ros-kubernetes

What • Install • Build • Run • Resources

What

This repository stores a simple kubernetes setup to run the ROS robotic middleware on a distributed cluster. To our knowledge, most of the available tutorials and examples are either outdated or not well documented. Some of them are reported in the Resources section.

This setup is composed of three deployments, each of them running a single-container pod:

• roscore-deployment Runs the roscore process
• talker-deployment Publishes a string message to the /chatter topic
• listener-deployment Subscribes to the /chatter topic and echoes the string

Install

The quicker way to run this kubernetes setup is creating a local cluster with tools such as minikube or kind. Since this is a very trivial setup, we'll be using kind which provides an easy and lightweight cluster. We assume that you already have docker, docker-compose, and kubectl installed, configured, and running in your machine.

Install kind

Refer to the kind repository for the official installation instructions. We'll recap here below the steps we followed:

git clone --depth 1 https://github.com/kubernetes-sigs/kind
cd kind
make build

Then, either add the <path-to-cloned-kind-repo>/bin/ folder to your PATH or add alias kind='<path-to-cloned-kind-repo>/bin/kind' to your ~/.bashrc.

Build the images

All the ROS pods will be running the official ros/melodic-ros-core image. To simplify the kubernetes and kind setup, we extended the official image with minor modifications. You can find the Dockerfiles in the docker folder.

Execute the following commands to build the ROS images:

cd docker
docker-compose -f build-ros-cluster.yml build

After this, make sure with docker images that the following images have been successfully built:

• roscluster/master:v0
• roscluster/node:v0

Run the setup

The first step to run the setup is starting a local cluster. Execute:

kind create cluster
export KUBECONFIG="$(kind get kubeconfig-path)"

Make sure executing docker ps -a that the kindest/node:v1.14.2 container is up and running. Also check that the cluster is running:

$ kubectl get all
NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE                                                          
service/kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   1d17h

Then, load the docker images we built into the local cluster:

kind load docker-image roscluster/master:v0
kind load docker-image roscluster/node:v0

The kubernetes setup is stored in the k8s folder. Execute the following to run the setup:

cd k8s
kubectl create -f .

The three deployments should now start. The talker and listener deployments will likely fail at the first attempt because they need to reach first roscore. Their deployment has an initContainer that tries to connect to roscore and restart the pod if it fails. Furthermore, if during their execution the roscore container fails or is restarted, a livenessProbe will restart the talker and listener containers.

Once that the cluster is running, you should have the following kubectl get all output:

NAME                                      READY   STATUS    RESTARTS   AGE
pod/listener-deployment-c7bfb7856-7lhz2   1/1     Running   1          37s
pod/roscore-deployment-7dd8db86d9-cxb7x   1/1     Running   0          37s
pod/talker-deployment-97cbb7744-b6gdr     1/1     Running   1          37s

NAME                              TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)           AGE
service/kubernetes                ClusterIP      10.96.0.1      <none>        443/TCP           3d17h
service/service-listener          ClusterIP      None           <none>        11311/TCP         37s
service/service-master            ClusterIP      None           <none>        11311/TCP         37s
service/service-talker            ClusterIP      None           <none>        11311/TCP         37s

NAME                                  READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/listener-deployment   1/1     1            1           37s
deployment.apps/roscore-deployment    1/1     1            1           37s
deployment.apps/talker-deployment     1/1     1            1           37s

NAME                                            DESIRED   CURRENT   READY   AGE
replicaset.apps/listener-deployment-c7bfb7856   1         1         1       37s
replicaset.apps/roscore-deployment-7dd8db86d9   1         1         1       37s
replicaset.apps/talker-deployment-97cbb7744     1         1         1       37s

You can get the listener log containing the topic message executing kubectl logs -l node=listener (note that the log is cut using label selectors, use the listener pod name for a complete log).

Resources

• https://blog.zhaw.ch/icclab/challenges-with-running-ros-on-kubernetes/
• https://googlecloudrobotics.github.io/core
• https://rdbox-intec.github.io/homepage_en/