nodelet

A nodelet is a software package in the Robot Operating System (ROS) designed to run multiple nodes within a single process. This approach offers significant advantages, particularly in performance-critical applications where inter-process communication overhead can become a bottleneck. Traditional ROS nodes communicate using message passing, which involves serialization and deserialization of data and inter-process communication mechanisms. Nodelets, by contrast, allow these nodes to share memory directly, eliminating this overhead.

The core concept behind nodelets is that they are dynamically loadable libraries that can be instantiated as separate "nodes" within a single C++ process. This means that multiple nodelets can be launched together and communicate with each other extremely efficiently. This is especially beneficial for tasks involving high-bandwidth data streams, such as image processing or sensor fusion, where the latency and computational cost of standard ROS communication can be prohibitive.

Developers typically package related functionalities into a single nodelet manager, which then loads and runs individual nodelet plugins. This allows for flexible deployment and management of computational resources. While offering performance gains, nodelets also introduce some complexities. For example, error handling and debugging can be more challenging as a crash in one nodelet can bring down the entire process. Despite these considerations, nodelets are a powerful tool for optimizing ROS applications that demand high performance and low latency.