/ros2

name: ros2-development
description: >
  Comprehensive best practices, design patterns, and common pitfalls for ROS2 (Robot Operating System 2)
  development. Use this skill when building ROS2 nodes, packages, launch files, components, or debugging
  ROS2 systems. Trigger whenever the user mentions ROS2, colcon, rclpy, rclcpp, DDS, QoS, lifecycle nodes,
  managed nodes, ROS2 launch, ROS2 parameters, ROS2 actions, nav2, MoveIt2, micro-ROS, or any ROS2-era
  robotics middleware. Also trigger for ROS2 workspace setup, DDS tuning, intra-process communication,
  ROS2 security, or deploying ROS2 in production. Also trigger for colcon build issues, ament_cmake,
  ament_python, CMakeLists.txt for ROS2, package.xml dependencies, rosdep, workspace overlays, custom
  message generation, or ROS2 build troubleshooting. Covers Humble, Iron, Jazzy, and Rolling distributions.

ROS2 Development Skill

When to Use This Skill

• Building ROS2 packages, nodes, or component containers
• Setting up colcon workspaces, ament_cmake, or ament_python packages
• Writing CMakeLists.txt, package.xml, or setup.py for ROS2
• Defining custom messages, services, or actions
• Writing Python launch files with conditional logic
• Configuring DDS middleware and QoS profiles
• Implementing lifecycle (managed) nodes
• Working with Nav2, MoveIt2, or other ROS2 frameworks
• Debugging DDS discovery, QoS mismatches, or build failures
• Deploying ROS2 to production or embedded systems (micro-ROS)
• Setting up CI/CD for ROS2 packages

Core Architecture

1. Node Design Patterns

**Basic Node (rclpy)**:

#!/usr/bin/env python3
import rclpy
from rclpy.node import Node
from rclpy.qos import QoSProfile, ReliabilityPolicy, HistoryPolicy
from std_msgs.msg import String

class PerceptionNode(Node):
    def __init__(self):
        super().__init__('perception_node')

        # 1. Declare parameters with types and descriptions
        self.declare_parameter('rate_hz', 30.0,
            descriptor=ParameterDescriptor(
                description='Processing rate in Hz',
                floating_point_range=[FloatingPointRange(
                    from_value=1.0, to_value=120.0, step=0.0
                )]
            ))
        self.declare_parameter('confidence_threshold', 0.7)
        self.declare_parameter('frame_id', 'camera_link')

        # 2. Read parameters
        rate_hz = self.get_parameter('rate_hz').value
        self.threshold = self.get_parameter('confidence_threshold').value
        self.frame_id = self.get_parameter('frame_id').value

        # 3. Set up QoS profiles
        sensor_qos = QoSProfile(
            reliability=ReliabilityPolicy.BEST_EFFORT,
            history=HistoryPolicy.KEEP_LAST,
            depth=1
        )
        reliable_qos = QoSProfile(
            reliability=ReliabilityPolicy.RELIABLE,
            history=HistoryPolicy.KEEP_LAST,
            depth=10
        )

        # 4. Publishers first, then subscribers
        self.det_pub = self.create_publisher(
            DetectionArray, 'detections', reliable_qos)

        self.image_sub = self.create_subscription(
            Image, 'camera/image_raw', self.image_callback, sensor_qos)

        # 5. Timers for periodic work
        self.timer = self.create_timer(1.0 / rate_hz, self.timer_callback)

        # 6. Parameter change callback
        self.add_on_set_parameters_callback(self.param_callback)

        self.get_logger().info(
            f'Perception node started at {rate_hz}Hz, '
            f'threshold={self.threshold}')

    def param_callback(self, params):
        """Handle runtime parameter changes (replaces dynamic_reconfigure)"""
        for param in params:
            if param.name == 'confidence_threshold':
                self.threshold = param.value
                self.get_logger().info(f'Threshold updated to {param.value}')
        return SetParametersResult(successful=True)

    def image_callback(self, msg):
        # Process incoming images
        pass

    def timer_callback(self):
        # Periodic work
        pass

def main(args=None):
    rclpy.init(args=args)
    node = PerceptionNode()
    try:
        rclpy.spin(node)
    except KeyboardInterrupt:
        pass
    finally:
        node.destroy_node()
        rclpy.shutdown()

if __name__ == '__main__':
    main()

**Basic Node (rclcpp)**:

#include <rclcpp/rclcpp.hpp>
#include <sensor_msgs/msg/image.hpp>
#include <vision_msgs/msg/detection2_d.hpp>
#include <memory>

class PerceptionNode : public rclcpp::Node {
public:
    PerceptionNode() : Node("perception_node") {
        // Declare and get parameters
        this->declare_parameter("rate_hz", 30.0);
        this->declare_parameter("confidence_threshold", 0.7);
        double rate_hz = this->get_parameter("rate_hz").as_double();

        // QoS
        auto sensor_qos = rclcpp::SensorDataQoS();
        auto reliable_qos = rclcpp::QoS(10).reliable();

        // Publishers and subscribers
        det_pub_ = this->create_publisher<vision_msgs::msg::Detection2D>("detections", reliable_qos);
        image_sub_ = this->create_subscription<sensor_msgs::msg::Image>(
            "camera/image_raw", sensor_qos, [this](const std::shared_ptr<const sensor_msgs::msg::Image>& msg){
                this->image_callback(msg);
            });

        timer_ = this->create_wall_timer(
            std::chrono::milliseconds(static_cast<int>(1000.0 / rate_hz)),
            [this](){ this->timer_callback(); });

        RCLCPP_INFO(this->get_logger(), "Perception node started at %.1fHz", rate_hz);
    }

private:
    void image_callback(const std::shared_ptr<const sensor_msgs::msg::Image>& msg) {
        // Use shared_ptr for zero-copy potential
    }
    void timer_callback() {}

    rclcpp::Publisher<vision_msgs::msg::Detection2D>::SharedPtr det_pub_;
    rclcpp::Subscription<sensor_msgs::msg::Image>::SharedPtr image_sub_;
    rclcpp::TimerBase::SharedPtr timer_;
};

int main(int argc, char** argv) {