ros2-web-integration

What this skill does

# ROS2 Web Integration Skill

## When to Use This Skill
- Building a web dashboard to monitor or control a robot running ROS2
- Streaming camera feeds (MJPEG, WebRTC, compressed WebSocket) from a robot to a browser
- Exposing ROS2 services and actions as REST API endpoints
- Implementing bidirectional WebSocket communication between a web UI and ROS2 nodes
- Setting up rosbridge_suite for quick prototyping or foxglove integration
- Writing a custom FastAPI or Flask bridge to ROS2 for production deployments
- Adding authentication, rate limiting, or CORS to robot web interfaces
- Running an async web server (uvicorn) alongside the rclpy executor without deadlocks
- Publishing teleop commands from a browser joystick to cmd_vel
- Serving ROS2 parameter configuration pages or diagnostic dashboards over HTTP

## Architecture Overview

### Comparison Table

| Feature | rosbridge_suite | Custom FastAPI Bridge | Custom Flask Bridge |
|---|---|---|---|
| Latency | ~5-15ms (WebSocket) | ~2-5ms (WebSocket), ~10-30ms (REST) | ~10-50ms (REST only without extensions) |
| Throughput | Medium (JSON serialization overhead) | High (binary WebSocket, async) | Low-Medium (sync, GIL-bound) |
| Auth | Basic (rosauth, limited) | Full (JWT, OAuth2, API keys) | Full (Flask-Login, JWT) |
| Complexity | Low (launch and connect) | Medium (must manage two event loops) | Medium (must manage threading) |
| Video Streaming | Requires separate web_video_server | Native (MJPEG, WebSocket binary) | MJPEG via generator responses |
| Production Ready | No (exposes full topic graph) | Yes | Yes (with gunicorn) |
| When to Use | Prototyping, foxglove, quick demos | Production APIs, high-perf streaming | Simple internal tools, legacy systems |

### When to Use rosbridge vs Custom Bridge

Use **rosbridge_suite** when:
- You need a working bridge in under 10 minutes
- The client is foxglove, webviz, or another rosbridge-aware tool
- Security is not a concern (local network, demo environment)
- You do not need custom business logic between web and ROS2

Use a **custom bridge** (FastAPI/Flask) when:
- You need authentication, authorization, or rate limiting
- You want to expose only specific topics/services (not the entire ROS2 graph)
- You need to transform or aggregate data before sending to the client
- You need REST endpoints for integration with non-WebSocket clients
- You are streaming video and need control over encoding and quality
- The system is deployed in production or on a public network

## Pattern 1: rosbridge_suite

### Installation and Launch

```bash
# Install rosbridge_suite
sudo apt install ros-${ROS_DISTRO}-rosbridge-suite

# Launch with default settings (port 9090)
ros2 launch rosbridge_server rosbridge_websocket_launch.xml

# Launch with custom port and SSL
ros2 launch rosbridge_server rosbridge_websocket_launch.xml \
    port:=9091 \
    ssl:=true \
    certfile:=/etc/ssl/certs/robot.pem \
    keyfile:=/etc/ssl/private/robot.key

# Launch with authentication (rosauth)
ros2 launch rosbridge_server rosbridge_websocket_launch.xml \
    authenticate:=true
```

### JavaScript Client (roslibjs)

```javascript
// Connect to rosbridge WebSocket
const ros = new ROSLIB.Ros({ url: 'ws://robot-host:9090' });

ros.on('connection', () => console.log('Connected to rosbridge'));
ros.on('error', (err) => console.error('Connection error:', err));
ros.on('close', () => console.log('Connection closed'));

// Subscribe to compressed camera images
const imageTopic = new ROSLIB.Topic({
  ros: ros,
  name: '/camera/image/compressed',
  messageType: 'sensor_msgs/msg/CompressedImage',
  // Throttle to 10 Hz to avoid flooding the browser
  throttle_rate: 100,
  // Queue size of 1 — drop stale frames
  queue_size: 1
});

imageTopic.subscribe((msg) => {
  // msg.data is base64-encoded JPEG
  const imgElement = document.getElementById('camera-feed');
  imgElement.src = 'data:image/jpeg;base64,' + msg.data;
});

// Call a ROS2 service
const getMapSrv = new ROSLIB.Service({
  ros: ros,
  name: '/map_server/map',
  serviceType: 'nav_msgs/srv/GetMap'
});

getMapSrv.callService(new ROSLIB.ServiceRequest({}), (result) => {
  console.log('Map received:', result.map.info.width, 'x', result.map.info.height);
}, (error) => {
  console.error('Service call failed:', error);
});

// Publish velocity commands from a virtual joystick
const cmdVelTopic = new ROSLIB.Topic({
  ros: ros,
  name: '/cmd_vel',
  messageType: 'geometry_msgs/msg/Twist'
});

function sendVelocity(linearX, angularZ) {
  const twist = new ROSLIB.Message({
    linear: { x: linearX, y: 0.0, z: 0.0 },
    angular: { x: 0.0, y: 0.0, z: angularZ }
  });
  cmdVelTopic.publish(twist);
}

// Publish at 10 Hz while joystick is active; stop on release
let joystickInterval = null;
function onJoystickMove(lx, az) {
  if (!joystickInterval) {
    joystickInterval = setInterval(() => sendVelocity(lx, az), 100);
  }
}
function onJoystickRelease() {
  clearInterval(joystickInterval);
  joystickInterval = null;
  sendVelocity(0.0, 0.0);  // Always send zero on release
}
```

### Limitations and Performance
- **JSON serialization overhead**: All messages are serialized to JSON, including binary data (base64-encoded). A 640x480 JPEG compressed image becomes ~30% larger over the wire.
- **No topic filtering**: By default rosbridge exposes every topic, service, and action on the ROS2 graph. Any connected client can publish to `/cmd_vel`.
- **Single-threaded event loop**: rosbridge_server uses a single Tornado event loop. High-frequency subscriptions from multiple clients can starve the loop.
- **No built-in rate limiting**: Clients can subscribe at any rate. A misbehaving client subscribing to a 30Hz point cloud will consume the server.
- **Authentication is minimal**: rosauth uses MAC-based tokens with shared secrets. It does not support JWT, OAuth2, or role-based access.

## Pattern 2: Custom FastAPI Bridge

### Project Structure

```
robot_web_bridge/
├── robot_web_bridge/
│   ├── __init__.py
│   ├── ros_node.py          # ROS2 node with shared state
│   ├── web_app.py           # FastAPI application
│   ├── main.py              # Entry point: starts both rclpy and uvicorn
│   ├── auth.py              # JWT authentication middleware
│   └── rate_limiter.py      # Token bucket rate limiter
├── config/
│   └── bridge_config.yaml   # Allowed topics, rate limits, auth keys
├── launch/
│   └── web_bridge.launch.py
├── package.xml
├── setup.py
└── setup.cfg
```

### ROS2 Node with Async Executor

```python
# ros_node.py
import threading
import time
from typing import Optional

import rclpy
from rclpy.node import Node
from rclpy.executors import MultiThreadedExecutor
from rclpy.qos import QoSProfile, ReliabilityPolicy, HistoryPolicy
from sensor_msgs.msg import CompressedImage
from geometry_msgs.msg import Twist
from nav_msgs.msg import Odometry
from std_srvs.srv import Trigger


class RobotBridgeNode(Node):
    """ROS2 node that exposes topic data via thread-safe shared state."""

    def __init__(self):
        super().__init__('web_bridge_node')

        # Thread-safe shared state for latest messages
        self._lock = threading.Lock()
        self._latest_image: Optional[bytes] = None
        self._latest_odom: Optional[dict] = None
        self._image_timestamp: float = 0.0

        # QoS for sensor data — best effort, keep last 1
        sensor_qos = QoSProfile(
            reliability=ReliabilityPolicy.BEST_EFFORT,
            history=HistoryPolicy.KEEP_LAST,
            depth=1
        )

        # Subscribers
        self.create_subscription(
            CompressedImage, '/camera/image/compressed',
            self._image_cb, sensor_qos)
        self.create_subscription(
            Odometry, '/odom', self._odom_cb, sensor_qos)

        # Publisher for velocity commands
        self.cmd_vel_pub = self.create_publisher(Twist, '/cmd_vel', 10)

        # Service client for emergency stop
        self.estop_client = self.create_client(Trigger, '/emergency_st