Using Docker CE (Community Edition) with Kubernetes

Note perev. : The author of the article, Melvin Dave Vivas, who leads the team of developers and SRE engineers at a Singapore bank, shares his experience of acquaintance with Kubernetes support in the Docker platform.

When last October at DockerCon 2017, Docker Inc Technical Director Solomon Hykes announced native support for Kubernetes, I was very curious about how this would work.



Therefore, after the announcement, I decided to check the availability of this support in the Edge version, asMichael Frills wrote on the Docker blog. But at that time it was not there. And now, after several months of waiting, she finally appeared.

Kubernetes' experimental support in Docker CE (Community Edition) was introduced in a January update. Release Notes reports that it has appeared since version 17.12.0-ce. I myself use Edge, so I'm not sure if the update is available in the mainstream version either.



In general, seeing such a notification, I installed the update. After installation, however, you still need to enable Kubernetes support in the Preferences:



After activating Kubernetes, I tried to execute the command with kubectl, but connecting to the server returned an error:



“Out of the box” did not work, but the whole thing turned out to be in my specific configuration. As reported in the Docker documentation , if you used Minikube before, you need to switch context. To do this, run the command:

$ kubectl config use-context docker-for-desktop

After that, everything works - errors about the timeout are gone:



Time to go to the interesting part. As promised, the teams dockershould work with Kubernetes in Docker. Create a new deployment based on the Compose file for docker stack. I used demo-docker-kube-stack.ymlwhich can be picked up from this repository :

version: "3.3"
services:
  ms1:
    image: melvindave/spring-boot-example
    ports: 
      - "8080:8080"
    networks:
      - backend
    deploy:
      replicas: 3
  nginx:
    image: nginx
    ports:
      - "80:80"
    networks:
      - frontend      
    deploy:
      replicas: 1 
networks:
  backend:   

Stack deployment in Kubernetes cluster:

$ docker stack deploy --namespace docker-kube-demo --compose-file demo-docker-kube-stack.yml demo-docker-kube-stack

Wait a few seconds and you will see that the services have started. Services in Kubernetes are similar to Services in Swarm, and hearths are like containers.



More information about each service can be obtained using this command:

$ kubectl describe services 

You can check the containers with docker ps. The conclusion should be equivalent kubectl get pods:



To be able to access the service from the host, which in my case was a Mac computer, you need to open the service using the type NodePort:

$ kubectl expose deployment ms1 --type=NodePort --name=ms1-service
$ kubectl expose deployment nginx --type=NodePort --name=nginx-service

After executing these commands, both services become available from the browser:



Great! Our Stack is running in a Kubernetes cluster.

Running another Stack at the same time in Swarm

By incorporating Kubernetes into Docker CE, this system will become the default orchestrator instead of Swarm. If you want to use Swarm simultaneously with Kubernetes, you must set the environment variable to a DOCKER_ORCHESTRATORvalue swarm.

We will slam the same Stack in Swarm:

$ DOCKER_ORCHESTRATOR=swarm docker stack deploy --compose-file demo-docker-kube-stack.yml demo-docker-swarm-stack

After a few seconds, the services will start:



Note that if you want to check Services / Stacks in Swarm, always (before each command) you need to determine the value of the environment variable DOCKER_ORCHESTRATOR. If you do not change it, then Kubernetes will act as the orchestra:



This docker pswill display a list of all containers, whether they are in Kubernetes or in Swarm:

Kubernetes Dashboard

Since Kubernetes works for us, let's install its dashboard. To do this, just run two commands:

$ kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/master/src/deploy/recommended/kubernetes-dashboard.yaml
$ kubectl proxy

After that, it will be available in the browser at http: // localhost: 8001 / api / v1 / namespaces / kube-system / services / https: kubernetes-dashboard: / proxy / #! / Overview? Namespace = default .

General view:



View View Deployments, Pods, ReplicaSets, Services:



View hearth logs:

PS from the translator

Read also in our blog:

• “ What and why is Docker doing Moby to integrate with Kubernetes?” "
• “ CRI-O is an alternative to Docker for running containers on Kubernetes .”
• « Kubernetes 1.9: overview of the major innovations ."
• “ Infrastructure with Kubernetes as an affordable service .”
• " Overview of GUI Interfaces for Managing Docker Containers ."
• " Cheat Sheet with Docker Commands ."