Clint Heath created MAPREDUCE-4464: -------------------------------------- Summary: Reduce tasks failing with NullPointerException in ConcurrentHashMap.get() Key: MAPREDUCE-4464 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4464 Project: Hadoop Map/Reduce Issue Type: Bug Components: task Affects Versions: 1.0.0 Reporter: Clint Heath Priority: Minor
If DNS does not resolve hostnames properly, reduce tasks can fail with a very misleading exception. as per my peer Ahmed's diagnosis: In ReduceTask, it seems that event.getTaskTrackerHttp() returns a malformed URI, and so host from: {code} String host = u.getHost(); {code} is evaluated to null and the NullPointerException is thrown afterwards in the ConcurrentHashMap. I have written a patch to check for a null hostname condition when getHost is called in the getMapCompletionEvents method and print an intelligible warning message rather than suppressing it until later when it becomes confusing and misleading. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira