Hong Tang added a comment - 23/Jul/10 00:50 It seems that StatsCollectorThread is still active when we call "clusterStatlisteners.clear();" from "Statistics.shutdown()". A simple fix is to replace "clusterStatlisteners.clear();" with "lusterStatlisteners = new ArrayList<StatListener<ClusterStats>>()". While we are at it, we probably should also fix the same problem with jobStatListeners.

Hong Tang added a comment - 23/Jul/10 23:10 Trivial patch that uses CopyOnWriteArrayList to avoid concurrent modification. No unit test included as it is hard to reproduce the synchronization bug through unit tests.

Hong Tang added a comment - 07/Aug/10 00:19 retry hudson

Ranjit Mathew added a comment - 09/Aug/10 11:02 +1 for the patch.

Hong Tang added a comment - 10/Aug/10 04:42 test-patch output: [exec] -1 overall. [exec] [exec] +1 @author. The patch does not contain any @author tags. [exec] [exec] -1 tests included. The patch doesn't appear to include any new or modified tests. [exec] Please justify why no new tests are needed for this patch. [exec] Also please list what manual steps were performed to verify this patch. [exec] [exec] +1 javadoc. The javadoc tool did not generate any warning messages. [exec] [exec] +1 javac. The applied patch does not increase the total number of javac compiler warnings. [exec] [exec] +1 findbugs. The patch does not introduce any new Findbugs warnings. [exec] [exec] +1 release audit. The applied patch does not increase the total number of release audit warnings. -1 tests included The patch fixes a concurrency bug, and is hard to write unit test to cover. The patch is tested with real benchmark runs and has shown to be effective.

Chris Douglas added a comment - 12/Aug/10 08:49 +1 I committed this. Thanks, Hong!

Hudson added a comment - 29/Oct/10 02:03 Integrated in Hadoop-Mapreduce-trunk-Commit #523 (See https://hudson.apache.org/hudson/job/Hadoop-Mapreduce-trunk-Commit/523/ )