Sub-node name is ignored in service name resolving

[PfeifferMicha]

When I create sub-nodes using Node::create_sub_node() and then resolve a private name on this sub-node, the sub-namespace is ignored.

    auto nh_left = this->create_sub_node( "left" );
    std::string resolved_service_name = nh_left->get_node_base_interface()->resolve_topic_or_service_name( 
                                                                                                                                                   "~/set_camera_info", true, false );

Resolves to: /test_cam_info_manager/set_camera_info
But I would expect it to resolve to: /test_cam_info_manager/**left**/set_camera_info

Background:
In order to create two CameraInfoManager's for a stereo setup, I need some way to push the CameraInfoManagers into a sub-namespace. I thought this is exactly what sub-nodes are for, but it's not working. Original issue: ros-perception/image_common#341

Note: In rolling release, I believe this can be circumvented because CameraInfoManager has a new namespace parameter, but this is not the case in jazzy.

Required Info:

• Operating System:
  • Ubuntu 24.04
• Installation type:
  • binaries
• Version or commit hash:
  • jazzy
• Client library (if applicable):
  • rclcpp

[fujitatomoya]

@PfeifferMicha thanks for creating issue, this looks like bug.

one question, can you reproduce this issue with rolling build as well? self-contained example would be appreciated.

[PfeifferMicha]

Thanks for the reply!

Here's my minimal example. Please see the Readme for description of the error/expected outcome.
https://github.com/PfeifferMicha/test_cam_info_manager

I tried with the CI nightly rolling build from here:
https://ci.ros2.org/view/packaging/job/packaging_linux/lastBuild/
Revision: 022da8a9eaa83b4ae8f7b770bdd2a4c700bf1d70

The error is still there.

[wjwwood]

The reason for this is that the "sub-node" feature exists only in the rclcpp::Node class. It does not extend down into the NodeInterface classes, therefore the way that the CameraInfoManager is using a NodeInterface rather than a Node. So I don't consider it to be a bug exactly, but just a limitation of the sub-node feature.

You lose the feature when you do nh_left->get_node_base_interface(), and it's the same for both Services and Topics.

There's a few options to move forward here:

• you could have the CameraInfoManager take a Node, which I don't really recommend, because we've been pushing people to take the interfaces instead
• you could extend the sub-node feature down into the node interfaces classes, but that's tricky because you may have multiple sub nodes going at one time, but it could be done I think
• you could extract the sub namespace with Node::get_sub_namespace() or similar, and pass it to the CameraInfoManager along side the node interface

see:

rclcpp/rclcpp/include/rclcpp/node.hpp

Lines 1496 to 1554 in 48a4761

	/// Return the sub-namespace, if this is a sub-node, otherwise an empty string.
	/**
	* The returned sub-namespace is either the accumulated sub-namespaces which
	* were given to one-to-many create_sub_node() calls, or an empty string if
	* this is an original node instance, i.e. not a sub-node.
	*
	* For example, consider:
	*
	* ```cpp
	* auto node = std::make_shared<rclcpp::Node>("my_node", "my_ns");
	* node->get_sub_namespace(); // -> ""
	* auto sub_node1 = node->create_sub_node("a");
	* sub_node1->get_sub_namespace(); // -> "a"
	* auto sub_node2 = sub_node1->create_sub_node("b");
	* sub_node2->get_sub_namespace(); // -> "a/b"
	* auto sub_node3 = node->create_sub_node("foo");
	* sub_node3->get_sub_namespace(); // -> "foo"
	* node->get_sub_namespace(); // -> ""
	* ```
	*
	* get_namespace() will return the original node namespace, and will not
	* include the sub-namespace if one exists.
	* To get that you need to call the get_effective_namespace() method.
	*
	* \sa get_namespace()
	* \sa get_effective_namespace()
	* \return the sub-namespace string, not including the node's original namespace
	*/
	RCLCPP_PUBLIC
	const std::string &
	get_sub_namespace() const;
	/// Return the effective namespace that is used when creating entities.
	/**
	* The returned namespace is a concatenation of the node namespace and the
	* accumulated sub-namespaces, which is used as the namespace when creating
	* entities which have relative names.
	*
	* For example, consider:
	*
	* ```cpp
	* auto node = std::make_shared<rclcpp::Node>("my_node", "my_ns");
	* node->get_effective_namespace(); // -> "/my_ns"
	* auto sub_node1 = node->create_sub_node("a");
	* sub_node1->get_effective_namespace(); // -> "/my_ns/a"
	* auto sub_node2 = sub_node1->create_sub_node("b");
	* sub_node2->get_effective_namespace(); // -> "/my_ns/a/b"
	* auto sub_node3 = node->create_sub_node("foo");
	* sub_node3->get_effective_namespace(); // -> "/my_ns/foo"
	* node->get_effective_namespace(); // -> "/my_ns"
	* ```
	*
	* \sa get_namespace()
	* \sa get_sub_namespace()
	* \return the sub-namespace string, not including the node's original namespace
	*/
	RCLCPP_PUBLIC
	const std::string &
	get_effective_namespace() const;

[alsora]

Hi @PfeifferMicha , any update on this?

[PfeifferMicha]

Thanks a lot for the suggestions @wjwwood !
@alsora I've not worked too much with the CameraInfoManager code before, so I have a hard time judging what's the best approach here. I asked people to chime in on the original issue (ros-perception/image_common#341), will wait and see if there's a response.

[fabianhirmann]

I wasn't sure if I should create a new issue but I noticed that similar to that also relative topic/service names are ignoring the sub node name.

For example:

auto node = rclcpp::Node::make_shared("example_node");
auto node_pub_relative = node->create_publisher<std_msgs::msg::String>("~/node_pub_relative", 10);
// This creates "/example_node/node_pub_relative"

auto sub_node = node->create_sub_node("subnode");
auto sub_node_pub_relative = sub_node->create_publisher<std_msgs::msg::String>("~/sub_node_pub_relative", 10);
// This creates "/example_node/sub_node_pub_relative" while I was expecting "/example_node/subnode/sub_node_pub_relative"