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)
if not msg:
        msg = 'The resource you requested does not exist.'
        if ref:
            msg = '%s not found: %s' % ('Function' if ':function:' in ref else 'Resource', ref)
    return error_response(msg, 404, error_type='ResourceNotFoundException')
@app.before_request
def before_request():
    
    transfer_encoding = request.headers.get('Transfer-Encoding', '').lower()
    if transfer_encoding == 'chunked':
        request.environ['wsgi.input_terminated'] = True
@app.route('%s/functions' % PATH_ROOT, methods=['POST'])
def create_function():
    """ Create new function
        ---
        operationId: 'createFunction'
        parameters:
            - name: 'request'
              in: body
    """
    arn = 'n/a'
    try:
        data = json.loads(to_str(request.data))
        lambda_name = data['FunctionName']
        event_publisher.fire_event(event_publisher.EVENT_LAMBDA_CREATE_FUNC,
            payload={'n': event_publisher.get_hash(lambda_name)})