UploadPartResponse seems to hold a reference to the content of the part, even after stream is closed

[jakobmerrild]

Describe the bug

When using the S3Client to uploadPart, the returned UploadPartResponse seems to hold a reference to the content of the part, causing memory build up over time

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

The UploadPartResponse should only hold information related to the actual response as described here: https://docs.aws.amazon.com/AmazonS3/latest/API/API_UploadPart.html#API_UploadPart_ResponseElements

Current Behavior

When uploading multiple parts in sequence and keeping the UploadPartResponse in memory to be used later to complete the multi part upload we see a build up of memory over time. Upon inspection of a heap dump we noticed that the UploadPartResponse had a memory footprint roughly equal to our part size, which was unexpected.

It seems that UploadPartResponse holds a reference to an underlying sdkHttpResponse which in turn holds a content reference which is an AbortableInputStream the size of the part.

Reproduction Steps

Our code is written in Scala, but to the best of my knowledge this Java code serves as a minimum example

import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.*;
import software.amazon.awssdk.core.sync.RequestBody;

import java.io.ByteArrayInputStream;
import java.util.ArrayList;
import java.util.List;

public class S3MultipartUploadFullExample {
    public static void main(String[] args) {
        S3Client s3 = S3Client.create();
        String bucket = "your-bucket";
        String key = "your-key";
        byte[] chunk = new byte[50 * 1024 * 1024]; // 50MB chunk

        CreateMultipartUploadRequest createRequest = CreateMultipartUploadRequest.builder()
                .bucket(bucket)
                .key(key)
                .build();
        CreateMultipartUploadResponse initiateResult = s3.createMultipartUpload(createRequest);

        // We need to hold the responses so we can complete the multi part upload later
        List<UploadPartResponse> partUploadResponses = new ArrayList<>();
        for (int i = 0; i < 100; i++) {
            try (ByteArrayInputStream is = new ByteArrayInputStream(chunk)) {
                int partNumber = i + 1;
                UploadPartRequest uploadPartRequest = UploadPartRequest.builder()
                        .bucket(bucket)
                        .key(key)
                        .uploadId(initiateResult.uploadId())
                        .partNumber(partNumber)
                        .contentLength(chunk.length)
                        .build();
                UploadPartResponse response = s3.uploadPart(uploadPartRequest, RequestBody.fromInputStream(is, chunk.length));
                partUploadResponses.add(response);
            }
        }
        // At this point the heap has grown to 100 * 50MB ~ 5GB because each UploadPartResponse
        // in partUploadResponses holds a reference to a stream with the content
        
        List<CompletedPart> completedParts = new ArrayList<>();
        for (int i = 0; i < partUploadResponses.size(); i++) {
            completedParts.add(CompletedPart.builder()
                    .partNumber(i + 1)
                    .eTag(partUploadResponses.get(i).eTag())
                    .build());
        }

        CompletedMultipartUpload completedMultipartUpload = CompletedMultipartUpload.builder()
                .parts(completedParts)
                .build();
        CompleteMultipartUploadRequest completeRequest = CompleteMultipartUploadRequest.builder()
                .bucket(bucket)
                .key(key)
                .uploadId(initiateResult.uploadId())
                .multipartUpload(completedMultipartUpload)
                .build();
        CompleteMultipartUploadResponse completeResponse = s3.completeMultipartUpload(completeRequest);

        System.out.println("Multipart upload completed: " + completeResponse.key());
        s3.close();
    }
}

Possible Solution

No response

Additional Information/Context

No response

AWS Java SDK version used

2.31.78

JDK version used

Picked up JAVA_TOOL_OPTIONS: -XX:UseSVE=0 openjdk 21.0.7 2025-04-15 OpenJDK Runtime Environment (build 21.0.7+6-alpine-r0) OpenJDK 64-Bit Server VM (build 21.0.7+6-alpine-r0, mixed mode, sharing)

Operating System and version

Linux Alpine 3.21.3