Github user squito commented on a diff in the pull request:
https://github.com/apache/spark/pull/16989#discussion_r165178844
--- Diff:
common/network-shuffle/src/main/java/org/apache/spark/network/shuffle/OneForOneBlockFetcher.java
---
@@ -126,4 +150,38 @@ private void failRemainingBlocks(String[]
failedBlockIds, Throwable e) {
}
}
}
+
+ private class DownloadCallback implements StreamCallback {
+
+ private WritableByteChannel channel = null;
+ private File targetFile = null;
+ private int chunkIndex;
+
+ public DownloadCallback(File targetFile, int chunkIndex) throws
IOException {
+ this.targetFile = targetFile;
+ this.channel = Channels.newChannel(new FileOutputStream(targetFile));
+ this.chunkIndex = chunkIndex;
+ }
+
+ @Override
+ public void onData(String streamId, ByteBuffer buf) throws IOException
{
+ channel.write(buf);
--- End diff --
I am super-late on reviewing this, apologies, just asking questions for my
own understanding, and to consider possible future improvements -- this won't
do a zero-copy transfer, will it? That ByteBuffer is still in user space?
From my understanding, we'd need to do special handling to use netty's
`spliceTo` when possible:
https://stackoverflow.com/questions/30322957/is-there-transferfrom-like-functionality-in-netty-for-zero-copy
but I'm still working on putting all the pieces together here and
admittedly this is out of my area of expertise
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