Question

Hi, I am experiencing a weird behavior of the ros2 launch command.

Using following example launch file from the robot_localization packge:

from launch import LaunchDescription
from ament_index_python.packages import get_package_share_directory
import launch_ros.actions
import os
import yaml
from launch.substitutions import EnvironmentVariable
import pathlib
import launch.actions
from launch.actions import DeclareLaunchArgument

def generate_launch_description():
    return LaunchDescription([
        launch_ros.actions.Node(
            package='robot_localization',
            node_executable='ekf_node',
            node_name='ekf_filter_node',
            output='screen',
            parameters=[os.path.join(get_package_share_directory("robot_localization"), 'params', 'ekf.yaml')],
           ),
])

creates following output:

$ ros2 launch robot_localization ekf.launch.py 
[INFO] [launch]: All log files can be found below /home/xxx/.ros/log/2020-02-14-12-59-00-118313-xxx-22388
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [ekf_node-1]: process started with pid [22398]
[ekf_node-1] [WARN] [rcl.logging_rosout]: Publisher already registered for provided node name. If this is due to multiple nodes with the same name then all logs for that logger name will go out over the existing publisher. As soon as any node with that name is destructed it will unregister the publisher, preventing any further logs for that name from being published on the rosout topic.
[ekf_node-1] X acceleration is being measured from IMU; X velocity control input is disabled

Listing running nodes with ros2 node list also shows me two ekf_nodes.

The same happens with ros2 cartographer_ros node.

Any Idea why this is happening? I am able to launch other nodes without any problem.

Asked by potentialdiffer on 2020-02-14 07:11:18 UTC

Answer 1

Removing the line that names the node fixed it for me, ie. this line:

node_name='ekf_filter_node',

Asked by ddengster on 2020-04-30 01:54:06 UTC

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Thanks! It also fixes it for me.

Asked by DanielRobotics on 2020-04-30 02:41:00 UTC

Though it fixed the problem with the two nodes it seems to cause another error for me. When I remove the naming lines I get a datum error and I receive no information on my /odometry/filtered and /odometry/gps. If I move the naming lines back in I get the duplicate nodes but the datum error is not coming and data is again coming on my /odometry/filtered and /odometry/gps. @Tom Moore do you know why this is happening?

[navsat_transform_node-4] [INFO] [navsat_transform]: Datum (latitude, longitude, altitude) is (-1246152232, -1246031536, -518309968) 
[navsat_transform_node-4] [INFO] [navsat_transform]: Datum UTM coordinate is (-124615232, -1246031536)

Asked by DanielRobotics on 2020-05-06 04:45:08 UTC

Check that node naming change did not break your parameter YAML files.

Asked by hidmic on 2020-05-07 08:59:44 UTC

Any idea why adding the node name parameter causes this error?

Asked by nnmm on 2020-11-24 11:07:52 UTC

Thanks for pointing out this solution, I solved the same problem. But if I remove the node name, why doesn't the node become duplicate? We would appreciate it if you could tell us why.

Asked by HyeonJuChoi on 2022-07-05 01:42:09 UTC

Mb it's about too late, but anyway. I believe inside your "node" you have two or more nodes with different names of course. When you set name attr in launch it tells ros2 to force renaming of inside node. That way all nodes you create inside one app will be rename with the single name, that you set in launch

Asked by DrShiki on 2023-07-21 03:23:09 UTC

ros2 launch creates two nodes of same type

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