rmw_zenoh

rmw_zenoh provides an experimental implementation of the ROS middleware interface using Eclipse Zenoh as the middleware. The RMW implementation is contained in the rmw_zenoh_cpp package.

Note that this implementation is currently very young, under heavy development, and generally rapidly changing. It may work smoothly, or it may blow up and squash your cat. Please do not expect to use it except in an experimental capacity.

Zenoh does not include its own serialisation scheme. Currently a hacked-up copy of Fast CDR is used. In the future we hope to support different serialisation schemes, possibly in a configurable way.

Installation

Set up a new workspace using the provided rmw_zenoh.repos file.

mkdir -p ~/rmw_zenoh_ws/src
cd ~/rmw_zenoh_ws
wget https://raw.githubusercontent.com/osrf/rmw_zenoh/main/rmw_zenoh.repos
vcs import src < rmw_zenoh.repos

Next, prepare your environment for compiling Zenoh. The rmw_zenoh_cpp package depends on the zenoh_vendor package to pull in Zenoh. zenoh_vendor provides the Zenoh foreign function interface (for C) library from the Rust implementation of Zenoh. The library is obtained by cloning and compiling the Zenoh source code from GitHub. Because it will compile Zenoh automatically, you must meet the preconditions for compiling Zenoh. Most importantly, you must use the nightly version of the Rust toolchain. Install Rust using rustup, then run the following command to enable it.

rustup default nightly

Next, ensure all the dependencies of the packages in the rmw_zenoh_ws are available.

cd ~/rmw_zenoh_ws
rosdep install --ignore-src --from-paths src --rosdistro=foxy -y

You are now ready to compile the workspace. Because of an as-yet unresolved quirk in the typesupport compilation (ros2#39), this needs to be done twice.

cd ~/rmw_zenoh_ws
colcon build
source install/setup.bash
colcon build --cmake-force-configure

Testing

You can test rmw_zenoh_cpp using the existing ROS 2 sample nodes.

Open two terminals and source the rmw_zenoh_ws workspace in each one. Then, in each terminal, change the active RMW implementation to rmw_zenoh_cpp using the RMW_IMPLEMENTATION environment variable. (See this tutorial for more information on changing your active RMW implementation.) Then, launch the demonstration publisher and subscriber nodes, one in each terminal.

Terminal 1:

cd ~/rmw_zenoh_ws
source install/setup.bash
export RMW_IMPLEMENTATION=rmw_zenoh_cpp
ros2 run demo_nodes_cpp talker

Terminal 2:

cd ~/rmw_zenoh_ws
source install/setup.bash
export RMW_IMPLEMENTATION=rmw_zenoh_cpp
ros2 run demo_nodes_cpp listener

You should see data being transmitted from the talker program to the listener program. You may also see various informational messages from the rmw_zenoh_cpp implementation. Most of these are temporary aides to development, but they do indicate that the correct RMW implementation is being used.