We are seeing something that looks a lot like a regression from spark 1.2. When we run jobs with multiple threads, we have a crash somewhere inside getPreferredLocations, as was fixed in SPARK-4454. Except now it's inside org.apache.spark.MapOutputTrackerMaster.getLocationsWithLargestOutputs instead of DAGScheduler directly.
I tried Spark 1.2 post-SPARK-4454 (before this patch it's only slightly flaky), 1.4.1, and 1.5.2 and all are fine. 1.6.0 immediately crashes on our threaded test case, though once in a while it passes. The stack trace is huge, but starts like this: Caused by: java.lang.NullPointerException: null at org.apache.spark.MapOutputTrackerMaster.getLocationsWithLargestOutputs(MapOutputTracker.scala:406) at org.apache.spark.MapOutputTrackerMaster.getPreferredLocationsForShuffle(MapOutputTracker.scala:366) at org.apache.spark.rdd.ShuffledRDD.getPreferredLocations(ShuffledRDD.scala:92) at org.apache.spark.rdd.RDD$$anonfun$preferredLocations$2.apply(RDD.scala:257) at org.apache.spark.rdd.RDD$$anonfun$preferredLocations$2.apply(RDD.scala:257) at scala.Option.getOrElse(Option.scala:120) at org.apache.spark.rdd.RDD.preferredLocations(RDD.scala:256) at org.apache.spark.scheduler.DAGScheduler.org $apache$spark$scheduler$DAGScheduler$$getPreferredLocsInternal(DAGScheduler.scala:1545) The full trace is available here: https://gist.github.com/andy256/97611f19924bbf65cf49 Does this ring any bells? I will attempt to nail down the commit with git bisect next. Thanks -Andy
