In a GitOps workflow, YAML is king. The premise of GitOps is declarative infrastructure stored as Kubernetes-native manifest on Git, which can be automatically synchronized using a tool like Argo CD. Most of the time manifests are stored as YAML. Teams implementing GitOps methodologies use this “Infrastructure-as-Code” workflow to automatically synchronize the desired state in Git, with the running state in their Kubernetes cluster.
But what if you and your organization are heavily invested in Helm? In this blog, we will explore how you can take advantage of all of what Argo CD has to offer while still using Helm in your GitOps workflows.
Native Helm Support in Argo CD
The most straightforward way to use Helm in your GitOps workflow is to use the native support built in to Argo CD. Let’s take a look at an example Application manifest used to deploy a Helm chart.
- name: build.enabled
- name: deploy.route.tls.enabled
- name: image.name
This Argo CD Application deploys a sample Quarkus application from the Red Hat Developer Helm Repository. Using an Argo CD Application manifest, you can supply parameters directly in the manifest file. You also can provide the repo and the name of the chart you want to deploy.
Note: Argo CD assumes that you’re using Helm v3 (even if the apiVersion field in the chart is Helm v2), unless v2 is explicitly specified in the Argo CD Application manifest. More information can be found in the official documentation.
Once you’ve applied this manifest, you will see it as “progressing” in the Argo CD UI.
After some time the sample application will be in sync. If you click on the Application “card”, it’ll take you to the “tree view” of the application.
Now that the Application is deployed and synced, you can check all the resources the Helm chart created.
$ oc get pod,svc,deploy -n demo
NAME READY STATUS RESTARTS AGE
pod/quarkus-app-58f475cb86-s9fbp 1/1 Running 0 27m
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/quarkus-app ClusterIP 172.30.169.168 <none> 8080/TCP 27m
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/quarkus-app 1/1 1 1 27m
You can interact with your Helm deployment through Argo CD now, via the UI or the CLI. Below is an example of updating one of the values for the Helm Chart. I am setting deploy.replicas to 2 so that I can have two pods for my deployment.
$ argocd app set quarkus-app -p deploy.replicas=2
This will update your Application to now deploy 2 replicas, giving you two Pods.
$ oc get pods -n demo
NAME READY STATUS RESTARTS AGE
quarkus-app-58f475cb86-gjlmx 1/1 Running 0 27m
quarkus-app-58f475cb86-s9fbp 1/1 Running 0 67
Although this way is supported, it does have some drawbacks. First, this breaks the first rule of GitOps. Everything in Git! There is no reflection of the desired state that is stored in the SCM. Another drawback is that there is a 1:1, Chart to Application, mapping when doing it this way. Meaning that if your application stack is made up of multiple Helm charts, you’ll have to create an Argo CD Application for each chart.
Helm Subchart Deployments
Another way to use Argo CD is to use the Helm Subchart deployment pattern. In this method, the actual Helm values are stored in Git. This has the advantage of having your Helm manifests version controlled and deployed declaratively. Let’s take the same Quarkus example and see how this would look like.
A tree of the directory structure where my manifest would be on Git.
$ tree quarkus-subchart/
0 directories, 2 files
As you can see, it’s a pretty simple configuration. Let’s take a look at where the magic happens. Taking a look at the Chart.yaml file, you can see the following configuration.
- name: quarkus
Using this method, you create an “empty” Helm chart (in my case, this empty chart is called quarkus-subchart) and you list out other charts that you have as dependencies. This is why it’s called “Subchart Deployment”. Take note that dependencies is an array. So this has the advantage of being able to specify multiple Helm Charts as one atomic unit.
Taking a look at the values.yaml file, you’ll see where you can specify your parameters. Here you’ll have a section for each Subchart.
Using these two files stored in my Git repository; I can now create my Application manifest.
Notice how this differs from the other manifest. This Application manifest doesn’t include anything about Helm. This is because you’re just syncing the manifests from Git, instead of supplying the values in this file. Applying this manifest, shows this on the Argo CD UI.
Note the icons in the upper left corner. One registers as a “Helm Application” and the other as a “Git Application”, which just means that the values for my Helm chart come from the Git repo. I can verify this by seeing if my quarkus-subchart application deployed 3 replicas (as it was stated in my values.yaml file).
$ oc get pods -n test
NAME READY STATUS RESTARTS AGE
quarkus-subchart-77448bbc98-5sk6j 1/1 Running 0 22m
quarkus-subchart-77448bbc98-6jxsf 1/1 Running 0 22m
quarkus-subchart-77448bbc98-zddlr 1/1 Running 0 22m
To make a change here, I wouldn’t use the argocd CLI or the UI. Since the manifests are stored in Git, you will have to make a PR to the repository and edit the values.yaml file there. Argo CD will then pick up the changes and make sure they are synced to your cluster.
You can read more about Helm Dependency from the GitHub Repo.
Things To Look Out For
One thing to note is that Helm charts deployed by Argo CD do not register as Helm deployments. If you run the helm ls command, you won’t see anything.
$ helm ls --all-namespaces
NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION
Why is this? Quite simply because how Argo CD deploys Helm charts. Argo CD effectively does the equivalent of: helm template . <options> | kubectl apply -f -
This has the side effect of Argo CD loading in “bare” manifests without the Helm payload information going into the namespace secret. To learn more about how Helm handles deployments read the official documentation about the architecture and differences between v2 and v3.
In this blog we went over different ways you can integrate Helm charts in your GitOps workflow. Using Argo CD, you can unify your applications and Helm deployments into one logical atomic unit.
OpenShift GitOps includes Argo CD, Tekton, and other tools to help you create your GitOps workflows, in a Kubernetes-native way, on OpenShift. Read more about OpenShift GitOps on our announcement blog. To learn more about GitOps in general, please make sure to tune in to GitOps Guide to the Galaxy on OpenShift.TV! We stream live every other Thursday at 3pm Eastern Time. You can catch up on past shows by visiting https://red.ht/gitops.
How-tos, OpenShift 4, deployments, Quarkus, ci/cd, Argo CD