Github user JoshRosen commented on a diff in the pull request: https://github.com/apache/spark/pull/14412#discussion_r101447797 --- Diff: core/src/main/scala/org/apache/spark/storage/BlockManagerMasterEndpoint.scala --- @@ -195,17 +198,39 @@ class BlockManagerMasterEndpoint( // Remove it from blockManagerInfo and remove all the blocks. blockManagerInfo.remove(blockManagerId) + val iterator = info.blocks.keySet.iterator while (iterator.hasNext) { val blockId = iterator.next val locations = blockLocations.get(blockId) locations -= blockManagerId if (locations.size == 0) { blockLocations.remove(blockId) + logWarning(s"No more replicas available for $blockId !") + } else if (proactivelyReplicate && (blockId.isRDD || blockId.isInstanceOf[TestBlockId])) { + // only RDD blocks store data that users explicitly cache so we only need to proactively + // replicate RDD blocks + // broadcast related blocks exist on all executors, so we don't worry about them + // we also need to replicate this behavior for test blocks for unit tests + // we send a message to a randomly chosen executor location to replicate block + // assuming single executor failure, we find out how many replicas existed before failure + val maxReplicas = locations.size + 1 + + val i = (new Random(blockId.hashCode)).nextInt(locations.size) + val blockLocations = locations.toSeq + val candidateBMId = blockLocations(i) + val blockManager = blockManagerInfo.get(candidateBMId) + if(blockManager.isDefined) { + val remainingLocations = locations.toSeq.filter(bm => bm != candidateBMId) --- End diff -- Is it possible for this list to be empty in certain corner-cases? What happens if `ReplicateBlock` is called with an empty set of locations? Is it just a no-op in that case?
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