ros2/rmw_zenoh

What it solves

rmw_zenoh provides a ROS 2 Middleware (RMW) implementation based on Zenoh, offering an alternative to the default DDS-based communication layers. It simplifies discovery and communication across different hosts, containers, and networks, while providing high-performance options for local communication.

How it works

It uses the zenoh-cpp bindings to implement the ROS 2 RMW interface. The system relies on Zenoh sessions and an optional Zenoh router to manage discovery and message routing.

Key mechanisms include:

• Zenoh Router: Acts as a central point for discovery and gossip, allowing nodes to find each other without relying on multicast discovery (which is disabled by default).
• Shared Memory (SHM): Provides implicit optimization for messages passing between local nodes, reducing latency and CPU usage for large payloads by writing data to a shared memory segment instead of using the network stack.
• Serialization Buffer Pool: Recycles buffers during transmission to bound memory usage and improve efficiency.
• Configuration: Uses .json5 configuration files and environment variable overrides to manage session behavior, router endpoints, and security settings.

Who it’s for

Robotics developers using ROS 2 who need a flexible, high-performance communication middleware, particularly those operating across multiple hosts or within Docker containers.

Highlights

• Implicit Shared Memory: Transparently optimizes local communication for large payloads without requiring specific API calls.
• Flexible Discovery: Supports both router-based discovery and multicast scouting for peer-to-peer discovery.
• Cross-Host Bridging: Simplifies connecting ROS 2 nodes across different machines via Zenoh routers.
• Integrated Security: Supports access control, authentication, and encryption through zenoh_security_tools.
• Memory Efficiency: Implements a buffer pool to recycle serialization buffers and prevent uncontrolled memory growth.