12.4. Complex example

In this extended lab, we are going to deploy an existing, more complex application with a Helm chart from the Artifact Hub.

Artifact Hub

Check out Artifact Hub where you’ll find a huge number of different Helm charts. For this lab, we’ll use the WordPress chart by Bitnami , a publishing platform for building blogs and websites.

WordPress

As this WordPress Helm chart is published in Bitnami’s Helm repository, we’re first going to add it to our local repo list:

helm repo add bitnami https://charts.bitnami.com/bitnami

Let’s check if that worked:

helm repo list

NAME    URL
bitnami https://charts.bitnami.com/bitnami

Now look at the available configuration for this Helm chart. Usually you can find it in the values.yaml or in the chart’s readme file. You can also check it on its Artifact Hub page .

We are going to override some of the values. For that purpose, create a new values.yaml file locally on your workstation (e.g. ~/<workspace>/values.yaml) with the following content:

---
persistence:
  size: 1Gi
service:
  type: ClusterIP
updateStrategy:
  type: Recreate

ingress:
  enabled: true
  hostname: wordpress-<namespace>.<appdomain>
  extraTls:
  - hosts:
      - wordpress-<namespace>.<appdomain>


mariadb:
  primary:
    persistence:
      size: 1Gi

If you look inside the Chart.yaml file of the WordPress chart, you’ll see a dependency to the MariaDB Helm chart . All the MariaDB values are used by this dependent Helm chart and the chart is automatically deployed when installing WordPress.

The Chart.yaml file allows us to define dependencies on other charts. In our Wordpress chart we use the Chart.yaml to add a mariadb to store the WordPress data in.

dependencies:
  - condition: mariadb.enabled
    name: mariadb
    repository: https://charts.bitnami.com/bitnami
    version: 9.x.x

Helm’s best practices suggest to use version ranges instead of a fixed version whenever possible. The suggested default therefore is patch-level version match:

version: ~3.5.7

This is e.g. equivalent to >= 3.5.7, < 3.6.0 Check this SemVer readme chapter for more information on version ranges.

Subcharts are an alternative way to define dependencies within a chart: A chart may contain another chart (inside of its charts/ directory) upon which it depends. As a result, when installing the chart, it will install all of its dependencies from the charts/ directory.

We are now going to deploy the application in a specific version (which is not the latest release on purpose). Also note that we define our custom values.yaml file with the -f parameter:

helm install wordpress bitnami/wordpress -f values.yaml --namespace <namespace>

Look for the newly created resources with helm ls and kubectl get deploy,pod,ingress,pvc:

helm ls --namespace <namespace>

which gives you:

NAME      NAMESPACE       REVISION  UPDATED                                     STATUS    CHART             APP VERSION
wordpress <namespace>         1     2021-03-25 14:27:38.231722961 +0100 CET     deployed  wordpress-10.7.1  5.7.0

and

kubectl get deploy,pod,ingress,pvc --namespace <namespace>

which gives you:

NAME                        READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/wordpress   1/1     1            1           2m6s

NAME                             READY   STATUS    RESTARTS   AGE
pod/wordpress-6bf6df9c5d-w4fpx   1/1     Running   0          2m6s
pod/wordpress-mariadb-0          1/1     Running   0          2m6s

NAME                           HOSTS                                          ADDRESS       PORTS   AGE
ingress.extensions/wordpress   wordpress-<namespace>.<appdomain>              10.100.1.10   80      2m6s

NAME                                             STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS            AGE
persistentvolumeclaim/data-wordpress-mariadb-0   Bound    pvc-859fe3b4-b598-4f86-b7ed-a3a183f700fd   1Gi        RWO            cloudscale-volume-ssd   2m6s
persistentvolumeclaim/wordpress                  Bound    pvc-83ebf739-0b0e-45a2-936e-e925141a0d35   1Gi        RWO            cloudscale-volume-ssd   2m7s

In order to check the values used in a given release, execute:

helm get values wordpress --namespace <namespace>

which gives you:

USER-SUPPLIED VALUES:
ingress:
  enabled: true
  hostname: wordpress-<namespace>.<appdomain>
mariadb:
  primary:
    persistence:
      size: 1Gi
persistence:
  size: 1Gi
service:
  type: ClusterIP
updateStrategy:
  type: Recreate

As soon as all deployments are ready (meaning pods wordpress and mariadb are running) you can open the application with the URL from your Ingress resource defined in values.yaml.

Upgrade

We are now going to upgrade the application to a newer Helm chart version. When we installed the Chart, a couple of secrets were needed during this process. In order to do the upgrade of the Chart now, we need to provide those secrets to the upgrade command, to be sure no sensitive data will be overwritten:

• wordpressPassword
• mariadb.auth.rootPassword
• mariadb.auth.password

Use the following commands to gather the secrets and store them in environment variables. Make sure to replace <namespace> with your current value.

export WORDPRESS_PASSWORD=$(kubectl get secret wordpress -o jsonpath="{.data.wordpress-password}" --namespace <namespace> | base64 --decode)

export MARIADB_ROOT_PASSWORD=$(kubectl get secret wordpress-mariadb -o jsonpath="{.data.mariadb-root-password}" --namespace <namespace> | base64 --decode)

export MARIADB_PASSWORD=$(kubectl get secret wordpress-mariadb -o jsonpath="{.data.mariadb-password}" --namespace <namespace> | base64 --decode)

Then do the upgrade with the following command:

helm upgrade -f values.yaml --set wordpressPassword=$WORDPRESS_PASSWORD --set mariadb.auth.rootPassword=$MARIADB_ROOT_PASSWORD --set mariadb.auth.password=$MARIADB_PASSWORD wordpress bitnami/wordpress --namespace <namespace>

And then observe the changes in your WordPress and MariaDB Apps

Cleanup

helm uninstall wordpress --namespace <namespace>

Additional Task

Study the Helm best practices as an optional and additional task.