Github user massie commented on a diff in the pull request:
https://github.com/apache/spark/pull/6423#discussion_r32076483
--- Diff:
core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala ---
@@ -33,17 +34,54 @@ private[spark] class HashShuffleReader[K, C](
"Hash shuffle currently only supports fetching one partition")
private val dep = handle.dependency
+ private val blockManager = SparkEnv.get.blockManager
/** Read the combined key-values for this reduce task */
override def read(): Iterator[Product2[K, C]] = {
+ val blockStreams = BlockStoreShuffleFetcher.fetchBlockStreams(
+ handle.shuffleId, startPartition, context)
+
+ // Wrap the streams for compression based on configuration
+ val wrappedStreams = blockStreams.map { case (blockId, inputStream) =>
+ blockManager.wrapForCompression(blockId, inputStream)
+ }
+
val ser = Serializer.getSerializer(dep.serializer)
- val iter = BlockStoreShuffleFetcher.fetch(handle.shuffleId,
startPartition, context, ser)
+ val serializerInstance = ser.newInstance()
+
+ // Create a key/value iterator for each stream
+ val recordIterator = wrappedStreams.flatMap { wrappedStream =>
+ val kvIter =
serializerInstance.deserializeStream(wrappedStream).asKeyValueIterator
+ CompletionIterator[(Any, Any), Iterator[(Any, Any)]](kvIter, {
+ // Close the stream once all the records have been read from it to
free underlying
+ // ManagedBuffer as soon as possible. Note that in case of task
failure, the task's
+ // TaskCompletionListener will make sure this is released.
+ wrappedStream.close()
--- End diff --
@kayousterhout Actually, I wasn't aware that `asKeyValueIterator` returned
a `NextIterator` which closed the underlying input stream. Thanks for pointing
that out to me.
The `BufferReleasingInputStream.close()` is idempotent so it doesn't hurt
to call it twice (I've also updated the unit tests to assure this is the case).
The Parquet Shuffle Manager I'm writing doesn't use any Spark `Serializer` so
that's why I noticed I needed to `close()` in the reader.
I'll remove the `CompletionIterator` unless you think otherwise.
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