Updating an application

Now that we have deployed our application with Argo CD, let's explore how we can use GitOps principles to update its configuration. In this example, we'll increase the number of replicas for the ui deployment from 1 to 3 using Helm values.

First, we'll create a values.yaml file that configures the number of replicas:

~/environment/eks-workshop/modules/automation/gitops/argocd/update-application/values.yaml
ui:
  replicaCount: 3

Let's copy this configuration file to our Git repository directory:

~$cp ~/environment/eks-workshop/modules/automation/gitops/argocd/update-application/values.yaml \

~/environment/argocd/ui

After adding this file, our Git directory structure should look like this:

~$tree ~/environment/argocd

`-- ui

    |-- Chart.yaml

    `-- values.yaml

Now we'll commit and push our changes to the Git repository:

~$git -C ~/environment/argocd add .

~$git -C ~/environment/argocd commit -am "Update UI service replicas"

~$git -C ~/environment/argocd push

At this point, Argo CD will detect that the application state in the repository has changed. You can either click Refresh and then Sync in the Argo CD UI, or use the argocd CLI to synchronize the application:

~$argocd app sync ui

~$argocd app wait ui --timeout 120

After synchronization completes, the UI deployment should now have 3 pods running:

argocd-update-application

To verify that our update was successful, let's check the deployment and pod status:

~$kubectl get deployment -n ui ui

NAME   READY   UP-TO-DATE   AVAILABLE   AGE

ui     3/3     3            3           3m33s

~$kubectl get pod -n ui

NAME                 READY   STATUS    RESTARTS   AGE

ui-6d5bb7b95-hzmgp   1/1     Running   0          61s

ui-6d5bb7b95-j28ww   1/1     Running   0          61s

ui-6d5bb7b95-rjfxd   1/1     Running   0          3m34s

This demonstrates how GitOps allows us to make configuration changes through version control. By updating our repository and syncing with Argo CD, we've successfully scaled our UI deployment without directly interacting with the Kubernetes API.