Since RedHat announced the new OpenShift version 4.0 they said it will be a very different experience to install and operate the platform, mostly because of Operators managing the components of the cluster. A few month back RedHat officially released the Operator-SDK and the Operator Hub to create your own operators and to share them.

I did some testing around the Ansible Operator which I wanted to share in this article but before we dig into creating our own operator we need to first install operator-sdk:

# Make sure you are able to use docker commands
sudo groupadd docker
sudo usermod -aG docker centos
ls -l /var/run/docker.sock
sudo chown root:docker /var/run/docker.sock

# Download Go
wget https://dl.google.com/go/go1.10.3.linux-amd64.tar.gz
sudo tar -C /usr/local -xzf go1.10.3.linux-amd64.tar.gz

# Modify bash_profile
vi ~/.bash_profile
export PATH=$PATH:/usr/local/go/bin:$HOME/go
export GOPATH=$HOME/go

# Load bash_profile
source ~/.bash_profile

# Install Go dep
mkdir -p /home/centos/go/bin
curl https://raw.githubusercontent.com/golang/dep/master/install.sh | sh
sudo cp /home/centos/go/bin/dep /usr/local/go/bin/

# Download and install operator framework
mkdir -p $GOPATH/src/github.com/operator-framework
cd $GOPATH/src/github.com/operator-framework
git clone https://github.com/operator-framework/operator-sdk
cd operator-sdk
git checkout master
make dep
make install
sudo cp /home/centos/go/bin/operator-sdk /usr/local/bin/

Let’s start creating our Ansible Operator using the operator-sdk command line which create a blank operator template which we will modify. You can create three different types of operators: Go, Helm or Ansible – check out the operator-sdk repository:

operator-sdk new helloworld-operator --api-version=hello.world.com/v1alpha1 --kind=Helloworld --type=ansible --cluster-scoped
cd ./helloworld-operator/

I am using the Ansible k8s module to create a Hello OpenShift deployment configuration in tasks/main.yml.

---
# tasks file for helloworld

- name: create deployment config
  k8s:
    definition:
      apiVersion: apps.openshift.io/v1
      kind: DeploymentConfig
      metadata:
        name: '{{ meta.name }}'
        labels:
          app: '{{ meta.name }}'
        namespace: '{{ meta.namespace }}'
...

Please have a look at my Github repository openshift-helloworld-operator for more details.

After we have modified the Ansible Role we can start and build operator which will create container we can afterwards push to a container registry like Docker Hub:

$ operator-sdk build berndonline/openshift-helloworld-operator:v0.1
INFO[0000] Building Docker image berndonline/openshift-helloworld-operator:v0.1
Sending build context to Docker daemon   192 kB
Step 1/3 : FROM quay.io/operator-framework/ansible-operator:v0.5.0
Trying to pull repository quay.io/operator-framework/ansible-operator ...
v0.5.0: Pulling from quay.io/operator-framework/ansible-operator
a02a4930cb5d: Already exists
1bdeea372afe: Pull complete
3b057581d180: Pull complete
12618e5abaa7: Pull complete
6f75beb67357: Pull complete
b241f86d9d40: Pull complete
e990bcb94ae6: Pull complete
3cd07ac53955: Pull complete
3fdda52e2c22: Pull complete
0fd51cfb1114: Pull complete
feaebb94b4da: Pull complete
4ff9620dce03: Pull complete
a428b645a85e: Pull complete
5daaf234bbf2: Pull complete
8cbdd2e4d624: Pull complete
fa8517b650e0: Pull complete
a2a83ad7ba5a: Pull complete
d61b9e9050fe: Pull complete
Digest: sha256:9919407a30b24d459e1e4188d05936b52270cafcd53afc7d73c89be02262f8c5
Status: Downloaded newer image for quay.io/operator-framework/ansible-operator:v0.5.0
 ---> 1e857f3522b5
Step 2/3 : COPY roles/ ${HOME}/roles/
 ---> 6e073916723a
Removing intermediate container cb3f89ba1ed6
Step 3/3 : COPY watches.yaml ${HOME}/watches.yaml
 ---> 8f0ee7ba26cb
Removing intermediate container 56ece5b800b2
Successfully built 8f0ee7ba26cb
INFO[0018] Operator build complete.

$ docker push berndonline/openshift-helloworld-operator:v0.1
The push refers to a repository [docker.io/berndonline/openshift-helloworld-operator]
2233d56d407b: Pushed
d60aa100721d: Pushed
a3a57fad5e76: Pushed
ab38e57f8581: Pushed
79b113b67633: Pushed
9cf5b154cadd: Pushed
b191ffbd3c8d: Pushed
5e21ced2d28b: Pushed
cdadb746680d: Pushed
d105c72f21c1: Pushed
1a899839ab25: Pushed
be81e9b31e54: Pushed
63d9d56008cb: Pushed
56a62cb9d96c: Pushed
3f9dc45a1d02: Pushed
dac20332f7b5: Pushed
24f8e5ff1817: Pushed
1bdae1c8263a: Pushed
bc08b53be3d4: Pushed
071d8bd76517: Mounted from openshift/origin-node
v0.1: digest: sha256:50fb222ec47c0d0a7006ff73aba868dfb3369df8b0b16185b606c10b2e30b111 size: 4495

After we have pushed the container to the registry we can continue on OpenShift and create the operator project together with the custom resource definition:

oc new-project helloworld-operator
oc create -f deploy/crds/hello_v1alpha1_helloworld_crd.yaml

Before we apply the resources let’s review and edit operator image configuration to point to our newly create operator container image:

$ cat deploy/operator.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: helloworld-operator
spec:
  replicas: 1
  selector:
    matchLabels:
      name: helloworld-operator
  template:
    metadata:
      labels:
        name: helloworld-operator
    spec:
      serviceAccountName: helloworld-operator
      containers:
        - name: helloworld-operator
          # Replace this with the built image name
          image: berndonline/openshift-helloworld-operator:v0.1
          imagePullPolicy: Always
          env:
            - name: WATCH_NAMESPACE
              value: ""
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
            - name: OPERATOR_NAME
              value: "helloworld-operator"

$ cat deploy/role_binding.yaml
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: helloworld-operator
subjects:
- kind: ServiceAccount
  name: helloworld-operator
  # Replace this with the namespace the operator is deployed in.
  namespace: helloworld-operator
roleRef:
  kind: ClusterRole
  name: helloworld-operator
  apiGroup: rbac.authorization.k8s.io

$ cat deploy/role_user.yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  creationTimestamp: null
  name: helloworld-operator-execute
rules:
- apiGroups:
  - hello.world.com
  resources:
  - '*'
  verbs:
  - '*'

Afterwards we can deploy the required resources:

oc create -f deploy/operator.yaml \
          -f deploy/role_binding.yaml \
          -f deploy/role.yaml \
          -f deploy/service_account.yaml

Create a cluster-role for the custom resource definition and add bind user to a cluster-role to be able to create a custom resource:

oc create -f deploy/role_user.yaml 
oc adm policy add-cluster-role-to-user helloworld-operator-execute berndonline

If you forget to do this you will see the following error message:

Now we can login as your openshift user and create the custom resource in the namespace myproject:

$ oc create -n myproject -f deploy/crds/hello_v1alpha1_helloworld_cr.yaml
helloworld.hello.world.com/hello-openshift created
$ oc describe Helloworld/hello-openshift -n myproject
Name:         hello-openshift
Namespace:    myproject
Labels:       
Annotations:  
API Version:  hello.world.com/v1alpha1
Kind:         Helloworld
Metadata:
  Creation Timestamp:  2019-03-16T15:33:25Z
  Generation:          1
  Resource Version:    19692
  Self Link:           /apis/hello.world.com/v1alpha1/namespaces/myproject/helloworlds/hello-openshift
  UID:                 d6ce75d7-4800-11e9-b6a8-0a238ec78c2a
Spec:
  Size:  1
Status:
  Conditions:
    Last Transition Time:  2019-03-16T15:33:25Z
    Message:               Running reconciliation
    Reason:                Running
    Status:                True
    Type:                  Running
Events:                    

You can also create the custom resource via the web console:

You will get a security warning which you need to confirm to apply the custom resource:

After a few minutes the operator will create the deploymentconfig and will deploy the hello-openshift pod:

$ oc get dc
NAME              REVISION   DESIRED   CURRENT   TRIGGERED BY
hello-openshift   1          1         1         config,image(hello-openshift:latest)

$ oc get pods
NAME                      READY     STATUS    RESTARTS   AGE
hello-openshift-1-pjhm4   1/1       Running   0          2m

We can modify custom resource and change the spec size to three:

$ oc edit Helloworld/hello-openshift
...
spec:
  size: 3
...

$ oc describe Helloworld/hello-openshift
Name:         hello-openshift
Namespace:    myproject
Labels:       
Annotations:  
API Version:  hello.world.com/v1alpha1
Kind:         Helloworld
Metadata:
  Creation Timestamp:  2019-03-16T15:33:25Z
  Generation:          2
  Resource Version:    24902
  Self Link:           /apis/hello.world.com/v1alpha1/namespaces/myproject/helloworlds/hello-openshift
  UID:                 d6ce75d7-4800-11e9-b6a8-0a238ec78c2a
Spec:
  Size:  3
Status:
  Conditions:
    Last Transition Time:  2019-03-16T15:33:25Z
    Message:               Running reconciliation
    Reason:                Running
    Status:                True
    Type:                  Running
Events:                    
~ centos(ocp: myproject) $

The operator will change the deployment config and change the desired state to three pods:

$ oc get dc
NAME              REVISION   DESIRED   CURRENT   TRIGGERED BY
hello-openshift   1          3         3         config,image(hello-openshift:latest)

$ oc get pods
NAME                      READY     STATUS    RESTARTS   AGE
hello-openshift-1-pjhm4   1/1       Running   0          32m
hello-openshift-1-qhqgx   1/1       Running   0          3m
hello-openshift-1-qlb2q   1/1       Running   0          3m

To clean-up and remove the deployment config you need to delete the custom resource

oc delete Helloworld/hello-openshift -n myproject
oc adm policy remove-cluster-role-from-user helloworld-operator-execute berndonline

I hope this is a good and simple example to show how powerful operators are on OpenShift / Kubernetes.