GitHub user viirya opened a pull request: https://github.com/apache/spark/pull/13211
[SPARK-15430][SQL] Fix potential ConcurrentModificationException for ListAccumulator ## What changes were proposed in this pull request? In `ListAccumulator` we create an unmodifiable view for underlying list. However, it doesn't prevent the underlying to be modified further. So as we access the unmodifiable list, the underlying list can be modified in the same time. It could cause `java.util.ConcurrentModificationException`. We can observe such exception in recent tests. To fix it, we can copy a list of the underlying list and then create the unmodifiable view of this list instead. ## How was this patch tested? The exception might be difficult to test. You can merge this pull request into a Git repository by running: $ git pull https://github.com/viirya/spark-1 fix-concurrentmodify Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/13211.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #13211 ---- commit 4d97bf093f4f4d41cf530a4c7464532635c2b3fe Author: Liang-Chi Hsieh <sim...@tw.ibm.com> Date: 2016-05-20T04:15:49Z Fix potential ConcurrentModificationException for ListAccumulator. ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. --- --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org