Creating an Addon

A Kontena Pharos cluster addon is a folder that contains addon.rb (Ruby DSL) and one or more Kubernetes YAML files in the resources folder. It is possible to use erb templating language if you use .yml.erb as the file extension.

Addon Template Variables

Following variables are always available to resource templates:

• name - addon name
• version - addon version
• license - addon license
• arch - cluster cpu architecture
• config - user defined configuration variables

Validating Addon Configuration

Validation rules can be defined in the config_schema block. Block uses dry-validation as the DSL.

Example

pharos-addons/hello-world/addon.rb:

Pharos.addon 'hello-world' do
  version '1.0.0'
  license 'Apache License 2.0'

  # config schema is optional, it provides validation rules for user configurable options
  config_schema do
    required(:replicas).filled(:int?)
    optional(:virtualhost).filled(:str?)
    optional(:tls_secret).filled(:str?)
  end

  # Install is optional, it can be used to customize the installation process if needed
  #
  # install do
  #   logger.info "this happens before resources are applied to Kubernetes API"
  #   apply_resources
  #   logger.info "this happens after resources are applied to Kubernetes API"
  # end

  # Uninstall is optional, it can be used to customize the uninstall process if needed
  #
  # uninstall do
  #   logger.info "this happens before resources are deleted from Kubernetes API"
  #   delete_resources
  #   logger.info "this happens after resources are deleted from Kubernetes API"
  # end
end

pharos-addons/hello-world/resources/deployment.yml.erb:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: <%= name %>
spec:
  selector:
    name: <%= name %>
  replicas: <%= config.replicas %>
  template:
    metadata:
      labels:
        app: <%= name %>
    spec:
      containers:
        - image: "kontena/hello-world:latest"
          imagePullPolicy: Always
          name: hello-world
          ports:
            - containerPort: 9292
          resources:
            limits:
              cpu: "200m"
              memory: "128Mi"
            requests:
              cpu: "20m"
              memory: "64Mi"

pharos-addons/hello-world/resources/service.yml.erb:

apiVersion: v1
kind: Service
metadata:
  name: <%= name %>
spec:
  ports:
     -  port: 9292
        protocol: TCP
        targetPort: 9292
  selector:
    app: <%= name %>

pharos-addons/hello-world/resources/ingress.yml.erb:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: <%= name %>
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
spec:
<% if config.tls_secret %>
  tls:
  - hosts:
    - "<%= config.virtualhost %>"
    secretName: <%= config.tls_secret %>
<% end %>
  rules:
  - http:
      paths:
      - backend:
          serviceName: hello-world
          servicePort: 9292
    <% if config.virtualhost %>
    host: <%= config.virtualhost %>
    <% end %>

Addon can be configured in cluster.yml with the following syntax:

addons:
  hello-world:
    enabled: true
    replicas: 3
    virtualhost: www.myhellodomain.com