Nodelet topic remapping not working inside namespace

asked 2020-06-23 08:41:44 -0600

Bhazza gravatar image

I have a launch script that launches multiple instances of the same nodelet, which share the same nodelet manager (to allow zero-copy messaging). When I run launch file I get the following error, presumably as a consequence of each nodelet using the same parameter names in the same namespace:

Tried to advertise a service that is already advertised in this node

I think the solution to this is to place the nodelets in different namespaces, however I am struggling to get it to work. Hopefully the following toy example - using point_cloud_xyz for simplicity (I'm using a custom nodelet in my actual launch file) - outlines the problem I'm facing.

This code runs fine:

<launch>
    <arg name="nodelet_manager_name"            default="camera_nodelet_manager" />

    <node pkg="nodelet" type="nodelet" name="$(arg nodelet_manager_name)" args="manager"/>

    <node pkg="nodelet" type="nodelet" name="point_cloud_xyz"
        args="load depth_image_proc/point_cloud_xyz $(arg nodelet_manager_name) --no-bond"
        respawn="true>
            <remap from="camera_info"           to="/depth/camera_info" />
            <remap from="image_rect"            to="/depth/image_rect"   />
            <remap from="points"                to="/depth/points"    />
    </node>
</launch>

And if I run it with the "--screen" flag I see that the topics are remapped as expected:

[ INFO] [1592917605.947825944]: Loading nodelet /point_cloud_xyz of type depth_image_proc/point_cloud_xyz to manager camera_nodelet_manager with the following remappings:

[ INFO] [1592917605.948422793]: /camera_info -> /depth/camera_info

[ INFO] [1592917605.948437110]: /image_rect -> /depth/image_rect

[ INFO] [1592917605.948446947]: /points -> /depth/points

And the nodelet successfully runs and publishes points to the topic.

However if I try to put the nodelet into a namespace (called "camera"):

<launch>
    <arg name="nodelet_manager_name"            default="camera_nodelet_manager" />

    <node pkg="nodelet" type="nodelet" name="$(arg nodelet_manager_name)" args="manager"/>

    <group ns="camera">
        <node pkg="nodelet" type="nodelet" name="point_cloud_xyz"
            args="load depth_image_proc/point_cloud_xyz $(arg nodelet_manager_name) --no-bond"
            respawn="true">
                <remap from="camera_info"           to="/depth/camera_info" />
                <remap from="image_rect"            to="/depth/image_rect"   />
                <remap from="points"                to="/depth/points"    />
        </node>
    </group>
</launch>

The remapping looks like I would expect, with the topics for the nodelet now within the "camera" namespace, but the target remappings remaining the same (since I have defined them as global with the preceeding "/"):

[ INFO] [1592917948.909617098]: Loading nodelet /camera/point_cloud_xyz of type depth_image_proc/point_cloud_xyz to manager camera_nodelet_manager with the following remappings:

[ INFO] [1592917948.910396273]: /camera/camera_info -> /depth/camera_info

[ INFO] [1592917948.910409509]: /camera/image_rect -> /depth/image_rect

[ INFO] [1592917948.910415959]: /camera/points -> /depth/points

But this doesn't work because now there are no points published to any topic.

Of course, it will work if I move the nodelet manager into the "camera" namespace too, but as I note at the start, I need to run multiple instances of the same nodelet under a single nodelet manager without the parameters colliding with each other.

I have been through a multitude of other answers on here, and feel like I've tried all manner of alternatives, all with no success. So I can only assume I am fundamentally misunderstanding something. Any help would be gratefully received!

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Comments

Any update?

achmad_fathoni gravatar image achmad_fathoni  ( 2021-04-29 10:06:47 -0600 )edit