High CPU when subscribing to parameter_events with Discovery Server

[outrider-jhulas]

Is there an already existing issue for this?

• I have searched the existing issues

Expected behavior

Subscribing to the /parameter_events topic while using Discovery server shouldn't cause the CPU of the subscriber process to go 100%.

Current behavior

When subscribing to the /parameter_events topic in one node and launching a composable node container with few even very simple composable nodes (5-10), there is a significant spike of the CPU usage from around 0% to 100%.

• The nodes need to be launched with the discovery server present, to observer the CPU spike
• No significant spike when publishing from the cli
• Launching the nodes in multiple separate processes doesn't cause the issue
• If the simple node has the start_parameter_event_publisher(false) and start_parameter_services(false) options set, then there is no CPU spike

Steps to reproduce

1. Create a node with a subscriber to the /parameter_events

SimpleMonitor::SimpleMonitor(const rclcpp::NodeOptions & options)
: Node("simple_monitor", options)
  , parameter_event_subscription_(
    this->create_subscription<rcl_interfaces::msg::ParameterEvent>(
      "/parameter_events", rclcpp::QoS(1),
      [](const rcl_interfaces::msg::ParameterEvent::SharedPtr) {
        // Do nothing
      }))
{}

2. Create a simple node with a single pub or sub, of any topic.
3. Create a launch file to launch multiple nodes in a container, eg:

def generate_launch_description():
    # Launch configurations
    node_number = LaunchConfiguration('node_number')

    # Arguments
    node_number_cmd = DeclareLaunchArgument(
        'node_number',
        default_value='1',
        description='repeats.')

    def container_launch(context):
        """Launch the node."""

        nodes = []
        for i in range(int(node_number.perform(context))):
            nodes.append(ComposableNode(
                package=PACKAGE,
                plugin='simple_node::SimpleNode',
                name='simple_node_' + str(i),
            ))
        container_cmd = ComposableNodeContainer(
            name='my_node_container',
            package='rclcpp_components',
            executable='component_container',
            composable_node_descriptions=nodes,
            output='screen')

        return container_cmd

    ld = LaunchDescription()
    ld.add_action(node_number_cmd)
    ld.add_action(OpaqueFunction(function=container_launch))
    return ld

4. Launch the subscriber node and then the container.
5. Observe the CPU spike

Fast DDS version/commit

Fast DDS: ros-humble-fastrtps: 2.6.6-1jammy.20230919.195605
Discovery server: fastdds-tools: 2.5.0+ds-3

Platform/Architecture

Other. Please specify in Additional context section.

Transport layer

Default configuration, UDPv4 & SHM

Additional context

Ubuntu 22.04
ROS2 Humble
The discovery server and the ros2 application running in two separate docker containers

XML configuration file

<?xml version="1.0" encoding="UTF-8" ?>
<!-- Copyright 2023 Outrider Technologies, Inc.  CONFIDENTIAL. -->
<dds>
    <profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles">
        <participant profile_name="super_client_profile" is_default_profile="true">
            <rtps>
                <builtin>
                    <discovery_config>
                        <discoveryProtocol>SUPER_CLIENT</discoveryProtocol>
                        <discoveryServersList>
                            <RemoteServer prefix="44.53.00.5f.45.50.52.4f.53.49.4d.41">
                                <metatrafficUnicastLocatorList>
                                    <locator>
                                        <udpv4>
                                            <address>127.0.0.1</address>
                                            <port>11812</port>
                                        </udpv4>
                                    </locator>
                                </metatrafficUnicastLocatorList>
                            </RemoteServer>
                        </discoveryServersList>
                    </discovery_config>
                </builtin>
            </rtps>
        </participant>
    </profiles>
</dds>

Relevant log output

No response

Network traffic capture

No response