6_Scale_up_and_Scale_down_the_application_instances.adoc

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 consoleproject-UserName that you created in the previous lab. Make sure you are switched to that project by using the oc project command and remember to substitute UserName.

$ oc project consoleproject-UserName

Step 2: View the deployment config

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

$ oc get deploymentConfig/pricelist -o yaml

apiVersion: v1
kind: DeploymentConfig
metadata:
  annotations:
    openshift.io/generated-by: OpenShiftWebConsole
  creationTimestamp: 2018-04-09T14:01:00Z
  generation: 4
  labels:
    app: pricelist
  name: pricelist
  namespace: jimgarrett
  resourceVersion: "127826410"
  selfLink: /oapi/v1/namespaces/jimgarrett/deploymentconfigs/pricelist
  uid: 6f1fcd76-3bfe-11e8-888a-02722ccca8d2
spec:
  replicas: 1
  selector:
    deploymentconfig: pricelist
  strategy:
    activeDeadlineSeconds: 21600
    resources: {}
    rollingParams:
      intervalSeconds: 1
      maxSurge: 25%
      maxUnavailable: 25%
      timeoutSeconds: 600
      updatePeriodSeconds: 1
    type: Rolling
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: pricelist
        deploymentconfig: pricelist
    spec:
      containers:
      - env:
        - name: MYSQL_SERVICE_HOST
          value: mysql
        - name: MYSQL_SERVICE_PORT
          value: "3306"
        - name: MYSQL_DATABASE
          value: pricelist
        - name: MYSQL_USER
          value: pricelist
        - name: MYSQL_PASSWORD
          value: pricelist
        image: 172.30.245.248:5000/jimgarrett/pricelist@sha256:9e631afc00da201b73e052d2d8509be350e8d9ec8d32e4a6afe8104d49a6162d
        imagePullPolicy: Always
        name: pricelist
        ports:
        - containerPort: 8080
          protocol: TCP
        - containerPort: 8443
          protocol: TCP
        resources: {}
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      terminationGracePeriodSeconds: 30
  test: false
  triggers:
  - imageChangeParams:
      automatic: true
      containerNames:
      - pricelist
      from:
        kind: ImageStreamTag
        name: pricelist:latest
        namespace: jimgarrett
      lastTriggeredImage: 172.30.245.248:5000/jimgarrett/pricelist@sha256:9e631afc00da201b73e052d2d8509be350e8d9ec8d32e4a6afe8104d49a6162d
    type: ImageChange
  - type: ConfigChange
status:
  availableReplicas: 1
  conditions:
  - lastTransitionTime: 2018-04-09T14:01:34Z
    lastUpdateTime: 2018-04-09T14:01:34Z
    message: Deployment config has minimum availability.
    status: "True"
    type: Available
  - lastTransitionTime: 2018-04-09T14:05:04Z
    lastUpdateTime: 2018-04-09T14:05:05Z
    message: replication controller "pricelist-3" successfully rolled out
    reason: NewReplicationControllerAvailable
    status: "True"
    type: Progressing
  details:
    causes:
    - type: ConfigChange
    message: config change
  latestVersion: 3
  observedGeneration: 4
  readyReplicas: 1
  replicas: 1
  unavailableReplicas: 0
  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
mysql-1-ttvml       1/1       Running     0          57m
pricelist-1-build   0/1       Completed   0          27m
pricelist-3-2b489   1/1       Running     0          23m....

This shows that the build `pricelist-3` is running in pod `2b489`. Let us
view the `rc` on this build.

$ oc get rc/pricelist-3
NAME          DESIRED   CURRENT   READY     AGE
pricelist-3   1         1         1         24m

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.

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

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

If you look at the web console and you will see that there are 3 instances running now

Note: You can also scale up and down from the web console by going to the project overview page and clicking twice on 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
pricelist-1-build   0/1       Completed   0          30m
pricelist-3-2b489   1/1       Running     0          26m
pricelist-3-kq5x8   1/1       Running     0          1m
pricelist-3-mfrmb   1/1       Running     0          1m

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

$ oc get rc/pricelist-3

NAME        DESIRED   CURRENT   AGE
pricelist-3    3         3         3h

Step 4: Idling the application

Run the following command to find the available endpoints

$ oc get endpoints
NAME        ENDPOINTS                                           AGE
pricelist   10.1.10.160:8080,10.1.16.190:8080,10.1.3.105:8080   32m

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

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

$ oc idle endpoints/pricelist
The service "jimgarrett/pricelist" has been marked as idled
The service will unidle DeploymentConfig "jimgarrett/pricelist" to 3 replicas once it receives traffic
DeploymentConfig "jimgarrett/pricelist" has been idled

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

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 pricelist application dc setting.

oc scale --replicas=1 dc/pricelist

deploymentconfig "pricelist" scaled

Alternately, you can go to project overview page and click on 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!

Let’s clean up your project before continuing to the next lab.

$ oc delete project consoleproject-UserName

Next Lab

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