gzserver Does not Find Some Gazebo Plugins

[Amronos]

Environment

• OS Version: Ubuntu 24.04
• Source or binary build?
  Source - ad225a2

Description

• Expected behavior: When launching gazebo through the gz_server.launch.py launch file, I expected gazebo to find the gz_ros2_control-system plugin and not report an error.
• Actual behavior: Gazebo does not find the plugin and outputs Failed to load system plugin [gz_ros2_control-system] : Could not find shared library.

More information can be found in ros-controls/gz_ros2_control#390

Steps to reproduce

Use the following launch file (A slightly modified version of diff_drive_example.launch.py that uses gz_server.launch.py):

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument, IncludeLaunchDescription
from launch.actions import RegisterEventHandler
from launch.event_handlers import OnProcessExit
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import Command, FindExecutable, LaunchConfiguration, PathJoinSubstitution

from launch_ros.actions import Node
from launch_ros.substitutions import FindPackageShare


def generate_launch_description():
    # Launch Arguments
    use_sim_time = LaunchConfiguration('use_sim_time', default=True)

    # Get URDF via xacro
    robot_description_content = Command(
        [
            PathJoinSubstitution([FindExecutable(name='xacro')]),
            ' ',
            PathJoinSubstitution(
                [FindPackageShare('gz_ros2_control_demos'),
                 'urdf', 'test_diff_drive.xacro.urdf']
            ),
        ]
    )
    robot_description = {'robot_description': robot_description_content}
    robot_controllers = PathJoinSubstitution(
        [
            FindPackageShare('gz_ros2_control_demos'),
            'config',
            'diff_drive_controller_velocity.yaml',
        ]
    )

    node_robot_state_publisher = Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        output='screen',
        parameters=[robot_description]
    )

    gz_spawn_entity = Node(
        package='ros_gz_sim',
        executable='create',
        output='screen',
        arguments=['-topic', 'robot_description', '-name',
                   'diff_drive', '-allow_renaming', 'true'],
    )

    joint_state_broadcaster_spawner = Node(
        package='controller_manager',
        executable='spawner',
        arguments=['joint_state_broadcaster'],
    )
    diff_drive_base_controller_spawner = Node(
        package='controller_manager',
        executable='spawner',
        arguments=[
            'diff_drive_base_controller',
            '--param-file',
            robot_controllers,
            ],
    )

    return LaunchDescription([
        # Launch gazebo environment
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(
                [PathJoinSubstitution([FindPackageShare('ros_gz_sim'),
                                   'launch',
                                   'gz_server.launch.py'])]),
            launch_arguments=[('world_sdf_file', 'empty.sdf'),]),
        RegisterEventHandler(
            event_handler=OnProcessExit(
                target_action=gz_spawn_entity,
                on_exit=[joint_state_broadcaster_spawner],
            )
        ),
        RegisterEventHandler(
            event_handler=OnProcessExit(
                target_action=joint_state_broadcaster_spawner,
                on_exit=[diff_drive_base_controller_spawner],
            )
        ),
        node_robot_state_publisher,
        gz_spawn_entity,
        # Launch Arguments
        DeclareLaunchArgument(
            'use_sim_time',
            default_value=use_sim_time,
            description='If true, use simulated clock'),
    ])

[Amronos]

I tested this with a binary installation of v1.0.7 (jazzy) from the testing repository. The result is the same: using gz_sim.launch.py, the plugin is found successfully while when using gz_server.launch.py, the plugin is not found.

[Tacha-S]

I encountered the same issue. Assuming it was an environment variable problem, I added the following, and it seems the loading is working correctly.

ros_gz/ros_gz_sim/launch/gz_sim.launch.py.in

Lines 43 to 96 in 5c1251a

	class GazeboRosPaths:
	@staticmethod
	def get_paths():
	gazebo_model_path = []
	gazebo_plugin_path = []
	gazebo_media_path = []
	for package_name in get_package_names():
	package_share_path = get_package_share_directory(package_name)
	package_file_path = os.path.join(package_share_path, PACKAGE_MANIFEST_FILENAME)
	if os.path.isfile(package_file_path):
	try:
	package = parse_package(package_file_path)
	except InvalidPackage:
	continue
	for export in package.exports:
	if export.tagname == 'gazebo_ros':
	if 'gazebo_model_path' in export.attributes:
	xml_path = export.attributes['gazebo_model_path']
	xml_path = xml_path.replace('${prefix}', package_share_path)
	gazebo_model_path.append(xml_path)
	if 'plugin_path' in export.attributes:
	xml_path = export.attributes['plugin_path']
	xml_path = xml_path.replace('${prefix}', package_share_path)
	gazebo_plugin_path.append(xml_path)
	if 'gazebo_media_path' in export.attributes:
	xml_path = export.attributes['gazebo_media_path']
	xml_path = xml_path.replace('${prefix}', package_share_path)
	gazebo_media_path.append(xml_path)
	gazebo_model_path = os.pathsep.join(gazebo_model_path + gazebo_media_path)
	gazebo_plugin_path = os.pathsep.join(gazebo_plugin_path)
	return gazebo_model_path, gazebo_plugin_path
	def launch_gz(context, *args, **kwargs):
	model_paths, plugin_paths = GazeboRosPaths.get_paths()
	env = {
	"GZ_SIM_SYSTEM_PLUGIN_PATH": os.pathsep.join(
	[
	environ.get("GZ_SIM_SYSTEM_PLUGIN_PATH", default=""),
	environ.get("LD_LIBRARY_PATH", default=""),
	plugin_paths,
	]
	),
	"GZ_SIM_RESOURCE_PATH": os.pathsep.join(
	[
	environ.get("GZ_SIM_RESOURCE_PATH", default=""),
	model_paths,
	]
	),
	}

However, there is still another problem.
When executed as a component, the controller manager is also started in the same container, causing the controller manager's name to be identical to the container name. This leads to the following issues:

• The namespace specified in files like ros2_control.xacro is ignored.
• Services like controller_manager/list_controllers are prefixed with container_name/***.

[Amronos]

I encountered the same issue. Assuming it was an environment variable problem, I added the following, and it seems the loading is working correctly.

@Tacha-S could you make a PR with those changes?