ros2-engineering-skills

name ros2-engineering-skills description Comprehensive ROS 2 engineering guide covering workspace setup, node architecture, communication patterns (topics/services/actions with QoS), lifecycle and component nodes, launch composition, tf2/URDF, ros2_control hardware interfaces, real-time constraints, Nav2, MoveIt 2, perception pipelines, simulation (Gazebo/Isaac Sim), security (SROS2/DDS), micro-ROS (MCU/RTOS), multi-robot systems (fleet management/Open-RMF), testing, debugging, deployment, and ROS 1 migration. Trigger whenever the user works on ROS 2 code, packages, launch files, URDF/xacro, DDS configuration, ros2_control, Nav2, MoveIt 2, or any robotics middleware task involving rclcpp, rclpy, colcon, ament, rosbag2, ros2 CLI tools, Gazebo/Isaac Sim, micro-ROS, SROS2, or multi-robot coordination. Also trigger for ROS 1 to ROS 2 migration, cross-compilation, Docker-based ROS 2 workflows, and CI/CD for robotics. ROS 2 Engineering Skills A progressive-disclosure skill for ROS 2 development — from first workspace to production fleet deployment. Each section below gives you the essential decision framework; detailed patterns, code templates, and anti-patterns live in the references/ directory. Read the relevant reference file before writing code. How to use this skill Identify what the user is building (see Decision Router below). Read the matching references/*.md file for detailed guidance. Apply the Core Engineering Principles in every piece of code you generate. When multiple domains intersect (e.g. Nav2 + ros2_control), read both files. Decision router User is doing... Read Creating a workspace, package, or build config references/workspace-build.md Writing nodes, executors, callback groups references/nodes-executors.md Topics, services, actions, custom interfaces, QoS references/communication.md Lifecycle nodes, component loading, composition references/lifecycle-components.md Launch files, conditional logic, event handlers references/launch-system.md tf2, URDF, xacro, robot_state_publisher references/tf2-urdf.md ros2_control, hardware interfaces, controllers references/hardware-interface.md Real-time constraints, PREEMPT_RT, memory, jitter references/realtime.md Nav2, SLAM, costmaps, behavior trees references/navigation.md MoveIt 2, planning scene, grasp pipelines references/manipulation.md Camera, LiDAR, PCL, cv_bridge, depth processing references/perception.md Unit tests, integration tests, launch_testing, CI references/testing.md ros2 doctor, tracing, profiling, rosbag2 references/debugging.md Docker, cross-compile, fleet deployment, OTA references/deployment.md Gazebo, Isaac Sim, sim-to-real, use_sim_time references/simulation.md SROS2, DDS security, certificates, supply chain references/security.md micro-ROS, MCU/RTOS, XRCE-DDS, rclc references/micro-ros.md Multi-robot fleet, Open-RMF, DDS discovery scale references/multi-robot.md Message types, units, covariance, frame conventions references/message-types.md ROS 1 migration, ros1_bridge, hybrid operation references/migration-ros1.md When a task spans multiple domains, read all relevant files and reconcile conflicting recommendations by favoring safety, then determinism, then simplicity. Cross-cutting concern — Security: Security is not isolated to references/security.md . Every domain should consider its security implications: hardware interfaces need safe shutdown on auth failure, DDS topics may need encryption, deployment images need supply chain verification, and fleet communication must use TLS. When reviewing code in any domain, check whether the data path crosses a trust boundary. Core engineering principles These apply to every ROS 2 artifact you produce, regardless of domain. 1. Distro awareness Always ask which ROS 2 distribution the user targets. Key differences: Feature Foxy ( EOL ) Humble (LTS) Jazzy (LTS) Kilted (non-LTS) Rolling EOL Jun 2023 ( ended ) May 2027 May 2029 Nov 2025 Rolling Ubuntu 20.04 22.04 24.04 24.04 Latest Default DDS Fast DDS Fast DDS Fast DDS Fast DDS Fast DDS Zenoh support — — — Tier 1 Tier 1 Type description support No No Yes Yes Yes Service introspection No No Yes Yes Yes EventsExecutor No No Experimental Stable (+ rclpy) Stable (+ rclpy) Default bag format sqlite3 sqlite3 MCAP MCAP MCAP ros2_control interface N/A (separate) 2.x 4.x 4.x Latest CMake recommendation ament_target_deps ament_target_deps either target_link_libs target_link_libs When the user does not specify, default to the latest LTS (Jazzy). Pin the exact distro in Dockerfile, CI, and documentation so builds are reproducible. 2. C++ vs Python decision Choose the language based on the node's role, not personal preference. Use rclcpp (C++) when: The node sits in a control loop running ≥100 Hz Deterministic memory allocation matters (real-time path) The node is a hardware driver or controller plugin Intra-process zero-copy communication is required Use rclpy (Python) when: The node is orchestration, monitoring, or parameter management Rapid prototyping with frequent iteration Heavy use of ML frameworks (PyTorch, TensorFlow) that are Python-native The node does not sit in a latency-critical path Mixed stacks are normal. A typical robot has C++ drivers/controllers and Python orchestration/monitoring. Note: component_container (composition) only loads C++ components via pluginlib. Python nodes run as separate processes, but can share a launch file and communicate via zero-overhead intra-host DDS. Intra-process communication works for any nodes sharing a process — not only composable components. Any nodes instantiated in the same process with use_intra_process_comms(true) can use zero-copy transfer. 3. Package structure conventions Every package should follow this layout. Consistency across a workspace reduces onboarding time and makes CI scripts portable. my_package/ ├── CMakeLists.txt # or setup.py for pure Python ├── package.xml # format 3, with <depend> tags ├── config/ │ └── params.yaml # default parameters ├── launch/ │ └── bringup.launch.py # Python launch file ├── include/my_package/ # C++ public headers (if library) ├── src/ # C++ source files ├── my_package/ # Python modules (if ament_python or mixed) ├── test/ # gtest, pytest, launch_testing ├── urdf/ # URDF/xacro (if applicable) ├── msg/ srv/ action/ # custom interfaces (dedicated _interfaces package preferred) └── README.md Separate interface definitions into a *_interfaces package so downstream packages can depend on interfaces without pulling in implementation. 4. Parameter discipline Declare every parameter with a type, description, range, and default in the node constructor — never use undeclared parameters. Use ParameterDescriptor with FloatingPointRange or IntegerRange for numeric bounds. The parameter server rejects out-of-range values at set time. Group related parameters under a namespace prefix: controller.kp , controller.ki , controller.kd . Load defaults from a config/params.yaml ; allow launch-time overrides. For dynamic reconfiguration, register a set_parameters_callback and validate new values atomically before accepting. 5. Error handling philosophy Nodes must not silently swallow errors. Log at the appropriate severity, then take a safe action (stop motion, request help, transition to error state). Prefer lifecycle node error transitions over ad-hoc boolean flags. When calling a service, always handle the "service not available" and "future timed out" cases explicitly. For hardware drivers, distinguish transient errors (retry with backoff) from fatal errors (transition to FINALIZED and alert the operator). 6. Quality of Service defaults Start from these profiles and adjust per use case: Use case Reliability Durability History Depth Deadline Lifespan Sensor stream BEST_EFFORT VOLATILE KEEP_LAST 5 — — Command velocity RELIABLE VOLATILE KEEP_LAST 1 100 ms 200 ms Map (latched) RELIABLE TRANSIENT_LOCAL KEEP_LAST 1 — — Diagnostics RELIABLE VOLATILE KEEP_LAST 10 — — Parameter events RELIABLE VOLATILE KEEP_LAST 1000 — — Action feedback RELIABLE VOLATILE KEEP_LAST 1 — — Safety heartbeat RELIABLE VOLATILE KEEP_LAST 1 500 ms 1 s QoS mismatches are the #1 cause of "I published but nobody receives." Always check compatibility with ros2 topic info -v when debugging. DEADLINE and LIFESPAN are critical for safety-critical systems. DEADLINE fires an event when no message arrives within the specified period (detect stale data). LIFESPAN discards messages older than the specified duration before delivery (prevent acting on stale data). See references/communication.md section 9 for full API and examples. 7. Naming conventions Entity Convention Example Package snake_case arm_controller Node snake_case joint_state_broadcaster Topic /snake_case with ns /arm/joint_states Service /snake_case /arm/set_mode Action /snake_case /arm/follow_joint_trajectory Parameter snake_case with dot ns controller.publish_rate Frame snake_case base_link , camera_optical Interface PascalCase.msg/srv/action JointState.msg 8. Thread safety and callbacks A MutuallyExclusiveCallbackGroup serializes its callbacks — safe for shared state without locks, but limits throughput. A ReentrantCallbackGroup allows parallel execution — you must protect shared state with std::mutex (C++) or threading.Lock (Python). Calling a service from a callback: The service client must be in a separate MutuallyExclusiveCallbackGroup from the calling callback. Otherwise the executor deadlocks — the callback waits for the response while the executor cannot deliver it. Always use async_send_request with a response callback; never use spin_until_future_complete inside an executor callback. Never do blocking work (file I/O, long computation, sleep ) inside a timer or subscription callback on the default executor. Offload to a dedicated thread or use a MultiThreadedExecutor with a reentrant group. In rclcpp, prefer std::shared_ptr<const MessageT> in subscription callbacks to avoid unnecessary copies and enable zero-copy intra-process. 9. Lifecycle-first design Default to lifecycle (managed) nodes for anything that owns resources: hardware drivers, sensor pipelines, planners, controllers. ┌──────────────┐ create() ──► │ Unconfigured │ └──────┬───────┘ on_configure │ ┌──────▼───────┐ │ Inactive │ └──────┬───────┘ on_activate │ ┌──────▼───────┐ │ Active │ └──────┬───────┘ on_deactivate │ ┌──────▼───────┐ │ Inactive │ └──────┬───────┘ on_cleanup │ ┌──────▼───────┐ │ Unconfigured │ └──────┬───────┘ on_shutdown │ ┌──────▼───────┐ │ Finalized │ └───────────────┘ This gives the system manager (launch file, orchestrator, or operator) explicit control over when resources are allocated, when the node starts processing, and how it shuts down. It also makes error recovery predictable. 10. Build and CI hygiene Use colcon build --cmake-args -DCMAKE_BUILD_TYPE=RelWithDebInfo for development; Release for deployment. Enable -Wall -Wextra -Wpedantic and treat warnings as errors in CI. Run colcon test with --event-handlers console_cohesion+ so test output groups by package. Pin rosdep keys in rosdep.yaml for reproducible dependency resolution. Cache /opt/ros/ , .ccache/ , and build/ / install/ in CI to cut build times by 60–80%. Common anti-patterns Anti-pattern Why it hurts Fix Global variables for node state Breaks composition, untestable Store state as class members spin() in main() for multi-node processes Starves other nodes Use MultiThreadedExecutor or component composition Hardcoded topic names Breaks reuse across robots Use relative names + namespace remapping KEEP_ALL history with no bound Memory grows unbounded on slow subscribers Use KEEP_LAST with explicit depth Using time.sleep() / std::this_thread::sleep_for Blocks the executor thread Use create_wall_timer or a dedicated thread Monolithic launch file for everything Unmanageable past 10 nodes Compose launch files with IncludeLaunchDescription Skipping package.xml dependencies Builds locally, breaks CI and Docker Declare every dependency explicitly Publishing in constructor Subscribers may not be ready, messages lost Publish in on_activate or after a short timer Ignoring QoS compatibility Silent communication failure Match publisher/subscriber QoS or check with ros2 topic info -v Creating timers/subs in callbacks Resource leak, unpredictable behavior Create all entities in constructor or on_configure Synchronous service call in callback Deadlocks the executor thread Use async_send_request with a callback or dedicated thread Service client in same callback group as caller Deadlocks even with async in MultiThreadedExecutor Put service client in a separate MutuallyExclusiveCallbackGroup No safe command on shutdown Motors hold last velocity after node exits Send zero-velocity in on_deactivate AND destructor (see references/hardware-interface.md ) Dynamic subscriptions with StaticSingleThreadedExecutor New subs are never picked up after spin() Use SingleThreadedExecutor or MultiThreadedExecutor for dynamic entities CPU frequency governor left on powersave / ondemand 10-100 ms latency spikes in RT path Set performance governor, disable turbo boost (see references/realtime.md ) Distro-specific migration notes When upgrading between distributions, check these breaking changes first: Foxy → Humble: Complete API overhaul. Foxy packages require significant rework. ros2_control was not bundled in Foxy — must be built separately. Lifecycle node API stabilized in Humble. Action server/client API changed significantly. Humble → Jazzy: ros2_control API changed from 2.x to 4.x — export_state_interfaces() and export_command_interfaces() are now auto-generated by the framework. Manual overrides use on_export_state_interfaces() . See references/hardware-interface.md . Handle get_value() deprecated → use get_optional<T>() on LoanedStateInterface / LoanedCommandInterface (controller side). Hardware interfaces use set_state() /