Generate mermaid description of ROS2 graphs to add on your markdown files.
In order to have better architecture documentation, graphs of nodes and topics are needed. Nonetheless, nobody wants to maintain these graphs and even do it from scratch. Because of that, a tool that does it automatedly is required. The first alternative is rqt-graph but it does not include services/actions information and adds some non-required information when we filter by a node. Normally the workflow includes connecting to a terminal where the ros system is running, launching the rqt-graph, saving the resulting image, and uploading it to the cloud to include it in the documentation.
To make our life easier and to generate graphs that include all the information that we want this tool was created
You need to have already installed ROS2 (tested on humble distro).
pip install ros2-graph
To be able to export the diagram as an image install npm and mermaid-cli on your computer
curl -sL https://deb.nodesource.com/setup_16.x | sudo -E bash -
sudo apt install nodejs
npm install -g @mermaid-js/mermaid-cli
Suppose you want to generate a graph that shows how a node it's relates to other nodes by topics, services, and actions. All you need to do is run the script:
ros2_graph your_node
This will print in the console a graph description in the mermaid language, then you have to copy and paste it on the node's readme and enjoy. But if you want export it to a file use the -o flag.
Example
ros2_graph /turtlesim -o turtle_diagram.md
You can also export the diagram as an image (png, svg or pdf) by setting the right file extension or using the flag --outputFormat:
ros2_graph /turtlesim -o turtle_diagram.png
ros2_graph /turtlesim -o turtle_diagram --outputFormat png
Note: you must copy everything between ```mermaid and ``` including both marks.
GitHub can display mermaid graphs. You can also display it on VS code by adding an extension in the devcontainer.json: "bierner.markdown-mermaid"
But what about nodes highly correlated as the range sensors, it does not make sense to have a graph for each node, Well don't worry you can include all the nodes that you want:
ros2_graph node_1 node_2 … node_n
Example:
ros2_graph /turtlesim /teleop_turtle
See an example graph:
flowchart LR
/turtle1/cmd_vel([/turtle1/cmd_vel<br>geometry_msgs/msg/Twist]):::topic --> /turtlesim
/teleop_turtle:::node --> /turtle1/cmd_vel
/turtlesim --> /turtle1/color_sensor([/turtle1/color_sensor<br>turtlesim/msg/Color]):::bugged
/turtlesim --> /turtle1/pose([/turtle1/pose<br>turtlesim/msg/Pose]):::bugged
/turtlesim o-.-o /clear[//clear<br>std_srvs/srv/Empty\]:::bugged
/turtlesim o-.-o /kill[//kill<br>turtlesim/srv/Kill\]:::bugged
/turtlesim o-.-o /reset[//reset<br>std_srvs/srv/Empty\]:::bugged
/turtlesim o-.-o /spawn[//spawn<br>turtlesim/srv/Spawn\]:::bugged
/turtlesim o-.-o /turtle1/set_pen[//turtle1/set_pen<br>turtlesim/srv/SetPen\]:::bugged
/turtlesim o-.-o /turtle1/teleport_absolute[//turtle1/teleport_absolute<br>turtlesim/srv/TeleportAbsolute\]:::bugged
/turtlesim o-.-o /turtle1/teleport_relative[//turtle1/teleport_relative<br>turtlesim/srv/TeleportRelative\]:::bugged
/turtle1/rotate_absolute{{/turtle1/rotate_absolute<br>turtlesim/action/RotateAbsolute}}:::action o==o /turtlesim
/teleop_turtle:::node <==> /turtle1/rotate_absolute
/turtlesim:::main_node
subgraph keys[<b>Keys<b/>]
subgraph nodes[<b><b/>]
topicb((No connected)):::bugged
main_node:::main_node
end
subgraph connection[<b><b/>]
node1:::node
node2:::node
node1 o-. to server .-o service[/Service<br>service/Type\]:::service
service <-. to client .-> node2
node1 -- publish --> topic([Topic<br>topic/Type]):::topic
topic -- subscribe --> node2
node1 o== to server ==o action{{/Action<br>action/Type/}}:::action
action <== to client ==> node2
end
end
classDef node opacity:0.9,fill:#2A0,stroke:#391,stroke-width:4px,color:#fff
classDef action opacity:0.9,fill:#66A,stroke:#225,stroke-width:2px,color:#fff
classDef service opacity:0.9,fill:#3B8062,stroke:#3B6062,stroke-width:2px,color:#fff
classDef topic opacity:0.9,fill:#852,stroke:#CCC,stroke-width:2px,color:#fff
classDef main_node opacity:0.9,fill:#059,stroke:#09F,stroke-width:4px,color:#fff
classDef bugged opacity:0.9,fill:#933,stroke:#800,stroke-width:2px,color:#fff
style keys opacity:0.15,fill:#FFF
style nodes opacity:0.15,fill:#FFF
style connection opacity:0.15,fill:#FFF
linkStyle 11,12,17,18 fill:none,stroke:green;
flowchart LR
/turtle1/cmd_vel([/turtle1/cmd_vel<br>geometry_msgs/msg/Twist]):::topic --> /turtlesim
/teleop_turtle:::node --> /turtle1/cmd_vel
/turtlesim --> /turtle1/color_sensor([/turtle1/color_sensor<br>turtlesim/msg/Color]):::bugged
/turtlesim --> /turtle1/pose([/turtle1/pose<br>turtlesim/msg/Pose]):::bugged
/turtlesim o-.-o /clear[//clear<br>std_srvs/srv/Empty\]:::bugged
/turtlesim o-.-o /kill[//kill<br>turtlesim/srv/Kill\]:::bugged
/turtlesim o-.-o /reset[//reset<br>std_srvs/srv/Empty\]:::bugged
/turtlesim o-.-o /spawn[//spawn<br>turtlesim/srv/Spawn\]:::bugged
/turtlesim o-.-o /turtle1/set_pen[//turtle1/set_pen<br>turtlesim/srv/SetPen\]:::bugged
/turtlesim o-.-o /turtle1/teleport_absolute[//turtle1/teleport_absolute<br>turtlesim/srv/TeleportAbsolute\]:::bugged
/turtlesim o-.-o /turtle1/teleport_relative[//turtle1/teleport_relative<br>turtlesim/srv/TeleportRelative\]:::bugged
/turtle1/rotate_absolute{{/turtle1/rotate_absolute<br>turtlesim/action/RotateAbsolute}}:::action o==o /turtlesim
/teleop_turtle:::node <==> /turtle1/rotate_absolute
/turtlesim:::main_node
subgraph keys[<b>Keys<b/>]
subgraph nodes[<b><b/>]
topicb((No connected)):::bugged
main_node:::main_node
end
subgraph connection[<b><b/>]
node1:::node
node2:::node
node1 o-. to server .-o service[/Service<br>service/Type\]:::service
service <-. to client .-> node2
node1 -- publish --> topic([Topic<br>topic/Type]):::topic
topic -- subscribe --> node2
node1 o== to server ==o action{{/Action<br>action/Type/}}:::action
action <== to client ==> node2
end
end
classDef node opacity:0.9,fill:#2A0,stroke:#391,stroke-width:4px,color:#fff
classDef action opacity:0.9,fill:#66A,stroke:#225,stroke-width:2px,color:#fff
classDef service opacity:0.9,fill:#3B8062,stroke:#3B6062,stroke-width:2px,color:#fff
classDef topic opacity:0.9,fill:#852,stroke:#CCC,stroke-width:2px,color:#fff
classDef main_node opacity:0.9,fill:#059,stroke:#09F,stroke-width:4px,color:#fff
classDef bugged opacity:0.9,fill:#933,stroke:#800,stroke-width:2px,color:#fff
style keys opacity:0.15,fill:#FFF
style nodes opacity:0.15,fill:#FFF
style connection opacity:0.15,fill:#FFF
linkStyle 11,12,17,18 fill:none,stroke:green;