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6-Scale-up-and-Scale-down-the-application-instances.adoc

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Scale up and Scale down and Idle the application instances

In this exercise we will learn how to scale our application. OpenShift has the capability to scale your application and make sure that many instances are always running.

Step 1: Switch to an existing project

For this exercise, we will be using an already running application. We will be using the mycliproject-UserName that you created in the previous labs. Make sure you are switched to that project by using the oc project command and remember to substitute UserName.

$ oc project mycliproject-UserName

Step 2: View the deployment config

Take a look at the deploymentConfig (or dc) of the time application

$ oc get deploymentConfig/time -o yaml

apiVersion: v1
kind: DeploymentConfig
metadata:
  annotations:
    openshift.io/generated-by: OpenShiftNewApp
  creationTimestamp: 2016-10-06T05:47:52Z
  generation: 2
  labels:
    app: time
  name: time
  namespace: mycliproject-admin
  resourceVersion: "32084"
  selfLink: /oapi/v1/namespaces/mycliproject-admin/deploymentconfigs/time
  uid: 6bb299e0-8b88-11e6-ba5b-080027782cf7
spec:
  replicas: 1
  selector:
    app: time
    deploymentconfig: time
  strategy:
    resources: {}
    rollingParams:
      intervalSeconds: 1
      maxSurge: 25%
      maxUnavailable: 25%
      timeoutSeconds: 600
      updatePeriodSeconds: 1
    type: Rolling
  template:
    metadata:
      annotations:
        openshift.io/container.time.image.entrypoint: '["sh"]'
        openshift.io/generated-by: OpenShiftNewApp
      creationTimestamp: null
      labels:
        app: time
        deploymentconfig: time
    spec:
      containers:
      - image: 172.30.89.28:5000/mycliproject-admin/time@sha256:c490ea632c5362be3a3985285c623e674e58b876e70d9e3f94a151785b2ee87c
        imagePullPolicy: Always
        name: time
        ports:
        - containerPort: 8080
          protocol: TCP
        resources: {}
        terminationMessagePath: /dev/termination-log
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      securityContext: {}
      terminationGracePeriodSeconds: 30
  test: false
  triggers:
  - type: ConfigChange
  - imageChangeParams:
      automatic: true
      containerNames:
      - time
      from:
        kind: ImageStreamTag
        name: time:latest
        namespace: mycliproject-admin
      lastTriggeredImage: 172.30.89.28:5000/mycliproject-admin/time@sha256:c490ea632c5362be3a3985285c623e674e58b876e70d9e3f94a151785b2ee87c
    type: ImageChange
status:
  availableReplicas: 1
  details:
    causes:
    - imageTrigger:
        from:
          kind: ImageStreamTag
          name: time:latest
          namespace: mycliproject-admin
      type: ImageChange
    message: caused by an image change
  latestVersion: 1
  observedGeneration: 2
  replicas: 1
  updatedReplicas: 1

Note that the replicas: is set to 1. This tells OpenShift that when this application deploys, make sure that there is 1 instance.

The replicationController mirrors this configuration initially; the replicationController (or rc) will ensure that there is always the set number of instances always running.

To view the rc for your application first get the current pod running.

oc get pods

NAME           READY     STATUS      RESTARTS   AGE
time-1-45jtc   1/1       Running     0          2h
time-1-build   0/1       Completed   0          2h

This shows that the build time-1 is running in pod 45jtc. Let us view the rc on this build.

$ oc get rc/time-1

NAME      DESIRED   CURRENT   AGE
time-1    1         1         2h

Note: You can change the number of replicas in DeploymentConfig or the ReplicationController.

However note that if you change the deploymentConfig it applies to your application. This means, even if you delete the current replication controller, the new one that gets created will be assigned the REPLICAS value based on what is set for DC. If you change it on the Replication Controller, the application will scale up. But if you happen to delete the current replication controller for some reason, you will loose that setting.

Step 3: Scale Application

To scale your application we will edit the deploymentConfig to 3.

Open your browser to the Overview page and note you only have one instance running.

image

Now scale your application using the oc scale command (remembering to specify the dc)

$ oc scale --replicas=3 dc/time
deploymentconfig "time" scaled

If you look at the web console and you will see that there are 3 instances running now image::images/scale_updown_overview_scaled.png[image]

Note: You can also scale up and down from the web console by going to the project overview page and clicking twice on image::scale_up.jpg[image] right next to the pod count circle to add 2 more pods.

On the command line, see how many pods you are running now:

$ oc get pods

NAME           READY     STATUS      RESTARTS   AGE
time-1-33wyq   1/1       Running     0          10m
time-1-45jtc   1/1       Running     0          2h
time-1-5ekuk   1/1       Running     0          10m
time-1-build   0/1       Completed   0          2h

You now have 3 instances of time-1 running (each with a different pod-id). If you check the rc of the time-1 build you will see that it has been updated by the dc.

$ oc get rc/time-1

NAME      DESIRED   CURRENT   AGE
time-1    3         3         3h

Step 4: Idling the application

Run the following command to find the available endpoints

$ oc get endpoints
NAME      ENDPOINTS                                            AGE
time      10.128.0.33:8080,10.129.0.30:8080,10.129.2.27:8080   15m

Note that the name of the endpoints is time and there are three ips addresses for the three pods.

Run the oc idle endpoints/time command to idle the application

$ oc idle endpoints/time
Marked service mycliproject-veer/time to unidle resource DeploymentConfig mycliproject-veer/time (unidle to 3 replicas)
Idled DeploymentConfig mycliproject-veer/time (dry run)

Go back to the webconsole. You will notice that the pods show up as idled.

image

At this point the application is idled, the pods are not running and no resources are being used by the application. This doesn’t mean that the application is deleted. The current state is just saved.. that’s all.

Step 6: Reactivate your application Now click on the application route URL or access the application via curl.

Note that it takes a little while for the application to respond. This is because pods are spinning up again. You can notice that in the web console.

In a little while the output comes up and your application would be up with 3 pods.

So, as soon as the user accesses the application, it comes up!!!

Step 7: Scaling Down

Scaling down is the same procedure as scaling up. Use the oc scale command on the time application dc setting.

oc scale --replicas=1 dc/time

deploymentconfig "time" scaled

Alternately, you can go to project overview page and click on image::scale_down.jpg[image] twice to remove 2 running pods.

Congratulations!! In this exercise you have learned about scaling and how to scale up/down your application on OpenShift!