Scaling an application on Tectonic

Kubernetes can scale applications either statically, based on an explicit count of replicas, or dynamically, adding and removing replicas based on application load.

This tutorial outlines static application scaling in Tectonic:

• Scaling an application from 3 replicas up to 5 using kubectl and Tectonic
• Monitoring this change in the Tectonic Console

It is assumed that you have a functioning Tectonic cluster to try these changes.

Scaling a deployment with kubectl

Start by copying the following YAML into a file named cookies.yaml:

apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: cookies
  labels:
    k8s-app: cookies
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 0
      maxSurge: 1
  selector:
    matchLabels:
      k8s-app: cookies
  template:
    metadata:
      labels:
        k8s-app: cookies
    spec:
      containers:
        - name: cookies-container
          image: quay.io/coreos/example-app:v1.0
          ports:
            - name: http
              containerPort: 80
          readinessProbe:
           httpGet:
             path: /
             port: 80
             scheme: HTTP
          livenessProbe:
           initialDelaySeconds: 30
           timeoutSeconds: 1
           httpGet:
             path: /
             port: 80
             scheme: HTTP
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      terminationGracePeriodSeconds: 30

Deploy this file with the following kubectl create command:

$ kubectl create -f cookies.yaml
deployment "cookies" created
$ kubectl get deployments/cookies
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
cookies   3         3         3            3           18s

Next, use the text editor of your choice to change the replicas value to 5:

spec:
  replicas: 5   # bump from 3 to 5

Apply the changes with kubectl apply:

$ kubectl apply -f cookies.yaml
deployment "cookies" configured
$ kubectl get deploy/cookies
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
cookies   5         5         5            5           1m

Notice the pod count increases from 3 to 5.

Scaling a deployment with the kubectl scale subcommand

Deployments can be scaled directly on the kubectl command line with the scale subcommand. The following command scales the cookies Deployment back down to 3 replicas.

$ kubectl scale deployments/cookies --replicas=3
deployment "cookies" scaled
$ kubectl get deployments/cookies
NAME                 DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
cookies              3         3         3            3           6m

Scaling a deployment with Tectonic Console

To control application scale in Tectonic Console, first copy the cookies Deployment's YAML Manifest given above into the Console's YAML editor to create a new deployment:

1. Click Deployments under Workloads.
2. Click the Create Deployment button. The YAML Manifest editor is shown, with a skeletal Manifest file. Delete the example Manifest YAML.
3. Paste the cookies Deployment's Manifest into the editor.
4. Click Create to save and instantiate the cookies Deployment.

Scaling a Deployment with the Console UI

You may also use the Tectonic Console to scale a deployment graphically.

1. Click Workloads > Deployments in the menu at left.
2. Click the Deployment to be scaled. The Deployment detail is shown.
3. Click the current number of pods beneath the Desired Count heading. The Modify Desired Count dialog is shown.
4. Change the number of Replicas with the plus and minus buttons, or by typing the number directly. Click Save Desired Count.

Scaling by editing the Manifest in Tectonic Console

To edit a Deployment's Manifest file in the Console, click Deployments beneath Workloads in the menu at left. Click the Deployment to be edited, named cookies in this example. The Deployment detail is shown. Click the YAML tab. The Deployment Manifest is shown.

Change the replicas count to the desired number of replicas of the Deployment. In this example, the cookies Deployment is scaled from 3 replicas to 5.

spec:
  replicas: 5   # bump from 3 to 5

Click Save Changes to scale the Deployment to the new number of replicas.

Monitoring Deployment scale in Tectonic Console

Use the Pods tab of a given deployment to track the number of Replicas, and the health of those Pods.

NEXT: Versioning and updating an application on Tectonic