API to programmatically modify ROS2 Context domain_id in USD files

[dongzhue]

Hi, I have a workflow where each USD scene contains:

1. ROS Clock node (On Playback Tick) — to execute other graph nodes every simulation frame.
2. ROS2 Context node — to create a context using either the given Domain ID or the ROS_DOMAIN_ID environment variable.
3. ROS2 Subscriber node — to subscribe to a ROS 2 topic of any message type.

Currently, all USDs share the same ROS Clock domain_id（default 0）, which causes topic conflicts when running multiple simulations in parallel.

Feature request
I would like to automatically edit the domain_id attribute inside the USD’s ROS Clock node so that each USD file has a unique domain ID for ROS2 communication.

The goal is:

1. Each simulation instance uses a different domain_id.
2. ROS2 topics from different simulations don’t conflict.
3. This should be done programmatically (e.g., via Python API or Omniverse Kit script), not manually in the Omniverse GUI.

Questions:

1. Is there an existing Omniverse API or Python scripting method to modify the ROS Clock’s domain_id inside a USD file?
2. Can we set this property dynamically when loading the USD, instead of editing and saving it manually?

[dongzhue]

In my original request, I mentioned modifying the domain_id of the ROS Clock node.

However, my actual requirement is broader: I need to update the domain_id in all relevant ROS nodes inside the USD, especially the ROS2 Context node, because this node is responsible for creating the ROS 2 context and determines the domain in which all other ROS nodes operate.

Here is the reference from the ROS2 Context node documentation:

ROS2 Context
This node creates a ROS2 Context for a given domain ID.

Installation:
To use this node enable isaacsim.ros2.bridge in the Extension Manager.

Inputs:

• Domain Id (inputs:domain_id) [uchar]
  Domain ID for ROS context. Default: 0
• Use Domain ID Env Var (inputs:useDomainIDEnvVar) [bool]
  Set to true to use ROS_DOMAIN_ID environment variable if set. Defaults to domain_id if not found. Default: True

Outputs:

• Context (outputs:context) [uint64]
  Handle to initialized ROS2 context

Metadata:

• Unique ID: isaacsim.ros2.bridge.ROS2Context
• Version: 2
• Extension: isaacsim.ros2.bridge
• Implementation Language: C++
  Updated request:

I would like to have an API or scripting method to programmatically set the domain_id for all ROS2 Context nodes within a USD scene before simulation starts, so that each USD can have a unique ROS domain without manually editing them in the GUI.

This would make it possible to run multiple simulations in parallel (e.g., 24 robots with domain IDs 1–24) without ROS 2 topic conflicts.

[dongzhue]

I noticed that the underlying implementation isaacsim::ros2::bridge::Ros2ContextHandleImpl provides an init() method with parameters setDomainId and domainId, which would technically allow setting a unique domain ID programmatically.
However, I would like to know if there is an official Omniverse Kit or Python API that exposes this functionality for all ROS2 Context nodes in a USD scene, so I can set their domain IDs dynamically at load time without modifying the C++ extension.

[vick-yu]

There are several ways to programmatically modify the domain_id attribute of ROS2 Context nodes in USD files. For the most accurate implementation, I recommend referencing the exts/isaacsim.ros2.bridge/isaacsim/ros2/bridge/ogn/tests/usd/OgnROS2ContextTemplate.usda file, which provides the canonical structure of ROS2 Context nodes.

[dongzhue]

Hi, I would like to confirm if my understanding is correct:

If inputs:useDomainIDEnvVar is set to true, I can launch multiple Isaac Sim instances with different ROS 2 domains by setting the ROS_DOMAIN_ID environment variable before each launch, for example:
ROS_DOMAIN_ID=1 ./isaac-sim.sh （load sceneA.usd） ROS_DOMAIN_ID=2 ./isaac-sim.sh （load sceneB.usd）
This should ensure that each simulation runs in a separate ROS 2 domain without topic conflicts. Could you confirm if this approach is supported?

[vick-yu]

Based on the official Isaac Sim documentation and current understanding, your approach is correct and should be supported.

Note: I haven’t directly verified this workflow yet, but it matches the documented API behavior. If you encounter any issues when deploying, please share details here—happy to help troubleshoot!

[dongzhue]

def modify_existing_ros2_context(set_ros_domain_id):
    try:
        possible_paths = [
            "/World/ROS_Clock/ros2_context",
            "/World/Nova_Carter_ROS/front_hawk/ros2_context",
            "/World/Nova_Carter_ROS/transform_tree_odometry/ros2_context",
            "/World/Nova_Carter_ROS/differential_drive/ros2_context",
            "/World/Nova_Carter_ROS/chassis_imu/ros2_context",]
        for path in possible_paths:
            ros2_prim = stage.GetPrimAtPath(path)
            if ros2_prim and ros2_prim.IsValid():
                domain_attr = ros2_prim.GetAttribute("inputs:domain_id")
                if domain_attr:
                    domain_attr.Set(set_ros_domain_id)
                for attr_name in ["inputs:domain_id", "domain_id", "inputs:domainID"]:
                    try:
                        attr = ros2_prim.GetAttribute(attr_name)
                        if attr:
                            attr.Set(set_ros_domain_id)
                    except:
                        continue
            else:      
    except Exception as e:
        return False
modify_existing_ros2_context(ros_domain_id)

Thanks for your reply, I solved my problem by this code