This repo shows few different ways to deal with ROS 2 node interconnectivity depending whether you:
- use nodes on a single machine or on multiple machines
- use nodes with or without docker
- connect ROS 2 nodes over LAN or WAN
To focus purely on connectivity, not on running fancy ROS 2 software or robots in Gazebo, I will go through different scenarios based on a simple ROS 2 system containing of 3 nodes:
/turtlesim- a very simple, simulator for learning ROS where you simulate ... a turtle :)/move_controller- node for controlling the movement of the turtle/color_controller- node that is changing the color of the line drawn by a turtle each second
The solution is scalable, so what you will learn can be applied in very complex distributed ROS 2 systems as well!
Below, there are 4 example use cases using the same code base, launched in different architecture scenarios.
Make sure you have Docker and Docker-Compose installed on your laptop.
The official instruction is the best tutorial but here's a quick rundown for you (for Linux):
sudo -E apt-get -y install apt-transport-https ca-certificates software-properties-common && \
curl -sL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add - && \
arch=$(dpkg --print-architecture) && \
sudo -E add-apt-repository "deb [arch=${arch}] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" && \
sudo -E apt-get update && \
sudo -E apt-get -y install docker-ce docker-composesudo systemctl daemon-reload
sudo systemctl restart dockerROS 2 Foxy installed on your laptop is needed only for [Eg. 0] section.
cd ros2_ws
colcon build
source /opt/ros/foxy/setup.bash
source install/setup.bash # full path might be: ~/ros2_docker_examples/ros2_ws/install/setup.bash
ros2 launch my_turtle_bringup turtlesim_demo.launch.py
Please stay in ros2_docker_examples/ directory while executing those commands:
sudo chmod +x eg1/ros_entrypoint.sh
docker build -t turtle_demo -f eg1/Dockerfile .
xhost local:root
sudo docker run --rm -it \
--env DISPLAY \
--volume /tmp/.X11-unix:/tmp/.X11-unix:rw \
turtle_demo \
ros2 launch my_turtle_bringup turtlesim_demo.launch.py
cd eg2
docker-compose up --build
Because two ROS 2 devices are in different networks, DDS can not perform auto-discovery.
Also devices can not reach each other because they do not have neither public nor static IP addresses and are behind Wi-Fi router NAT.
Ready to use example is available in eg3/ folder. There are two separate subfolders with a docker-compose.yml file which should be launched on two separate devices from different networks.
At first modify eg3/dev1/.env and eg3/dev2/.env files by providing the same Husarnet network Join Code there.
JOINCODE=fc94:b01d:1803:8dd8:b293:5c7d:7639:932a/xxxxxxxxxxxxxxxxxxxxxx
HOSTNAME=turtle-controller
You will find your Join Code at https://app.husarnet.com
-> Click on the desired network
-> Add element button
-> Join Code tab
- Start the first device:
cd eg3/dev1
docker-compose up --buildAfter a while you should see your first device connected to the Husarnet network:
- Add the first device address to Peers list of the second device, by editing:
eg3/dev2/cyclonedds.xmlfile:
...
<Discovery>
<Peers>
<Peer address="fc94:bc6f:1c91:51d:b6b0:1702:290c:7ab7"/>
</Peers>
<ParticipantIndex>auto</ParticipantIndex>
</Discovery>
...- Start the second device:
cd eg3/dev2
docker-compose up --buildYou should see now two devices in the Dashboard:
Problem: turtle is not moving!
Solution: while starting dev1 we didn't new the IPv6 address of the second device, but we know it now.
- Kill
Docker-Composeon the first device (ctrl+c). Add the seconds device address to the Peers list of the first device, by editing:eg3/dev1/cyclonedds.xmlfile:
...
<Discovery>
<Peers>
<Peer address="fc94:406d:ec8a:1e7:6c06:4898:9d68:c6d0"/>
</Peers>
<ParticipantIndex>auto</ParticipantIndex>
</Discovery>
...- Restart the first device container and everything looks fine now:
cd eg3/dev1
docker-compose up --build
It works, but there are a few things that we don't like:
-
we don't know IPv6 addressed of the containers before starting them. So we need to make a dummy start of the first container, just to get the IPv6 address to be written in
cyclonedds.xmlof the second container. -
we need to modify containers that we already have to connect them over the Internet (installing VPN client within a containers)
We will fix those issues in the example number 4.s
Instead of modyfing your own containers, you can launch a separate official Husarnet VPN container next to your existing app container.
hnet0 network interface from Husarnet container is shared with any container you specify in the docker-compose.yml. Thanks to that without modyfying your exisitng container with ROS 2 nodes, you can connect them with remote nodes without any effor.
Moreover instead of long IPv6 addresses you can use Husarnet hostnames of the Husarnet Container (specified in eg4/dev*/.env files).
That's a truely zero effort solution that simply works.
TL;DR:
Clone this repo to the first device, then execute in the terminal:
cd ros2_docker_examples/eg4/dev1
# Add your own join code to the .env file in the current directory.
# Example .env file content:
#
# JOINCODE=fc94:b01d:1803:8dd8:b293:5c7d:7639:932a/tTZtwiqM59iXtnCWABUEKH
# HOSTNAME=turtle-controller-1
docker-compose up --buildClone this repo to the second device, then execute in the terminal:
xhost local:root
cd ros2_docker_examples/eg4/dev2
# Add your own join code to the .env file in the current directory.
# Example .env file content:
#
# JOINCODE=fc94:b01d:1803:8dd8:b293:5c7d:7639:932a/tTZtwiqM59iXtnCWABUEKH
# HOSTNAME=turtlesim-1
docker-compose up --build
Note that we haven't modified cyclonedds.xml file, because we specified there hostnames of Husarnet containers (in .env file) insted of IPv6 address.
OK, pretty nice, but we still needed to create a custom Dockerfile even for just running a turtlesime. Our next goal is to find a way to do not build a special Docker Images "working with Husarnet", but run any existing ROS 2 image, by just applying the proper configuration in the Docker Compose.
cd ros2_docker_examples/eg5/dev1
# Add your own join code to the .env file in the current directory.
# Example .env file content:
#
# JOINCODE=fc94:b01d:1803:8dd8:b293:5c7d:7639:932a/tTZtwiqM59iXtnCWABUEKH
# HOSTNAME=turtle-controller-2
docker-compose up --buildClone this repo to the second device, then execute in the terminal:
xhost local:root
cd ros2_docker_examples/eg5/dev2
# Add your own join code to the .env file in the current directory.
# Example .env file content:
#
# JOINCODE=fc94:b01d:1803:8dd8:b293:5c7d:7639:932a/tTZtwiqM59iXtnCWABUEKH
# HOSTNAME=turtlesim-2
docker-compose up --buildThe same :)
OK, so we can run our system containing 3 containers on two machines. It's completely fine, but to make our system more understabable by only reading a docker-compose.yml, instead of running a single turtle_controller container, we can run all ROS nodes in the separate containers.
cd ros2_docker_examples/eg6/dev1
# Add your own join code to the .env file in the current directory.
# Example .env file content:
#
# JOINCODE=fc94:b01d:1803:8dd8:b293:5c7d:7639:932a/tTZtwiqM59iXtnCWABUEKH
# HOSTNAME=turtle-controller-6
docker-compose up --buildClone this repo to the second device, then execute in the terminal:
xhost local:root
cd ros2_docker_examples/eg6/dev2
# Add your own join code to the .env file in the current directory.
# Example .env file content:
#
# JOINCODE=fc94:b01d:1803:8dd8:b293:5c7d:7639:932a/tTZtwiqM59iXtnCWABUEKH
# HOSTNAME=turtlesim-6
docker-compose up --buildThe same :)
Our network works pretty well, configuration is nice, however if we would like to add 3rd device to the network, we would need to add new Peer's hostname in cyclonedds.xml files of 1st and 2nd device. In the next example we will introduce a separate DDS updater container that will update a Peer's list automatically by using /etc/hosts file being updated by Husarnet VPN.
....TODO
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