Github user witgo commented on a diff in the pull request:
https://github.com/apache/spark/pull/12113#discussion_r58711271
--- Diff: core/src/main/scala/org/apache/spark/MapOutputTracker.scala ---
@@ -492,16 +624,51 @@ private[spark] object MapOutputTracker extends
Logging {
} {
objOut.close()
}
- out.toByteArray
+ val arr = out.toByteArray
+ if (minBroadcastSize >= 0 && arr.length >= minBroadcastSize) {
+ // Use broadcast instead.
+ // Important arr(0) is the tag == DIRECT, ignore that while
deserializing !
+ val bcast = broadcastManager.newBroadcast(arr, isLocal)
+ // toByteArray creates copy, so we can reuse out
+ out.reset()
+ out.write(BROADCAST)
+ val oos = new ObjectOutputStream(new GZIPOutputStream(out))
+ oos.writeObject(bcast)
+ oos.close()
+ val outArr = out.toByteArray
+ logInfo("Broadcast mapstatuses size = " + outArr.length + ", actual
size = " + arr.length)
+ (outArr, bcast)
+ } else {
+ (arr, null)
+ }
}
// Opposite of serializeMapStatuses.
def deserializeMapStatuses(bytes: Array[Byte]): Array[MapStatus] = {
- val objIn = new ObjectInputStream(new GZIPInputStream(new
ByteArrayInputStream(bytes)))
- Utils.tryWithSafeFinally {
- objIn.readObject().asInstanceOf[Array[MapStatus]]
- } {
- objIn.close()
+ assert (bytes.length > 0)
+
+ def deserializeObject(arr: Array[Byte], off: Int, len: Int): AnyRef = {
+ val objIn = new ObjectInputStream(new GZIPInputStream(
+ new ByteArrayInputStream(arr, off, len)))
+ Utils.tryWithSafeFinally {
+ objIn.readObject()
+ } {
+ objIn.close()
+ }
+ }
+
+ bytes(0) match {
+ case DIRECT =>
+ deserializeObject(bytes, 1, bytes.length -
1).asInstanceOf[Array[MapStatus]]
+ case BROADCAST =>
+ // deserialize the Broadcast, pull .value array out of it, and
then deserialize that
+ val bcast = deserializeObject(bytes, 1, bytes.length - 1).
+ asInstanceOf[Broadcast[Array[Byte]]]
+ logInfo("Broadcast mapstatuses size = " + bytes.length +
+ ", actual size = " + bcast.value.length)
+ // Important - ignore the DIRECT tag ! Start from offset 1
+ deserializeObject(bcast.value, 1, bcast.value.length -
1).asInstanceOf[Array[MapStatus]]
--- End diff --
Sorry, My English is poor. Judging from the code of
`TorrentBroadcast.readBlocks` and `Dispatcher.MessageLoop`, it is possible that
most of the GetLocations messages are processed in the front of the
UpdateBlockInfo messages.
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