Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/3345#discussion_r22241380
--- Diff: core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
---
@@ -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))
--- End diff --
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
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