Support for zero-copy file upload/download with `java.nio`

[StephenFlavin]

Describe the feature

Currently it seems that the code specifically deals in on heap ByteBuffers either converting direct to non-direct Buffers or writing to non-direct Buffers when there are more performant and memory efficient zero-copy routes.

Most of the heavy lifting on supporting these off heap/zero copy file transfers are done by the HTTP client and the OS with native support in Java via FileChannel#transferTo and FileChannel#transferFrom to socket channels and similar for SocketChannel#write for DirectByteBuffers.

The specific implementation of this is up to the HTTP client in use (e.g. https://netty.io/4.0/api/io/netty/channel/FileRegion.html) but the option is removed at too high a level for the client specific implementations.

I believe it was done this way to guard against concurrent modification during write ops which I've discussed on https://github.com/aws/aws-sdk-java-v2/pull/3925

Use Case

High frequency efficient read/write ops to S3

Proposed Solution

Don't do any conversion from direct to non-direct ByteBuffers, pass along the File/FileChannel object instead of converting to a ByteBuffer publisher and leave it up to the http client lib to deal with as required.

For Path/File/Filechannel AsyncRequestBody is unsuitable since it's an implementation of SdkPublisher<ByteBuffer>, I think in this case the AsyncRequestBody is just unnecessary and the plain Path/File/Filechannel should be passed on to the http client.

The Netty docs state

If your operating system (or JDK / JRE) does not support zero-copy file transfer, sending a file with FileRegion might fail or yield worse performance. For example, sending a large file doesn't work well in Windows.

In which case this should be possible to disable with a flag passed to the http client when building the S3Client

Other Information

No response

Acknowledgements

• [X] I may be able to implement this feature request
• [ ] This feature might incur a breaking change

AWS Java SDK version used

macOs 13.2.1 (22D68)

JDK version used

openjdk 11.0.16.1 & openjdk 19.0.1

Operating System and version

macOs 13.2.1 (22D68)

[debora-ito]

Thank you @StephenFlavin, this makes sense. We'll review your related PR.

[StephenFlavin]

The related PR would be a precursor to supporting these for put/post with off heap ByteBuffers. As far as I can tell

if (!buffer.hasArray()) {
    buffer = ByteBuffer.wrap(BinaryUtils.copyBytesFrom(buffer));
}

could be removed and it would just work (tested with the netty client) though I didn't want to do it as part of this PR and I haven't had a chance to delve too deep into the netty implementation to make sure it's doing zero copy, I did see a significant performance bump vs inputstream.

The other piece there will be making use of Filechannel.transferTo for put/post but the changes required for that would be more significant since everything currently deals in ByteBuffers.

I've not yet looked at the changes required to the get requests.

[StephenFlavin]

with the pre-cursor PR merged, I've raised the first PR to enable zero-copy transfers via direct byte buffers with AsyncRequestBody comments/thoughts appreciated. I've kept this change small as a minimal effort to support zero-copy in the async S3 client.

[sgammon]

@StephenFlavin / @debora-ito arrived here looking for this feature in the sdk; if you need a user to build and test let me know (i may anyway)

[StephenFlavin]

Hi @sgammon, I've not had any time to work on this as I'm no longer doing such performance sensitive work with S3 though I would like to see the work continued, I may loop back to this in future but feel free to take on a chunk if you fancy it.

• From an upload point of view there's passing FileChannels down the the http client. (would love to see this compared to mapped buffers)
• I hadn't really looked at the download code yet.
• Once these changes were in place I was going to see if IOuring could be used to further improve things (https://github.com/netty/netty-incubator-transport-io_uring)