Zenoh's DDS Connector
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More recent information can be found on the zenoh website.
The Data Distribution Service (DDS) is a standard for data-centric publish subscribe. Whilst DDS has been around for quite some time and has a long history of deployments in various industries, it has recently gained quite a bit of attentions thanks to its adoption by the Robotic Operating System (ROS2) -- where it is used for communication between ROS2 nodes.
As mentioned above, ROS2 has adopted DDS as the mechanism to exchange data between nodes within and potentially across a robot. That said, due to some of the very core assumptions at the foundations of the DDS wire-protocol, beside the fact that it leverage UDP/IP multicast for communication, it is not so straightforward to scale DDS communication over a WAN or across multiple LANs. Zenoh, on the other hand was designed since its inception to operate at Internet Scale.
Thus, the main motivations to have a DDS connector for zenoh are:
- Facilitate the interconnection of robot swarms.
- Support use cases of edge robotics.
- Give the possibility to use zenoh's geo-distributed storage and query system to better manage robot's data.
zenoh routers provide a plug-in mechanism that allow for extensions to be loaded and activated by its management API. Thus the most natural way to implement a DDS connector for zenoh is to do that as a zenoh router plugin.
This plugin, will essentially:
- Spoof DDS discovery data and transparently expose DDS writers/readers as zenoh publisher/subscribers
- Route the data produced by discovered DDS writers to data to matching entities.
The mapping between DDS and zenoh is rather straightforward. Given a DDS Reader/Writer for topic A in a given partition P with a set of QoS Q, then the equivalent zenoh resource will be named as P/A/*. On the other hand actual writes will be on the resource P/A/sample-key-hash as this allows for zenoh subscriber to easily subscribe to just a specific Topic instance, a set of them or of all of them.
Zenoh's DDS Plugin is available on the zenoh-plugin-dds repository. Take a look at the repository readme to learn how to get started.