Package the Application#

Helm uses a packaging format called charts. A chart is a collection of files that describe a related set of Kubernetes resources. A single chart might be used to deploy something simple, like a memcached pod, or something complex, like a full web app stack with HTTP servers, databases, caches, and so on. We need to package the deployments for our application into a Helm Chart.

We need to decide what Kubernetes resources are required for our application. A workload resource (deployment, statefulset) coupled with service and service account resource can be a good starting point.

Objectives#

Package your application for deployment on Stakater App Agility Platform (SAAP) into Helm Chart.

Key Results#

Create helm chart in deploy/ folder.
Explore generic Application helm chart.

Tutorial#

Create a Helm Chart with Application Chart#

1. Create "deploy" directory#

Create a directory named deploy/ in your repository that will contain the helm chart which will be deployed for our application.

mkdir deploy

2. Create `Chart.yaml`#

Create A YAML file containing information about the chart called Chart.yaml.

touch Chart.yaml

apiVersion: v2
name: CHART_NAME
version: 1.0.0
dependencies: # A list of the chart requirements (optional)
  - name: application
    version: 2.1.13
    repository: https://stakater.github.io/stakater-charts
appVersion: "0.0.0"

This dependency chart allows you to define resources without getting overwhelmed by the complexities of different resource with a simple interface. For a full list of configuration visit the chart repository here

3. Create `values.yaml`#

Next create a values.yaml file for default configuration values for this chart. Lets start by defining values for deployment and service.

touch values.yaml

  application:
    applicationName: APP_NAME
    deployment:
      repository: NEXUS_DOCKER_REG_URL
      tag: 1.0.0
    rbac:
      serviceAccount:
        enabled: true

4. Rebuild the charts#

Run helm dependency build to rebuild or update the charts/ directory based on the Chart.lock file.

helm dependency build

5. View the generated resources#

Run helm template . to view the resources generated.

helm template .

This chart will generate deployment, service account and service custom resources. This will highlight any other errors in the chart as well.

  # Source: CHART_NAME/charts/application/templates/serviceaccount.yaml
  apiVersion: v1
  kind: ServiceAccount
  metadata:
    name: APP_NAME
    namespace: default
    labels:
      helm.sh/chart: application-2.1.13
      app.kubernetes.io/managed-by: Helm
      app.kubernetes.io/part-of: APP_NAME
    annotations:
  ---
  # Source: CHART_NAME/charts/application/templates/service.yaml
  apiVersion: v1
  kind: Service
  metadata:
    name: APP_NAME
    namespace: default
    labels:
      helm.sh/chart: application-2.1.13
      app.kubernetes.io/managed-by: Helm
      app.kubernetes.io/part-of: APP_NAME
  spec:  
    type: "ClusterIP"
    selector:
      app.kubernetes.io/name: APP_NAME
    ports:
      - name: http
        port: 8080
        protocol: TCP
        targetPort: 8080
  ---
  # Source: CHART_NAME/charts/application/templates/deployment.yaml
  apiVersion: apps/v1
  kind: Deployment
  metadata:
    labels:
      helm.sh/chart: application-2.1.13
      app.kubernetes.io/managed-by: Helm
      app.kubernetes.io/part-of: APP_NAME
    annotations: 
      reloader.stakater.com/auto: "true"
    name: APP_NAME
    namespace: default
  spec:
    selector:
      matchLabels:
        app.kubernetes.io/name: APP_NAME
    strategy:
      type: RollingUpdate
    template:
      metadata:
        labels:
          app.kubernetes.io/name: APP_NAME
      spec:
        containers:
        - name: APP_NAME
          image: repository/image-name
          imagePullPolicy: IfNotPresent
          resources:
            limits:
              memory: 256Mi
              cpu: 0.5
            requests:
              memory: 128Mi
              cpu: 0.1
          securityContext:
            readOnlyRootFilesystem: true
            runAsNonRoot: true
        serviceAccountName: APP_NAME

If you want to add resources that cannot be defined with dependency chart. You can simply add them in the templates/ folder.

Visit Stakater Nordmart Review Web and Stakater Nordmart Review API to see an example.

Package Stakater Nordmart Review#

Consider the stakater-nordmart-review-api application that we containerized earlier.

1. Clone the repository#

git clone https://github.com/stakater-lab/stakater-nordmart-review-api
cd stakter-nordmart-review-api

2. go to deploy/ directory#

cd deploy

In deploy/ directory you will see the Chart.yaml, values.yaml file and a templates directory.

3. Rebuild/update the charts#

In deploy/ directory run helm dependency build.

helm dependency build

You will see the charts directory and a Chart.lock file has created.

4. View the generated resources#