S3AsyncClient doesn't respect chunkedEncodingEnabled(false)

[vladykin]

Describe the bug

Some third-party S3 implementations don't support chunked encoding and require setting S3Configuration.builder().chunkedEncodingEnabled(false). Example:
https://www.alibabacloud.com/help/en/oss/developer-reference/use-amazon-s3-sdks-to-access-oss

This config tweak works with S3Client, but is apparently ignored by the S3AsyncClient. Despite having .chunkedEncodingEnabled(false), the S3AsyncClient still uses chunked encoding.

Regression Issue

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

Expected Behavior

We'd expect S3AsyncClient to behave similarly to S3Client, i.e. stop using chunked encoding when .chunkedEncodingEnabled(false) is specified.

Current Behavior

S3AsyncClient uses chunked encoding despite .chunkedEncodingEnabled(false)

Reproduction Steps

Here's a unit test demonstrating the behavior of both S3Client and S3AsyncClient:

import static com.github.tomakehurst.wiremock.client.WireMock.matching;
import static com.github.tomakehurst.wiremock.client.WireMock.ok;
import static com.github.tomakehurst.wiremock.client.WireMock.put;
import static com.github.tomakehurst.wiremock.client.WireMock.putRequestedFor;
import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;

import com.github.tomakehurst.wiremock.WireMockServer;
import com.github.tomakehurst.wiremock.matching.UrlPattern;
import java.net.URI;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import software.amazon.awssdk.auth.credentials.AwsBasicCredentials;
import software.amazon.awssdk.auth.credentials.StaticCredentialsProvider;
import software.amazon.awssdk.core.async.AsyncRequestBody;
import software.amazon.awssdk.core.sync.RequestBody;
import software.amazon.awssdk.services.s3.S3AsyncClient;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.S3Configuration;
import software.amazon.awssdk.services.s3.model.PutObjectRequest;

public class S3ChunkedEncodingTest {

  private static WireMockServer server;

  @BeforeAll
  static void beforeAll() {
    server = new WireMockServer(wireMockConfig().dynamicPort());
    server.stubFor(put(UrlPattern.ANY).willReturn(ok()));
    server.start();
  }

  @AfterAll
  static void afterAll() {
    if (server != null) {
      server.stop();
    }
  }

  @BeforeEach
  void setUp() {
    server.resetRequests();
  }

  @Test
  void syncClientChunkedEncodingEnabled() {
    try (S3Client client = buildS3Client(buildS3Configuration(true))) {
      client.putObject(PutObjectRequest.builder().bucket("bucket").key("foobar").build(), RequestBody.empty());
    }
    server.verify(putRequestedFor(UrlPattern.ANY)
        .withHeader("Content-Encoding", matching("aws-chunked")));
  }

  @Test
  void syncClientChunkedEncodingDisabled() {
    try (S3Client client = buildS3Client(buildS3Configuration(false))) {
      client.putObject(PutObjectRequest.builder().bucket("bucket").key("foobar").build(), RequestBody.empty());
    }
    server.verify(putRequestedFor(UrlPattern.ANY)
        .withoutHeader("Content-Encoding"));
  }

  @Test
  void asyncClientChunkedEncodingEnabled() {
    try (S3AsyncClient client = buildS3AsyncClient(buildS3Configuration(true))) {
      client.putObject(PutObjectRequest.builder().bucket("bucket").key("foobar").build(), AsyncRequestBody.empty()).join();
    }
    server.verify(putRequestedFor(UrlPattern.ANY)
        .withHeader("Content-Encoding", matching("aws-chunked")));
  }

  @Test
  void asyncClientChunkedEncodingDisabled() {
    // Turns out S3AsyncClient doesn't respect the property disabling chunked encoding. This test will fail.
    try (S3AsyncClient client = buildS3AsyncClient(buildS3Configuration(false))) {
      client.putObject(PutObjectRequest.builder().bucket("bucket").key("foobar").build(), AsyncRequestBody.empty()).join();
    }
    server.verify(putRequestedFor(UrlPattern.ANY)
        .withoutHeader("Content-Encoding"));
  }

  @Test
  void asyncCrtClientChunkedEncodingEnabled() {
    // CRT always uses chunked encoding, there's no property to disable it. See https://github.com/aws/aws-sdk-java-v2/issues/4806
    try (S3AsyncClient client = S3AsyncClient.crtBuilder()
        .credentialsProvider(dummyCredentials())
        .endpointOverride(URI.create(server.baseUrl()))
        .build()) {
      client.putObject(PutObjectRequest.builder().bucket("bucket").key("foobar").build(), AsyncRequestBody.empty()).join();
    }
    server.verify(putRequestedFor(UrlPattern.ANY)
        .withHeader("Content-Encoding", matching("aws-chunked")));
  }


  private static S3Configuration buildS3Configuration(boolean chunkedEncoding) {
    return S3Configuration.builder()
        .chunkedEncodingEnabled(chunkedEncoding)
        .build();
  }

  private static S3Client buildS3Client(S3Configuration s3config) {
    return S3Client.builder()
        .serviceConfiguration(s3config)
        .credentialsProvider(dummyCredentials())
        .endpointOverride(URI.create(server.baseUrl()))
        .build();
  }

  private static S3AsyncClient buildS3AsyncClient(S3Configuration s3Config) {
    return S3AsyncClient.builder()
        .serviceConfiguration(s3Config)
        .credentialsProvider(dummyCredentials())
        .endpointOverride(URI.create(server.baseUrl()))
        .build();
  }

  private static StaticCredentialsProvider dummyCredentials() {
    return StaticCredentialsProvider.create(AwsBasicCredentials.create("dummy", "dummy"));
  }
}

Possible Solution

No response

Additional Information/Context

No response

AWS Java SDK version used

2.30.36

JDK version used

openjdk version "17.0.16" 2025-07-15 LTS

Operating System and version

Linux, kernel 6.12.31

[bhoradc]

Hello @vladykin,

Thank you for reporting the issue. I see similar behavior connecting to AWS S3 as well. It is obserrved post S3 default integrity protection changes that were released in SDK version 2.30.0. I believe the SDK has to send the Content-Encoding: aws-chunked header when it does the default CRC checksum, therefore overlooking the chunkedEncodingEnabled(false) setting for Async operation. But I will dig deeper to determine if this is an intended behavior change or something that needs to be fixed.

As a temporary workaround, you could disable the default integrity protection as explained in this announcement.

System.setProperty(SdkSystemSetting.AWS_REQUEST_CHECKSUM_CALCULATION.property(),
"WHEN_REQUIRED");

Regards,
Chaitanya

[vladykin]

@bhoradc, thanks, I confirm that

System.setProperty(SdkSystemSetting.AWS_REQUEST_CHECKSUM_CALCULATION.property(),
"WHEN_REQUIRED");

as well as

clientBuilder.requestChecksumCalculation(RequestChecksumCalculation.WHEN_REQUIRED)

disable sending Content-Encoding: aws-chunked header for S3AsyncClient (both default and CRT one) in my test case.
But surprisingly not for the S3Client. For S3Client, apparently, .chunkedEncodingEnabled(true) takes precedence.

I also tried the deprecated S3Configuration.Builder.checksumValidationEnabled(false). It also disables sending Content-Encoding: aws-chunked for S3AsyncClient. But again, not for S3Client. So, another inconsistency between sync and async clients.

[bhoradc]

Hi @vladykin,

Thanks for providing additonal details on this.

For S3Client, apparently, .chunkedEncodingEnabled(true) takes precedence.

I do not see this happening with AWS S3 connection. With .chunkedEncodingEnabled(true), it does not take precedence over the request_checksum_calculation set to WHEN_REQUIRED.

I also tried the deprecated S3Configuration.Builder.checksumValidationEnabled(false). It also disables sending Content-Encoding: aws-chunked for S3AsyncClient. But again, not for S3Client.

checksumValidationEnabled(false) disables sending Content-Encoding: aws-chunked for both S3AsyncClient and S3Client.

Starting v2.30.0, the checksumValidationEnabled() has been replaced by S3ClientBuilder#requestChecksumCalculation(RequestChecksumCalculation), which does work in both the sync and async clients.

Here's the code sample I have used to test these scenarios.

ChunkedEncodingTest.java

import software.amazon.awssdk.core.async.AsyncRequestBody;
import software.amazon.awssdk.core.sync.RequestBody;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3AsyncClient;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.S3Configuration;
import software.amazon.awssdk.services.s3.model.PutObjectRequest;
import java.nio.charset.StandardCharsets;

public class ChunkedEncodingTest {
    
    public static void main(String[] args) {
//        System.setProperty(SdkSystemSetting.AWS_REQUEST_CHECKSUM_CALCULATION.property(),
//                "WHEN_REQUIRED");
       //testSyncClient();
       testAsyncClient();
    }
    
    private static void testSyncClient() {
        S3Configuration s3Config = S3Configuration.builder()
                .chunkedEncodingEnabled(false)
                //.checksumValidationEnabled(false)
                .build();
        
        System.out.println("S3Client chunkedEncodingEnabled value: " + s3Config.chunkedEncodingEnabled());
        
        S3Client syncClient = S3Client.builder()
                .region(Region.US_EAST_1)
                .serviceConfiguration(s3Config)
                //.requestChecksumCalculation(RequestChecksumCalculation.WHEN_REQUIRED)
                .build();

        PutObjectRequest putRequest = PutObjectRequest.builder()
                .bucket("i***6273")
                .key("test-***")
                .build();

        try {
            syncClient.putObject(putRequest, RequestBody.fromString("Test content for chunked encoding"));
            System.out.println("S3Client: PUT operation completed with small payload");
        } catch (Exception e) {
            System.out.println("S3Client small payload error: " + e.getMessage());
        }

        String largeContent = "x".repeat(10000);
        try {
            syncClient.putObject(putRequest.toBuilder().key("test-object-large").build(), 
                    RequestBody.fromString(largeContent));
            System.out.println("S3Client: PUT operation completed with large payload");
        } catch (Exception e) {
            System.out.println("S3Client error: " + e.getMessage());
        } finally {
            syncClient.close();
        }
    }
    
    private static void testAsyncClient() {
        S3Configuration s3Config = S3Configuration.builder()
                //.chunkedEncodingEnabled(false)
                .build();
        
        System.out.println("Default chunkedEncodingEnabled value: " + s3Config.chunkedEncodingEnabled());
        
        S3AsyncClient asyncClient = S3AsyncClient.builder()
                .region(Region.US_EAST_1)
                .serviceConfiguration(s3Config)
                //.requestChecksumCalculation(RequestChecksumCalculation.WHEN_REQUIRED)
                .build();

        PutObjectRequest putRequest = PutObjectRequest.builder()
                .bucket("i***6273")
                .key("test-***")
                .build();

        try {
            asyncClient.putObject(putRequest, AsyncRequestBody.fromString("Test content for chunked encoding"))
                    .whenComplete((response, throwable) -> {
                        if (throwable != null) {
                            System.out.println("S3AsyncClient fromString error: " + throwable.getMessage());
                        } else {
                            System.out.println("S3AsyncClient fromString: PUT operation completed");
                        }
                    }).join();
        } catch (Exception e) {
            System.out.println("S3AsyncClient fromString error: " + e.getMessage());
        }
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>V2_chunkedEncodingEnabled_6387</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>22</maven.compiler.source>
        <maven.compiler.target>22</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-bom</artifactId>
            <version>2.19.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>software.amazon.awssdk</groupId>
            <artifactId>s3</artifactId>
            <version>2.33.1</version>
<!--            <version>2.29.52</version>-->
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-slf4j2-impl</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-1.2-api</artifactId>
        </dependency>
    </dependencies>
</project>

Regards,
Chaitanya