Getting started with Kompose

kompose is a tool to help users, familiar with docker-compose, move to Kubernetes. It takes a Docker Compose file and translates it into Kubernetes resources.

kompose is a convenience tool to go from local Docker development to managing your application with Kubernetes. We don’t assume that the transformation from docker compose format to Kubernetes API objects will be perfect, but it helps tremendously to start Kubernetizing your application.

In this example we will create OpenShift artifacts for guestbook app from the docker-compose file using kompose.

Creating OpenShift artifacts.

This step will create the service.json, deploymentconfig.json and imagestream.json files for OpenShift.

$ kompose --provider=openshift convert
INFO[0000] file "frontend-service.json" created
INFO[0000] file "redis-master-service.json" created
INFO[0000] file "redis-slave-service.json" created
INFO[0000] file "frontend-deploymentconfig.json" created
INFO[0000] file "frontend-imagestream.json" created
INFO[0000] file "redis-master-deploymentconfig.json" created
INFO[0000] file "redis-master-imagestream.json" created
INFO[0000] file "redis-slave-deploymentconfig.json" created
INFO[0000] file "redis-slave-imagestream.json" created

Once generated, you can inspect the files and edit these files if you want to make some adddional changes as per your requirement.

{
  "kind": "DeploymentConfig",
  "apiVersion": "v1",
  "metadata": {
    "name": "redis-master",
    "creationTimestamp": null,
    "labels": {
      "service": "redis-master"
    }
  },
  "spec": {
    "strategy": {
      "resources": {}
    },
    "triggers": [
      {
        "type": "ConfigChange"
      },
      {
        "type": "ImageChange",
        "imageChangeParams": {
          "automatic": true,
          "containerNames": [
            "redis-master"
          ],
          "from": {
            "kind": "ImageStreamTag",
            "name": "redis-master:e2e"
          }
        }
      }
    ],
    "replicas": 1,
    "test": false,
    "selector": {
      "service": "redis-master"
    },
    "template": {
      "metadata": {
        "creationTimestamp": null,
        "labels": {
          "service": "redis-master"
        }
      },
      "spec": {
        "containers": [
          {
            "name": "redis-master",
            "image": " ",
            "ports": [
              {
                "containerPort": 6379,
                "protocol": "TCP"
              }
            ],
            "resources": {}
          }
        ],
        "restartPolicy": "Always"
      }
    }
  },
  "status": {}
}

If you prefer YAML files instead of JSON, you can do that using the -y option like so :

$ kompose --provider=openshift convert -y
INFO[0000] file "redis-slave-service.yaml" created
INFO[0000] file "frontend-service.yaml" created
INFO[0000] file "redis-master-service.yaml" created
INFO[0000] file "redis-slave-deploymentconfig.yaml" created
INFO[0000] file "redis-slave-imagestream.yaml" created
INFO[0000] file "frontend-deploymentconfig.yaml" created
INFO[0000] file "frontend-imagestream.yaml" created
INFO[0000] file "redis-master-deploymentconfig.yaml" created
INFO[0000] file "redis-master-imagestream.yaml" created

You can inspect the file and make some additional changes, if required.

apiVersion: v1
kind: DeploymentConfig
metadata:
  creationTimestamp: null
  labels:
    service: redis-slave
  name: redis-slave
spec:
  replicas: 1
  selector:
    service: redis-slave
  strategy:
    resources: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        service: redis-slave
    spec:
      containers:
      - env:
        - name: GET_HOSTS_FROM
          value: dns
        image: ' '
        name: redis-slave
        ports:
        - containerPort: 6379
          protocol: TCP
        resources: {}
      restartPolicy: Always
  test: false
  triggers:
  - type: ConfigChange
  - imageChangeParams:
      automatic: true
      containerNames:
      - redis-slave
      from:
        kind: ImageStreamTag
        name: redis-slave:v1
    type: ImageChange
status: {}

Deploy your application on OpenShift

There are two ways in which you can deploy the application on OpenShift.

1) Using OpenShift cli

$ oc create -f <path/to/artifacts>

Parse a configuration file and create one or more OpenShift objects based on the file contents.

deploymentconfig "frontend" created
imagestream "frontend" created
service "frontend" created
deploymentconfig "redis-master" created
imagestream "redis-master" created
service "redis-master" created
deploymentconfig "redis-slave" created
imagestream "redis-slave" created
service "redis-slave" created

View the Services and Deploymentconfig on OpenShift

$ oc get svc

NAME           CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
frontend       172.30.99.116   <none>        80/TCP     2m
redis-master   172.30.94.229   <none>        6379/TCP   2m
redis-slave    172.30.43.20    <none>        6379/TCP   2m

$ oc get dc

NAME           REVISION   REPLICAS   TRIGGERED BY
frontend       1          1          config,image(frontend:v4)
redis-master   1          1          config,image(redis-master:e2e)
redis-slave    0          1          config,image(redis-slave:v1)

Next, take a look at the pods created by the deployments

$ oc get pods

NAME                   READY     STATUS    RESTARTS   AGE
frontend-1-ojsux       1/1       Running   0          4m
redis-master-1-1ep72   1/1       Running   0          4m

Verify the application

$ curl <frontend-ip>:80

<html ng-app="redis">
  <head>
    <title>Guestbook</title>
    <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.12/angular.min.js"></script>
    <script src="controllers.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/angular-ui-bootstrap/0.13.0/ui-bootstrap-tpls.js"></script>
  </head>
  <body ng-controller="RedisCtrl">
    <div style="width: 50%; margin-left: 20px">
      <h2>Guestbook</h2>
    <form>
    <fieldset>
    <input ng-model="msg" placeholder="Messages" class="form-control" type="text" name="input"><br>
    <button type="button" class="btn btn-primary" ng-click="controller.onRedis()">Submit</button>
    </fieldset>
    </form>
    <div>
      <div ng-repeat="msg in messages track by $index">
        {{msg}}
      </div>
    </div>
    </div>
  </body>
</html>

That’s it! Your application has been deployed on OpenShift in just 2 simple steps.

Note: We can create route, that will expose the frontend service. But this has to be done manually by running oc expose frontend because kompose doesn’t support that yet.

Asciinema for the above steps.

2) Using kompose cli

There is one more way to deploy your aplication directly on OpenShift if you do not want to inspect the artifacts created by kompose. Hence you can completely skip step 1 mentioned in the previous method mentioned above

$ kompose --provider openshift up

This will crate the OpenShift artifacts and deploy it at the same time.

We are going to create OpenShift DeploymentConfigs and Services for your Dockerized application.
If you need different kind of resources, use the 'kompose convert' and 'oc create -f' commands instead.

INFO[0000] Successfully created service: frontend
INFO[0000] Successfully created service: redis-master
INFO[0000] Successfully created service: redis-slave
INFO[0000] Successfully created deployment: frontend
INFO[0000] Successfully created ImageStream: frontend
INFO[0000] Successfully created deployment: redis-master
INFO[0000] Successfully created ImageStream: redis-master
INFO[0000] Successfully created deployment: redis-slave
INFO[0000] Successfully created ImageStream: redis-slave

Your application has been deployed to OpenShift. You can run 'oc get dc,svc,is' for details.

View the Services, Deploymentconfig, ImageStream and Pods created on OpenShift

$ oc get svc

NAME           CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
frontend       172.30.152.108   <none>        80/TCP     3m
redis-master   172.30.31.110    <none>        6379/TCP   3m
redis-slave    172.30.220.107   <none>        6379/TCP   3m

$ oc get dc

NAME           REVISION   REPLICAS   TRIGGERED BY
frontend       1          1          config,image(frontend:v4)
redis-master   1          1          config,image(redis-master:e2e)
redis-slave    0          1          config,image(redis-slave:v1)

$ oc get is

NAME           DOCKER REPO                                 TAGS      UPDATED
frontend       172.30.78.228:5000/guestbook/frontend       v4        5 minutes ago
redis-master   172.30.78.228:5000/guestbook/redis-master   e2e       5 minutes ago
redis-slave    172.30.78.228:5000/guestbook/redis-slave    v1

$ oc get pods

NAME                   READY     STATUS    RESTARTS   AGE
frontend-1-3dx8l       1/1       Running   0          3m
redis-master-1-skbbu   1/1       Running   0          3m

Verify the application

$ curl <frontend-ip>:80

<html ng-app="redis">
  <head>
    <title>Guestbook</title>
    <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.12/angular.min.js"></script>
    <script src="controllers.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/angular-ui-bootstrap/0.13.0/ui-bootstrap-tpls.js"></script>
  </head>
  <body ng-controller="RedisCtrl">
    <div style="width: 50%; margin-left: 20px">
      <h2>Guestbook</h2>
    <form>
    <fieldset>
    <input ng-model="msg" placeholder="Messages" class="form-control" type="text" name="input"><br>
    <button type="button" class="btn btn-primary" ng-click="controller.onRedis()">Submit</button>
    </fieldset>
    </form>
    <div>
      <div ng-repeat="msg in messages track by $index">
        {{msg}}
      </div>
    </div>
    </div>
  </body>
</html>

Your application has been deployed on OpenShift using one single command.

Note: We can create route, that will expose the frontend service. But this has to be done manually by running oc expose frontend because kompose doesn’t support that yet.

Asciinema of the above steps.

kompose can do more. Feel free to explore it here.

kompose --help to find out more options.

Use kompose convert --help to find more about the convert sub command.

Creating OpenShift artifacts.

Deploy your application on OpenShift

1) Using OpenShift cli

View the Services and Deploymentconfig on OpenShift

Next, take a look at the pods created by the deployments

Verify the application

2) Using kompose cli

View the Services, Deploymentconfig, ImageStream and Pods created on OpenShift

Verify the application

More