The lambda execution is not suspending and the lambda container has no port exposed when running a java 11 lambda with the latest localstack docker image by docker-compose with the environment variable LAMBDA_JAVA_OPTS=-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=_debug_port_
    
It works fine for java8 runtime executions.

Docker command:

> localstack_1  | 2020-01-26T12:42:04:INFO:localstack.services.awslambda.lambda_executors: Running lambda cmd: CONTAINER_ID="$(docker create -i   -e ENV="$ENV" -e DOCKER_LAMBDA_USE_STDIN="$DOCKER_LAMBDA_USE_STDIN" -e HOSTNAME="$HOSTNAME" -e LOCALSTACK_HOSTNAME="$LOCALSTACK_HOSTNAME" -e AWS_LAMBDA_FUNCTION_TIMEOUT="$AWS_LAMBDA_FUNCTION_TIMEOUT" -e AWS_LAMBDA_FUNCTION_NAME="$AWS_LAMBDA_FUNCTION_NAME" -e AWS_LAMBDA_FUNCTION_VERSION="$AWS_LAMBDA_FUNCTION_VERSION" -e AWS_LAMBDA_FUNCTION_INVOKED_ARN="$AWS_LAMBDA_FUNCTION_INVOKED_ARN"  --rm "lambci/lambda:java11" "com.XXX.XXX.Handler")";docker cp "/tmp/localstack/zipfile.0c90736c/." "$CONTAINER_ID:/var/task"; docker start -ai "$CONTAINER_ID";

I think this is due to the fact that the classpath arguments and java opts are only being set if the rutime is equal to LAMBDA_RUNTIME_JAVA8 (line 211 of ocalstack/localstack/services/awslambda/lambda_executors.py , commit 03c6f4bf250edd18eb818ed65090f508636b0bff)
return execute
    raise ClientError(error_response(
        'Unable to extract Java Lambda handler - file is not a valid zip/jar file', 400, error_type='ValidationError'))
def set_archive_code(code, lambda_name, zip_file_content=None):
    
    lambda_arn = func_arn(lambda_name)
    lambda_details = arn_to_lambda[lambda_arn]
    is_local_mount = code.get('S3Bucket') == BUCKET_MARKER_LOCAL
    if is_local_mount and config.LAMBDA_REMOTE_DOCKER:
        msg = 'Please note that Lambda mounts (bucket name "%s") cannot be used with LAMBDA_REMOTE_DOCKER=1'
        raise Exception(msg % BUCKET_MARKER_LOCAL)
    
    LAMBDA_EXECUTOR.cleanup(lambda_arn)
    if is_local_mount:
        
        
        
        
        return code['S3Key']
    
    zip_file_content = zip_file_content or get_zip_bytes(code)
    
    code_sha_256 = base64.standard_b64encode(hashlib.sha256(zip_file_content).digest())
    lambda_details.get_version('$LATEST')['CodeSize'] = len(zip_file_content)
    lambda_details.get_version('$LATEST')['CodeSha256'] = code_sha_256.decode('utf-8')
    tmp_dir = '%s/zipfile.%s' % (config.TMP_FOLDER, short_uid())
    mkdir(tmp_dir)
    tmp_file = '%s/%s' % (tmp_dir, LAMBDA_ZIP_FILE_NAME)
    save_file(tmp_file, zip_file_content)
    TMP_FILES.append(tmp_dir)