Append ros namespace to target container if available.

[mbharatheesha]

This PR introduces a change to fix #428.

With this change, when a composable node is loaded into a target container that is running under a ros_namespace set using <push_ros_namespace>, the target container name gets prefixed with ros_namespace using the LaunchContext. This enables the composable nodes to load into a namespaced target container.

How did I test this:

• apt install ros-rolling-image-tools
• Create a python launch file

from launch import LaunchDescription
from launch_ros.actions import LoadComposableNodes, Node, PushROSNamespace
from launch_ros.descriptions import ComposableNode

def generate_launch_description():

    set_ns = PushROSNamespace("test_ns")
    container = Node(
        name='image_container',
        package='rclcpp_components',
        executable='component_container',
        output='both',
    )

    load_composable_nodes = LoadComposableNodes(
        target_container='image_container',
        composable_node_descriptions=[
            ComposableNode(
                package='image_tools',
                plugin='image_tools::Cam2Image',
                name='cam2image',
                remappings=[('/image', '/burgerimage')],
                parameters=[{'width': 320, 'height': 240, 'burger_mode': True, 'history': 'keep_last'}],
                extra_arguments=[{'use_intra_process_comms': True}],
            ),
            ComposableNode(
                package='image_tools',
                plugin='image_tools::ShowImage',
                name='showimage',
                remappings=[('/image', '/burgerimage')],
                parameters=[{'history': 'keep_last'}],
                extra_arguments=[{'use_intra_process_comms': True}]
            ),
        ],
    )

    return LaunchDescription([set_ns, container, load_composable_nodes])

• Confirm that the composable nodes are loaded into the namespaced target container:

[INFO] [launch_ros.actions.load_composable_nodes]: Loaded node '/test_ns/cam2image' in container '/test_ns/image_container'
[component_container-1] [INFO] [1734128809.737064712] [test_ns.image_container]: Found class: rclcpp_components::NodeFactoryTemplate<image_tools::Cam2Image>
[component_container-1] [INFO] [1734128809.737089661] [test_ns.image_container]: Found class: rclcpp_components::NodeFactoryTemplate<image_tools::ShowImage>
[component_container-1] [INFO] [1734128809.737094571] [test_ns.image_container]: Instantiate class: rclcpp_components::NodeFactoryTemplate<image_tools::ShowImage>
[component_container-1] [INFO] [1734128809.742501542] [test_ns.showimage]: Subscribing to topic 'image'
[INFO] [launch_ros.actions.load_composable_nodes]: Loaded node '/test_ns/showimage' in container '/test_ns/image_container'
[component_container-1] [INFO] [1734128809.768871705] [test_ns.cam2image]: Publishing image #1
[component_container-1] [INFO] [1734128809.769063393] [test_ns.showimage]: Received image #camera_frame

• Create an xml launch file

<launch>
    <group>
        <push_ros_namespace namespace="test_ns"/>

        <node_container pkg="rclcpp_components" exec="component_container" name="container" namespace=""/>
            <load_composable_node target="container">
                <composable_node name="cam2image" pkg="image_tools" plugin="image_tools::Cam2Image">
                    <remap from="image" to="burger_image" />
                    <param name="width" value="320" />
                    <param name="height" value="240" />
                    <param name="burger_mode" value="True" />
                    <param name="history" value="keep_last" />
                </composable_node>
                <composable_node name="showimage" pkg="image_tools" plugin="image_tools::ShowImage">
                    <remap from="image" to="burger_image" />
                    <param name="history" value="keep_last" />
                </composable_node>
            </load_composable_node>
    </group>
</launch>

• Confirm that the composable nodes are loaded into the namespaced target container:

[INFO] [launch_ros.actions.load_composable_nodes]: Loaded node '/test_ns/cam2image' in container '/test_ns/container'
[component_container-1] [INFO] [1734130914.070237617] [test_ns.container]: Found class: rclcpp_components::NodeFactoryTemplate<image_tools::Cam2Image>
[component_container-1] [INFO] [1734130914.070265706] [test_ns.container]: Found class: rclcpp_components::NodeFactoryTemplate<image_tools::ShowImage>
[component_container-1] [INFO] [1734130914.070270385] [test_ns.container]: Instantiate class: rclcpp_components::NodeFactoryTemplate<image_tools::ShowImage>
[component_container-1] [INFO] [1734130914.073884311] [test_ns.showimage]: Subscribing to topic 'image'
[INFO] [launch_ros.actions.load_composable_nodes]: Loaded node '/test_ns/showimage' in container '/test_ns/container'
[component_container-1] [INFO] [1734130914.101434113] [test_ns.cam2image]: Publishing image #1
[component_container-1] [INFO] [1734130914.102238122] [test_ns.showimage]: Received image #camera_frame

• ros2 node list

/launch_ros_780940
/test_ns/cam2image
/test_ns/container
/test_ns/showimage

Without the changes in this PR, the output from the launch would be:

[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [component_container-1]: process started with pid [779037]

And the composable nodes wouldn't show up with ros2 node list

/launch_ros_779454
/test_ns/container

[mbharatheesha]

@ahcorde @sloretz A friendly ping on this.

[fujitatomoya]

i think this is correct fix, i will start the CI.

CC: @sloretz @ahcorde

[fujitatomoya]

Pulls: #429
Gist: https://gist.githubusercontent.com/fujitatomoya/c181a9c225d235c70f1dc8fc33c7e8c5/raw/c90c650b79c5dd5c861551173a24442c69d68d04/ros2.repos
BUILD args: --packages-above-and-dependencies launch_ros
TEST args: --packages-above launch_ros
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/15028

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[mbharatheesha]

Thanks @fujitatomoya . All builds succeeded it seems ☺️

[fujitatomoya]

@ahcorde @sloretz can we have a review for this?

[sloretz]

Thank you for the PR!

I'm not too familiar with the launch internals. Would you be willing to add a test to https://github.com/ros2/launch_ros/tree/rolling/launch_ros/test that shows how this fixes the issue? 🧇

[MartinCornelis2]

@mbharatheesha I'm wondering if containers should automatically get the ros namespace pushed onto them. What if you have a higher level abstract container in which you want to put a bunch of namespaced nodes and topics. This would make a setup like this much harder to achieve, because you would have to namespace everything going into the container separately.

Example:
container use-case 1:
{lidar container} : [lidar1 driver] [lidar1 processing] [lidar2 driver][lidar2 processing]

container use-case 2:
{lidar1 container}: [lidar1 driver] [lidar1 processing]
{lidar2 container}: [lidar2 driver][lidar2 processing]

This change will make it such that you can no longer push ros namespace in use-case 1, but it makes use-case 2 easier to achieve.

So the only question for me is, how often do people use use-case 1 vs use-case 2, if use-case 1 never happens then this is an improvement, otherwise it makes use-case 1 cumbersome.