Github user viper-kun commented on a diff in the pull request: https://github.com/apache/spark/pull/2471#discussion_r18739911 --- Diff: core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala --- @@ -195,22 +241,68 @@ private[history] class FsHistoryProvider(conf: SparkConf) extends ApplicationHis } } - val newIterator = logInfos.iterator.buffered - val oldIterator = applications.values.iterator.buffered - while (newIterator.hasNext && oldIterator.hasNext) { - if (newIterator.head.endTime > oldIterator.head.endTime) { - addIfAbsent(newIterator.next) - } else { - addIfAbsent(oldIterator.next) + applications.synchronized { --- End diff -- I think there is a need for the two tasks to never run concurrently. if the order is: 1. check task get applications 2. clean task get applications 3. clean task get result, and replace applications 4. check task get result, and replace applications then clean task result is covered by check result. use a ScheduledExecutorService with a single worker thread is a good way to solve it.
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