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)
func_details = arn_to_lambda.get(arn)
    if not func_details:
        return not_found_error(arn)
    result = {'Tags': func_details.tags}
    return jsonify(result)
@app.route('/<version>/tags/<arn>', methods=['POST'])
def tag_resource(version, arn):
    data = json.loads(request.data)
    tags = data.get('Tags', {})
    if tags:
        func_details = arn_to_lambda.get(arn)
        if not func_details:
            return not_found_error(arn)
        if func_details:
            func_details.tags.update(tags)
    return jsonify({})
@app.route('/<version>/tags/<arn>', methods=['DELETE'])
def untag_resource(version, arn):
    tag_keys = request.args.getlist('tagKeys')
    func_details = arn_to_lambda.get(arn)
    if not func_details:
        return not_found_error(arn)
    for tag_key in tag_keys:
        func_details.tags.pop(tag_key, None)
    return jsonify({})
def serve(port, quiet=True):
    
    LAMBDA_EXECUTOR.startup()
    generic_proxy.serve_flask_app(app=app, port=port, quiet=quiet)