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SPARK-4454 Fix race condition in DAGScheduler #3345

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SPARK-4454 Fix race condition in DAGScheduler #3345

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17 changes: 9 additions & 8 deletions core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -193,15 +193,16 @@ class DAGScheduler(
eventProcessActor ! TaskSetFailed(taskSet, reason)
}

private def getCacheLocs(rdd: RDD[_]): Array[Seq[TaskLocation]] = {
if (!cacheLocs.contains(rdd.id)) {
val blockIds = rdd.partitions.indices.map(index => RDDBlockId(rdd.id, index)).toArray[BlockId]
val locs = BlockManager.blockIdsToBlockManagers(blockIds, env, blockManagerMaster)
cacheLocs(rdd.id) = blockIds.map { id =>
locs.getOrElse(id, Nil).map(bm => TaskLocation(bm.host, bm.executorId))
}
private def getLocs(rdd: RDD[_]): Array[Seq[TaskLocation]] = {
val blockIds = rdd.partitions.indices.map(index => RDDBlockId(rdd.id, index)).toArray[BlockId]
val locs = BlockManager.blockIdsToBlockManagers(blockIds, env, blockManagerMaster)
blockIds.map { id =>
locs.getOrElse(id, Nil).map(bm => TaskLocation(bm.host, bm.executorId))
}
cacheLocs(rdd.id)
}

private def getCacheLocs(rdd: RDD[_]): Array[Seq[TaskLocation]] = {
cacheLocs.getOrElseUpdate(rdd.id,getLocs(rdd))
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@srowen srowen Nov 18, 2014

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Hm, is this actually thread-safe either? It's not a concurrent Map. Even if it is, I'm not clear that it stops many values for being cached and computed for an ID, but if that's cheap and they're immutable, that could be fine.

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@JoshRosen JoshRosen Dec 24, 2014

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Even if this was a concurrent map, I'm not sure that getOrElseUpdate would be thread-safe (surprisingly!):

https://issues.scala-lang.org/browse/SI-7943

}

private def clearCacheLocs() {
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