[MAPREDUCE-6198] NPE from JobTracker#resolveAndAddToTopology in MR1 cause initJob and heartbeat failure.

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.3.0
• Component/s: mrv1
• Hadoop Flags: Reviewed
• Assignee: Zhihai Xu
• Reporter: Zhihai Xu
• Created: 18/Dec/14 01:29
• Updated: 19/Dec/14 21:45
• Resolved: 19/Dec/14 19:40

Description

NPE from JobTracker#resolveAndAddToTopology in MR1 cause initJob and heartbeat failure. The NPE is caused by dnsToSwitchMapping.resolve return null at the following:

    List <String> rNameList = dnsToSwitchMapping.resolve(tmpList);
    String rName = rNameList.get(0);

I check the code in MR2, MR2 handle it correctly in coreResolve of RackResolver.java

    List <String> rNameList = dnsToSwitchMapping.resolve(tmpList);
    String rName = null;
    if (rNameList == null || rNameList.get(0) == null) {
      rName = NetworkTopology.DEFAULT_RACK;
      LOG.info("Couldn't resolve " + hostName + ". Falling back to "
          + NetworkTopology.DEFAULT_RACK);
    } else {
      rName = rNameList.get(0);
      LOG.info("Resolved " + hostName + " to " + rName);
    }

We should do the same in MR1, if dnsToSwitchMapping.resolve return null, use NetworkTopology.DEFAULT_RACK.