (second superstep).  My application actually *adds* edges
on superstep 1
(to make every out-edge also an in-edge of the destination), but since I am running only on
3 workers,
I am surprised if every worker would not had been registered in the RPC layer initially.

One hypothesis is that Hadoop does something funny, because one of my server was under heavy
load. Maybe Hadoop launched another worker to replace a slow worker? Can it happen?

java.lang.RuntimeException: sendMessage: msgMap did not exist for [hostname]
for vertex 875713
        at org.apache.giraph.comm.BasicRPCCommunications.sendMessageReq(
        at org.apache.giraph.graph.BasicVertex.sendMsg(
        at edu.cmu.selectlab.BP.BinaryBPVertex.compute(
        at org.apache.hadoop.mapred.MapTask.runNewMapper(
        at org.apache.hadoop.mapred.Child$
        at Method)
        at org.apache.hadoop.mapred.Child.main(

Aapo Kyrola
Ph.D. student,

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