Testcontainers - Localstack - S3 - Virtual Host Addressing Not Working

Been trying to get Testcontainers to work with virtual host addressing for the last couple of days as path style addressing is on the way out. But for the life of me I can't get the AWS SDK V2 for Java to work with Testcontainers.LocalStackContainer.

My extended Testcontainer looks like this:

public class LocalStackContainerExtended extends LocalStackContainer {
   public static final String BUCKET_NAME = "testBucket";
   // Need to include bucket in network alias as we're not running any DNS resolver in test
   public static final String LOCALSTACK_NETWORK_ALIAS = BUCKET_NAME + "." + "localstack";

   public LocalStackContainerExtended(DockerImageName dockerImageName) {
       super(dockerImageName);

       withServices(Service.S3);
       withNetworkAliases(LOCALSTACK_NETWORK_ALIAS);
   }

   @Override
   public void start() {
       super.start();
       try {
           execInContainer("awslocal", "s3api", "create-bucket", "--bucket", BUCKET_NAME);
       } catch (Exception e) {
           throw new RuntimeException();
    }
}

AWS SDK client config for the component that needs to talk with Localstack:

@Bean
// AwsConfigService collection class of aws override values
public S3Client getS3Client(AwsConfigService awsConfigService) {
    S3ClientBuilder builder = S3Client.builder()
        .region(awsConfigService.getRegion());

    return awsConfigService.getOverrideEndpoint()
        .map(URI::create)
        .map(builder::endpointOverride)
        .orElse(builder).build();
}

Testcontainer setup for the component:

public class AppContainer extends GenericContainer<AppContainer>{
   ...
   public void setLocalstackConfig(LocalStackContainerExtended localstack) {
      withEnv("awsConfigService.region", localstack.getRegion());
      String overrideEndpoint = String.format("http://%s:%s", LOCALSTACK_NETWORK_ALIAS,"4566");
      withEnv("awsConfigService.override.endpoint", overrideEndpoint);
   }
   ...
}

But when running tests between the the client and Testcontainer I always get the following error:

> The specified bucket does not exist (Service: S3, Status Code: 404, Request ID: 7a62c49f-347e-4fc4-9331-6e8eEXAMPLE, Extended Request ID: MzRISOwyjmnupEEE949DD2EAF7F477/JypPGXLh0OVFGcJaaO3KW/hRAqKOpIEEp

What have I miss-configured or what is missing?

It might be that LocalStack is not recognising your incoming request as a Virtual Host addressed one.
Could try replacing the network alias with the followings?

public class LocalStackContainerExtended extends LocalStackContainer {
   public static final String BUCKET_NAME = "testBucket";
   // Need to include bucket in network alias as we're not running any DNS resolver in test
   public static final String LOCALSTACK_S3_NETWORK_ALIAS = "s3.localhost.localstack.cloud";
   // You need to also include an alias for the to-be-created bucket
   public static final String BUCKET_LOCALSTACK_S3_NETWORK_ALIAS = BUCKET_NAME + "." + LOCALSTACK_S3_NETWORK_ALIAS

   public LocalStackContainerExtended(DockerImageName dockerImageName) {
       super(dockerImageName);

       withServices(Service.S3);
       withNetworkAliases(LOCALSTACK_S3_NETWORK_ALIAS);
       withNetworkAliases(BUCKET_LOCALSTACK_S3_NETWORK_ALIAS);
   }

   @Override
   public void start() {
       super.start();
       try {
           execInContainer("awslocal", "s3api", "create-bucket", "--bucket", BUCKET_NAME);
       } catch (Exception e) {
           throw new RuntimeException();
    }
}

When receiving a request with this host, S3 should recognise the request and parse it properly. What is happening right now is that it does not recognise the bucket in your request, as it does not extract it from the host because it does not follow the pattern.

More informations about virtual host addressing in LocalStack: https://docs.localstack.cloud/user-guide/aws/s3/#getting-started

You then need to also configure the client to use the right endpoint. Your S3 client will take care of prefixing your endpoint with the bucket name when targeting S3, so you need to use LOCALSTACK_S3_NETWORK_ALIAS as the overrideEndpoint (but beware, only for the client targeting S3!). Most other clients can use the endpoint localstack:4566 pointing to your container.

public class AppContainer extends GenericContainer<AppContainer>{
   ...
   public void setLocalstackConfig(LocalStackContainerExtended localstack) {
      withEnv("awsConfigService.region", localstack.getRegion());
      String overrideEndpoint = String.format("http://%s:%s", LOCALSTACK_S3_NETWORK_ALIAS,"4566");
      withEnv("awsConfigService.override.endpoint", overrideEndpoint);
   }
   ...
}