Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/3345#discussion_r20502430
--- 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 --
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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