Next Steps for viewers of "Kubernetes Extensibility", presented at Dockercon SF 2018 by Eric Tune and Tim Hockin

README.md

Activating Kubernetes for Docker

Follow Docker's activation Instructions:

• Mac: https://blog.docker.com/2018/01/docker-mac-kubernetes/
• Windows: https://blog.docker.com/2018/01/docker-windows-desktop-now-kubernetes/
• I'm told it works on Docker EE 2.0 too.
• I used Docker for Mac Edge for this demo.

Make sure you can talk to local kubernetes using kubectl before going to next steps. You should see:

$ kubectl config current-context
docker-for-desktop
$ kubectl cluster-info
Kubernetes master is running at https://localhost:6443
...

Deploy a Stack

Get a sample compose file.

$ mkdir stackdemo 
$ curl https://gist.githubusercontent.com/erictune/f025f922726566a3a6045e5ae7997948/raw/3b6a6ef6e192eb0de289c5ac6f1dba851aa653c8/docker-compose.yml > docker-compose.yml
$ kubectl get stacks
No resources found.

$ docker stack deploy --compose-file docker-compose.yml stackdemo

Waiting for the stack to be stable and running...
 - Service web has one container running
 - Service redis has one container running
Stack stackdemo is stable and running

What resources did it make?

$ kubectl get all
NAME           DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deploy/ridis   1         1         1            1           5m

NAME                  DESIRED   CURRENT   READY     AGE
rs/ridis-85d4d69648   1         1         1         5m

NAME                        READY     STATUS    RESTARTS   AGE
po/ridis-85d4d69648-jx94k   1/1       Running   0          5m

NAME                     TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
svc/kubernetes           ClusterIP   10.96.0.1        <none>        443/TCP          29d
svc/ridis                ClusterIP   None             <none>        55555/TCP        5m
svc/ridis-random-ports   NodePort    10.101.242.155   <none>        6379:31248/TCP   5m

Explore How Docker Uses Kubernetes API Extensions

Exploring Stacks API

Let's see if kubectl knows about the stack.

$ kubectl get stacks
NAME        AGE
stackdemo   39s

Yes, it does. How is this magic possible?

Let's use a proxy to trace what kubectl is doing.

# Preferably in another shell
$ kubectl proxy -v 5 &

$ kubectl get stacks -s localhost:8001
...

Now note a line similar to this in the kubectl proxy debug output:

I0613 10:26:38.534101   82905 proxy_server.go:138] Filter accepting GET /apis/compose.docker.com/v1beta2/namespaces/default/stacks localhost

So, there is an API group called compose.docker.com with a resource type stacks. In other words, there is a stacks API on the Kubernetes API Server.

Explore Extension API Servers

How is that possible. Let's explore what APIs are part of that api server.

$ kubectl get apiservices.apiregistration.k8s.io
NAME                                   AGE
v1.                                    29d
v1.apps                                29d
...
v1beta2.compose.docker.com             29d
...

Hmm. There is one called v1beta2.compose.docker.com looks interesting. Let's investigate.

$ kubectl describe apiservices.apiregistration.k8s.io v1beta2.compose.docker.com 
Name:         v1beta2.compose.docker.com
Namespace:    
Labels:       com.docker.deploy-namespace=docker
              com.docker.fry=compose.api
              com.docker.image-tag=v0.3.0-rc4
Annotations:  <none>
API Version:  apiregistration.k8s.io/v1beta1
Kind:         APIService
Metadata:
  Creation Timestamp:  2018-05-15T13:15:35Z
  Resource Version:    410501
  Self Link:           /apis/apiregistration.k8s.io/v1beta1/apiservices/v1beta2.compose.docker.com
  UID:                 0d62fa42-5842-11e8-bb11-025000000001
Spec:
  Ca Bundle:               LS0t...0K
  Group:                   compose.docker.com
  Group Priority Minimum:  1000
  Service:
    Name:            compose-api
    Namespace:       docker
  Version:           v1beta2
  Version Priority:  16
Status:
  Conditions:
    Last Transition Time:  2018-06-01T18:04:30Z
    Message:               all checks passed
    Reason:                Passed
    Status:                True
    Type:                  Available
Events:                    <none>

Looks like this is pointing to a service. Let's check it out. It is in the docker namespace and called compose-api:

$ kubectl get service -n docker compose-api
NAME          TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
compose-api   ClusterIP   10.110.211.86   <none>        443/TCP   28d

This is pointing to a deployment in the cluster, by the way, called compose-api:

$ kubectl get deploy -n docker
NAME          DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
compose       1         1         1            1           28d
compose-api   1         1         1            1           28d

Learn About Kubernetes API Extensibility

Read the Kubernetes Documentation:

• https://kubernetes.io/docs/concepts/extend-kubernetes/extend-cluster/

Webhooks example:

• https://github.com/kelseyhightower/denyenv-validating-admission-webhook

docker-compose.yml

version: "3.3"
services:
  redis:
    image: redis:alpine
    ports:
      - 6379
    networks:
      - frontend
    deploy:
      replicas: 1
networks:
  frontend:

README.md is missing a triple-backquote right before this line:

Explore How Docker Uses Kubernetes API Extensions

Thanks, fixed.