Add Graph description messages to rosgraph_msgs by emersonknapp · Pull Request #188 · ros2/rcl_interfaces

emersonknapp · 2026-03-18T19:38:58Z

Description

Fixes #182

Add new message definitions to rosgraph_msgs that can be used to describe a running or potential ROS Graph.

Graph: a list of nodes
Node : describe a single node's parameters and interface endpoints
Topic: describe a single topic endpoint, either Publisher or Subscription
Service: describe a single service endpoint, either Server or Client
Action: describe a single action endpoint, either Server or Client
QoSProfile: describe a QoS Profile, either offered or requested
InterfaceType: identify a rosidl type
TypeHash: identify a REP-2016 RIHS type hash (rosidl_runtime_c defined type)

This is intended to supplant the definitions in use at https://github.com/ros-tooling/graph-monitor/tree/main/rosgraph_monitor_msgs

Is this user-facing behavior change?

Yes

Did you use Generative AI?

No

Additional Information

Part of the NoDL and rosgraph_monitor work being done within the ROSGraph Working Group.

We would like to get these messages into the core for Lyrical, so that we can build tools around them for release into that LTS distro.

These messages act as a counterpart to the NoDL schema, being used to output either a desired or observed state of a ROS application as a message between nodes. The NoDL schema is not a strict duplicate of the information that these messages will contain, because:

NoDL will contain information relevant to code generation that is of more detail than can be observed by graph inspection
These messages contain fields about "instantiated values" that do not exist at specification time, such as actual parameter values.
The contents of these messages generally refer to resolved fully-qualified graph names after namespacing and remapping are applied, something that is not known or relevant at the node specification level.

Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com>

wjwwood

Looks reasonable to me

skyegalaxy

seems like pretty much exactly what was discussed at this week's ROSgraph WG

rosgraph_msgs/msg/QoSProfile.msg

rosgraph_msgs/msg/Service.msg

rosgraph_msgs/msg/Action.msg

skyegalaxy

need to add DCO for the last commit

Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com>

emersonknapp · 2026-03-23T19:16:01Z

Note for reviewers - I'm updating the docstrings with more information, and calling out the change here.

I was trying to use these messages to represent both the "abstract descriptor" of these entities, as well as the "observed/observable instantiation" of them. However, those two concepts have some key disjunctions.

Therefore, I am focusing in on the latter - observed/observable instantiation. We will use NoDL for the "abstract descriptor" and may or may not choose to be able to represent it as messages, which will be a separate exercise.

Thanks @fujitatomoya for taking the close look that forced this decision

…ns specifically to observed/actual state, rather than trying to fold in an abstract descriptor meaning Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com>

rosgraph_msgs/msg/TypeHash.msg

skyegalaxy · 2026-03-23T19:53:02Z

rosgraph_msgs/msg/Node.msg

+Service[] service_servers
+
+Action[] action_clients
+Action[] action_servers


Would these lists allow for duplicates, say for example if a node spins up multiple (action) clients to the same (action) server for whatever reason?

nothing prevents it. based on the current representation you wouldn't be able to tell them apart though.

I'm now wondering if I need to basically have the leaf message actually be an encoding of rmw_topic_endpoint_info (and service_endpoint_info), and include the GID as well.

That would directly represent the "observable state" as it's defined most fundamentally in the API, if we try to match those definitions.

rosgraph_msgs/msg/TypeHash.msg

christophebedard · 2026-04-02T22:12:54Z

@emersonknapp is this ready to merge? I can run CI

christophebedard · 2026-04-02T22:13:49Z

Pulls: #188
Gist: https://gist.githubusercontent.com/christophebedard/854094017ffcb7dbc8374893da5aeb99/raw/7a802edfc8d7a6d4ce2b7610570e86bd9e86bf9e/ros2.repos
BUILD args: --packages-above-and-dependencies rosgraph_msgs
TEST args: --packages-above rosgraph_msgs
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18808

Linux
Linux-aarch64
Linux-rhel
Windows

skyegalaxy · 2026-04-06T18:37:35Z

Linux-rhel
Windows

emersonknapp · 2026-04-08T17:09:50Z

CI failures unrelated, merging

emersonknapp · 2026-04-10T17:10:31Z

@Mergifyio backport humble jazzy kilted

mergify · 2026-04-10T17:10:45Z

backport humble jazzy kilted

✅ Backports have been created

Details

#189 Add Graph description messages to rosgraph_msgs (backport #188) has been created for branch humble
#190 Add Graph description messages to rosgraph_msgs (backport #188) has been created for branch jazzy
#191 Add Graph description messages to rosgraph_msgs (backport #188) has been created for branch kilted

Add new message definitions to rosgraph_msgs that can be used to describe a running or potential ROS Graph. Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com> (cherry picked from commit 2209d02)

Add new message definitions to rosgraph_msgs that can be used to describe a running or potential ROS Graph. (cherry picked from commit 2209d02) Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com> Co-authored-by: Emerson Knapp <537409+emersonknapp@users.noreply.github.com>

Add first pass of Graph description messages to rosgraph_msgs

7fea0f1

Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com>

emersonknapp force-pushed the emerson/graph-messages branch from dc66d05 to 7fea0f1 Compare March 18, 2026 19:40

emersonknapp mentioned this pull request Mar 19, 2026

Create new NoDL v2 schema within a new package named nodl ros-tooling/nodl#50

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wjwwood approved these changes Mar 20, 2026

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emersonknapp mentioned this pull request Mar 20, 2026

Design document for Node Interface Definition Language (IDL) ros2/design#266

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skyegalaxy approved these changes Mar 20, 2026

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emersonknapp mentioned this pull request Mar 20, 2026

Use upstream rosgraph_msgs ros-tooling/graph-monitor#49

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fujitatomoya reviewed Mar 23, 2026

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skyegalaxy requested changes Mar 23, 2026

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Add BEST_AVAILABLE QoS values

0892e87

Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com>

emersonknapp force-pushed the emerson/graph-messages branch from 31aa0e1 to 0892e87 Compare March 23, 2026 18:34

Update Services and Actions to have QoS info, reframe these definitio…

c293699

…ns specifically to observed/actual state, rather than trying to fold in an abstract descriptor meaning Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com>

emersonknapp requested review from fujitatomoya, skyegalaxy and wjwwood March 23, 2026 19:42

emersonknapp commented Mar 23, 2026

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rosgraph_msgs/msg/TypeHash.msg Show resolved Hide resolved

skyegalaxy approved these changes Mar 23, 2026

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fujitatomoya approved these changes Mar 24, 2026

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christophebedard assigned emersonknapp Apr 2, 2026

kamal2730 mentioned this pull request Apr 8, 2026

Represent Services in rosgraph_monitor_msgs ros-tooling/graph-monitor#45

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emersonknapp merged commit 2209d02 into rolling Apr 8, 2026
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mergify bot mentioned this pull request Apr 10, 2026

Add Graph description messages to rosgraph_msgs (backport #188 humble) #189

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mergify bot mentioned this pull request Apr 10, 2026

Add Graph description messages to rosgraph_msgs (backport #188 jazzy) #190

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mergify bot mentioned this pull request Apr 10, 2026

Add Graph description messages to rosgraph_msgs (backport #188 kilted) #191

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