Creating Kubernetes resources using odo

While odo is mainly focused on application developers who would like to care less about Kubernetes and more about getting their application running on top of it, it also tries to make things simple for application architects or devfile stack authors who are comfortable with Kubernetes. One such feature of odo that we will discuss in this guide is creation of Kubernetes resources like Pods, Deployments, Services (Kubernetes Services, not the Operator backed ones) and such using odo. Using this, if an advanced user would like to create some Kubernetes resources, they could edit the devfile.yaml and add it there. An odo push after the edit would create the resource on the cluster. A resource thus created would co-exist with an odo component.

In this guide, we will create an nginx Deployment using its Kubernetes manifest. We will write this manifest in the devfile.yaml. Upon doing odo push, you will be able to see a Deployment and its Pods along with the component on the Kubernetes cluster using kubectl commands.

Create an odo component

As with other resources like URL, Storage and Services, to create a Kubernetes resource, we first need to have an odo component. We will keep it simple by using a nodejs starter project. In an empty directory, create a component using:

odo create nodejs --starter nodejs-starter

Example:

$ odo create nodejs --starter nodejs-starter
Devfile Object Validation
 ✓  Checking devfile existence [52416ns]
 ✓  Creating a devfile component from registry: stage [95517ns]
Validation
 ✓  Validating if devfile name is correct [97488ns]

Starter Project
 ✓  Downloading starter project nodejs-starter from https://github.com/odo-devfiles/nodejs-ex.git [593ms]

Please use `odo push` command to create the component with source deployed

Reference the Deployment manifest in devfile.yaml

odo supports referencing a URI in the devfile.yaml so that you don't have to copy the entire manifest into it. Assuming you have a Deployment manifest like below stored in a file called deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
    replicas: 3
    selector:
      matchLabels:
        app: nginx
    template:
      metadata:
        labels:
          app: nginx
      spec:
        containers:
          - name: nginx
            image: quay.io/bitnami/nginx
            ports:
              - containerPort: 80

Add below to the components section in devfile.yaml. Note that there is already a runtime component in this section:

- name: nginx-deploy
  kubernetes:
    uri: deployment.yaml

Push to the cluster

Now you need to do odo push. odo will create the component and also the nginx deployment for you on the cluster. Note that, unlike for Operator backed service, odo won't show you any message indicating that a service or some resource was created on the cluster. This is by design because the feature is meant for advanced users who can play with resources created in this way through kubectl CLI. However, if odo fails to create a resource, it will error out and let you know about it.

See if the Deployment and its Pods were created on the cluster using:

kubectl get deploy
kubectl get pods

Good to know

odo adds a Kubernetes label to the resources created in this way. It is app.kubernetes.io/managed-by: odo. odo also sets the ownerReferences for such objects to the underlying odo component so that when you do odo delete, such resources are deleted from the cluster. Other than that, odo doesn't help in managing such resources and users are expected to know how to do so.