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Deploying an application

Objectives

  • Learn abiout the EdgeFarm application model
  • Deploy your first application with kubectl

EdgeFarm application model

Once you have a running EdgeFarm cluster, you can deploy applications to it. To do so, you create a edgefarm.application resource. This resource is a custom resource definition (CRD) that is specific to EdgeFarm. It defines a set of Kubernetes resources that are deployed together as a single unit. The edgefarm.application resource is the primary resource in the EdgeFarm application model, and it represents a single instance of your application. Once you've created an edgefarm.application resource, the Kubernetes control plane schedules the application's Pods to run on your selected nodes.

Writing the manifest

The edgefarm.application resource is a Kubernetes custom resource. You can create it by writing a manifest file that describes the resource. The manifest file is a YAML file that contains the edgefarm.application resource definition. The following example shows a manifest file that creates an edgefarm.application resource. See the edgefarm.application reference for a complete description of the edgefarm.application resource.

Let's create a file called basic.yaml and add the following content: 

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: kubernetes-bootcamp
  namespace: default
spec:
  components:
    - name: kubernetes-bootcamp
      type: edgefarm-applications 
      properties:
        image: gcr.io/google-samples/kubernetes-bootcamp:v1 #(1)!
        nodepoolSelector:
          matchLabels:
            bootcamp: "true" #(2)!

  1. We'll deploy the kubernetes-bootstrap OCI image. This is a simple webserver that will be deployed to the cluster.
  2. We'll deploy to nodepools that have the label bootcamp=true. This label will be added in the next few steps.

Deploying the manifest

To view the Edge Nodes in the cluster, run the kubectl get nodes -l openyurt.io/is-edge-worker=true command.

You see the available edge nodes. Later, we will choose where to deploy our application based on Node available resources.

$ kubectl get nodes -l openyurt.io/is-edge-worker=true
NAME               STATUS   ROLES    AGE    VERSION
edgefarm-worker2   Ready    <none>   9m2s   v1.22.7
edgefarm-worker3   Ready    <none>   9m3s   v1.22.7

$ kubectl get nodepools                 
NAME               TYPE   READYNODES   NOTREADYNODES   AGE
edgefarm-worker2   Edge   1            0               9m5s
edgefarm-worker3   Edge   1            0               9m5s

Note

Every Edge Node is mapped to a corresponding nodepool. This can be seen as a 1:1 relationship. Via labels on the nodepool, we can control which applications are deployed to which node.

Now let's deploy the application and label a nodepool as bootcamp=true.

$ kubectl apply -f basic.yaml #(1)!
application.core.oam.dev/kubernetes-bootcamp created

$ kubectl label nodepools.apps.openyurt.io edgefarm-worker3 bootcamp=true #(2)!
nodepool.apps.openyurt.io/edgefarm-worker3 labeled

$ kubectl get deployments.apps #(3)!
NAME                                         READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp-edgefarm-worker3-8krt7   1/1     1            1           21s

$ kubectl get pods -o wide #(4)!                   
NAME                                                          READY   STATUS    RESTARTS   AGE   IP           NODE              NOMINATED NODE   READINESS GATES
kubernetes-bootcamp-edgefarm-worker3-8krt7-6b4fc49596-56f2h   1/1     Running   0          37s   10.244.2.5   edgefarm-worker3   <none>           <none>
  1. We deploy the application
  2. We label the nodepool edgefarm-worker3 as bootcamp=true
  3. We see that the deployment on node edgefarm-worker3 was successful
  4. We see that the pod is running on node edgefarm-worker3

Testing the application

Now, let's test the application. We'll use the kubectl exec command to run a command in the pod and print its output.

$ kubectl exec -it kubernetes-bootcamp-edgefarm-worker3-8krt7-6b4fc49596-56f2h -- curl http://localhost:8080/version
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-edgefarm-worker3-8krt7-6b4fc49596-56f2h | v=1

Great! The application is running. You've learned how to deploy an application and to control where it will be deployed.