Orchestration

Estimated reading time: 9 minutes

The portability and reproducibility of a containerized process provides an opportunity to move and scale our containerized applications across clouds and datacenters. Containers effectively guarantee that those applications run the same way anywhere, allowing us to quickly and easily take advantage of all these environments. Additionally, as we scale our applications up, we need some tooling to help automate the maintenance of those applications, enable the replacement of failed containers automatically, and manage the rollout of updates and reconfigurations of those containers during their lifecycle.

Tools to manage, scale, and maintain containerized applications are called orchestrators, and the most common examples of these are Kubernetes and Docker Swarm. Development environment deployments of both of these orchestrators are provided by Docker Desktop, which we’ll use throughout this guide to create our first orchestrated, containerized application.

The advanced modules teach you how to:

  1. Set up and use a Kubernetes environment on your development machine
  2. Set up and use a Swarm environment on your development machine

Enable Kubernetes

Docker Desktop will set up Kubernetes for you quickly and easily. Follow the setup and validation instructions appropriate for your operating system:

Mac

  1. After installing Docker Desktop, you should see a Docker icon in your menu bar. Click on it, and navigate to Preferences > Kubernetes.

  2. Check the checkbox labeled Enable Kubernetes, and click Apply & Restart. Docker Desktop will automatically set up Kubernetes for you. You’ll know that Kubernetes has been successfully enabled when you see a green light beside ‘Kubernetes running’ in the Preferences menu.

  3. In order to confirm that Kubernetes is up and running, create a text file called pod.yaml with the following content:

    apiVersion: v1
    kind: Pod
    metadata:
      name: demo
    spec:
      containers:
      - name: testpod
        image: alpine:3.5
        command: ["ping", "8.8.8.8"]
    

    This describes a pod with a single container, isolating a simple ping to 8.8.8.8.

  4. In a terminal, navigate to where you created pod.yaml and create your pod:

    kubectl apply -f pod.yaml
    
  5. Check that your pod is up and running:

    kubectl get pods
    

    You should see something like:

    NAME      READY     STATUS    RESTARTS   AGE
    demo      1/1       Running   0          4s
    
  6. Check that you get the logs you’d expect for a ping process:

    kubectl logs demo
    

    You should see the output of a healthy ping process:

    PING 8.8.8.8 (8.8.8.8): 56 data bytes
    64 bytes from 8.8.8.8: seq=0 ttl=37 time=21.393 ms
    64 bytes from 8.8.8.8: seq=1 ttl=37 time=15.320 ms
    64 bytes from 8.8.8.8: seq=2 ttl=37 time=11.111 ms
    ...
    
  7. Finally, tear down your test pod:

    kubectl delete -f pod.yaml
    

Windows

  1. After installing Docker Desktop, you should see a Docker icon in your system tray. Right-click on it, and navigate Settings > Kubernetes.

  2. Check the checkbox labeled Enable Kubernetes, and click Apply & Restart. Docker Desktop will automatically set up Kubernetes for you. You’ll know that Kubernetes has been successfully enabled when you see a green light beside ‘Kubernetes running’ in the Settings menu.

  3. In order to confirm that Kubernetes is up and running, create a text file called pod.yaml with the following content:

    apiVersion: v1
    kind: Pod
    metadata:
      name: demo
    spec:
      containers:
      - name: testpod
        image: alpine:3.5
        command: ["ping", "8.8.8.8"]
    

    This describes a pod with a single container, isolating a simple ping to 8.8.8.8.

  4. In PowerShell, navigate to where you created pod.yaml and create your pod:

    kubectl apply -f pod.yaml
    
  5. Check that your pod is up and running:

    kubectl get pods
    

    You should see something like:

    NAME      READY     STATUS    RESTARTS   AGE
    demo      1/1       Running   0          4s
    
  6. Check that you get the logs you’d expect for a ping process:

    kubectl logs demo
    

    You should see the output of a healthy ping process:

    PING 8.8.8.8 (8.8.8.8): 56 data bytes
    64 bytes from 8.8.8.8: seq=0 ttl=37 time=21.393 ms
    64 bytes from 8.8.8.8: seq=1 ttl=37 time=15.320 ms
    64 bytes from 8.8.8.8: seq=2 ttl=37 time=11.111 ms
    ...
    
  7. Finally, tear down your test pod:

    kubectl delete -f pod.yaml
    

Enable Docker Swarm

Docker Desktop runs primarily on Docker Engine, which has everything you need to run a Swarm built in. Follow the setup and validation instructions appropriate for your operating system:

Mac

  1. Open a terminal, and initialize Docker Swarm mode:

    docker swarm init
    

    If all goes well, you should see a message similar to the following:

    Swarm initialized: current node (tjjggogqpnpj2phbfbz8jd5oq) is now a manager.
    
    To add a worker to this swarm, run the following command:
    
        docker swarm join --token SWMTKN-1-3e0hh0jd5t4yjg209f4g5qpowbsczfahv2dea9a1ay2l8787cf-2h4ly330d0j917ocvzw30j5x9 192.168.65.3:2377
    
    To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
    
  2. Run a simple Docker service that uses an alpine-based filesystem, and isolates a ping to 8.8.8.8:

    docker service create --name demo alpine:3.5 ping 8.8.8.8
    
  3. Check that your service created one running container:

    docker service ps demo
    

    You should see something like:

    ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE           ERROR               PORTS
    463j2s3y4b5o        demo.1              alpine:3.5          docker-desktop      Running             Running 8 seconds ago
    
  4. Check that you get the logs you’d expect for a ping process:

    docker service logs demo
    

    You should see the output of a healthy ping process:

    demo.1.463j2s3y4b5o@docker-desktop    | PING 8.8.8.8 (8.8.8.8): 56 data bytes
    demo.1.463j2s3y4b5o@docker-desktop    | 64 bytes from 8.8.8.8: seq=0 ttl=37 time=13.005 ms
    demo.1.463j2s3y4b5o@docker-desktop    | 64 bytes from 8.8.8.8: seq=1 ttl=37 time=13.847 ms
    demo.1.463j2s3y4b5o@docker-desktop    | 64 bytes from 8.8.8.8: seq=2 ttl=37 time=41.296 ms
    ...
    
  5. Finally, tear down your test service:

    docker service rm demo
    

Windows

  1. Open a powershell, and initialize Docker Swarm mode:

    docker swarm init
    

    If all goes well, you should see a message similar to the following:

    Swarm initialized: current node (tjjggogqpnpj2phbfbz8jd5oq) is now a manager.
    
    To add a worker to this swarm, run the following command:
    
        docker swarm join --token SWMTKN-1-3e0hh0jd5t4yjg209f4g5qpowbsczfahv2dea9a1ay2l8787cf-2h4ly330d0j917ocvzw30j5x9 192.168.65.3:2377
    
    To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
    
  2. Run a simple Docker service that uses an alpine-based filesystem, and isolates a ping to 8.8.8.8:

    docker service create --name demo alpine:3.5 ping 8.8.8.8
    
  3. Check that your service created one running container:

    docker service ps demo
    

    You should see something like:

    ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE           ERROR               PORTS
    463j2s3y4b5o        demo.1              alpine:3.5          docker-desktop      Running             Running 8 seconds ago
    
  4. Check that you get the logs you’d expect for a ping process:

    docker service logs demo
    

    You should see the output of a healthy ping process:

    demo.1.463j2s3y4b5o@docker-desktop    | PING 8.8.8.8 (8.8.8.8): 56 data bytes
    demo.1.463j2s3y4b5o@docker-desktop    | 64 bytes from 8.8.8.8: seq=0 ttl=37 time=13.005 ms
    demo.1.463j2s3y4b5o@docker-desktop    | 64 bytes from 8.8.8.8: seq=1 ttl=37 time=13.847 ms
    demo.1.463j2s3y4b5o@docker-desktop    | 64 bytes from 8.8.8.8: seq=2 ttl=37 time=41.296 ms
    ...
    
  5. Finally, tear down your test service:

    docker service rm demo
    

Conclusion

At this point, you’ve confirmed that you can run simple containerized workloads in Kubernetes and Swarm. The next step will be to write the Kubernetes yaml that describes how to run and manage these containers on Kubernetes.

On to deploying to Kubernetes >>

To learn how to write the stack file to help you run and manage containers on Swarm, see Deploying to Swarm.

CLI references

Further documentation for all CLI commands used in this article are available here:

orchestration, deploy, kubernetes, swarm