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)
docker_cmd = self._docker_cmd()
            status = self.get_docker_container_status(func_arn)
            LOG.debug('Priming docker container (status "%s"): %s' % (status, container_name))
            docker_image = Util.docker_image_for_runtime(runtime)
            rm_flag = Util.get_docker_remove_flag()
            
            if status < 1:
                
                self.destroy_docker_container(func_arn)
                env_vars_str = ' '.join(['-e {}={}'.format(k, cmd_quote(v)) for (k, v) in env_vars])
                network = config.LAMBDA_DOCKER_NETWORK
                network_str = '--network="%s"' % network if network else ''
                mount_volume = not config.LAMBDA_REMOTE_DOCKER
                lambda_cwd_on_host = Util.get_host_path_for_path_in_docker(lambda_cwd)
                mount_volume_str = '-v "%s":/var/task' % lambda_cwd_on_host if mount_volume else ''
                
                LOG.debug('Creating container: %s' % container_name)
                cmd = (
                    '%s create'
                    ' %s'  
                    ' --name "%s"'
                    ' --entrypoint /bin/bash'  
                    ' %s'
                    ' --interactive'  
                    ' -e AWS_LAMBDA_EVENT_BODY="$AWS_LAMBDA_EVENT_BODY"'
                    ' -e HOSTNAME="$HOSTNAME"'
                    ' -e LOCALSTACK_HOSTNAME="$LOCALSTACK_HOSTNAME"'
                    '  %s'  
                    '  %s'  
                    ' %s'