[ROS2 Humble] Error while using IPC in composition

[Myzhar]

When I try to enable IPC in composition I get this error:
Component constructor threw an exception: intraprocess communication is not allowed with a zero qos history depth value

The default QoS settings for the depthimage_to_laserscan component are not good for using IPC.

Example:

# ZED Wrapper component
    zed_wrapper_component = ComposableNode(
        package='zed_components',
        namespace=camera_name_val,
        plugin='stereolabs::ZedCamera',
        name=zed_node_name,
        parameters=[
            # YAML files
            config_common_path,  # Common parameters
            config_camera_path,  # Camera related parameters
            # Overriding
            {
                'general.camera_name': camera_name_val,
                'general.camera_model': camera_model_val,
                'general.svo_file': svo_path,
                'general.serial_number': serial_number
            }
        ],
        extra_arguments=[{'use_intra_process_comms': True}]
    )

    # Depth to Laser scan component
    zed_cvt_component = ComposableNode(
        package='depthimage_to_laserscan',
        namespace=camera_name_val,
        plugin='depthimage_to_laserscan::DepthImageToLaserScanROS',
        name='depthimage_to_laserscan',
        parameters=[
            config_path_cvt,
            # Overriding
            {
                'output_frame': camera_depth_frame,
                'qos_overrides./parameter_events.publisher.depth': 5
            }],
        remappings=[
                ('depth', zed_node_name_val + '/depth/depth_registered'),
                ('depth_camera_info', zed_node_name_val + '/depth/camera_info')
            ],
        extra_arguments=[{'use_intra_process_comms': True}]
    )

    # ROS 2 Component Container
    container = ComposableNodeContainer(
            name='zed_depth_to_laserscan',
            namespace=camera_name_val,
            package='rclcpp_components',
            executable='component_container',
            composable_node_descriptions=[
                zed_wrapper_component,
                zed_cvt_component
            ],
            output='screen',
    )

[Myzhar]

Read mode on Stack Exchange.

[clalancette]

Based on some internal discussion as well as the Stack Exchange thread, I think the solution here is to switch away from SystemDefaultsQoS here in depthimage_to_laserscan, and to enable qos_overrides. We still have a bug down in rclcpp where intraprocess comms should not throw this error, but depthimage_to_laserscan should also not be using SystemDefaultsQoS.

@Myzhar If you'd like to open a PR to do that, I'd be happy to review it.

[Myzhar]

@clalancette I will try to work on this during the weekend. 👍

[clalancette]

@clalancette I will try to work on this during the weekend. 👍

Fantastic, thank you!

[Myzhar]

@clalancette I tested the fix with my launch file and I confirm that now I can enable the IPC option also for the depthimage_to_laserscan node component by uncommenting the launch file line
#extra_arguments=[{'use_intra_process_comms': True}] # Uncomment when supported by the package

I am not sure if there is a way to effectively test whether IPC is enabled and being used correctly.

[clalancette]

I am not sure if there is a way to effectively test whether IPC is enabled and being used correctly.

Yeah, we should be able to add launch tests to the tests. I'll comment on the PR.

[Myzhar]

Is there a command to get the status of IPC while a node is running? I'd like to add it to diagnostic.

[clalancette]

Is there a command to get the status of IPC while a node is running? I'd like to add it to diagnostic.

I'm not sure, to be honest.