Helm Charts to Rig Capsules

Helm is by now a well established tool for defining your your Kubernetes manifest through a templated abstraction. Most of us can however agree, that Helm Charts quickly become too complex and difficult to maintain. Few developers dare enter the world of Helm templating, and even fewer dare to touch the Helm Chart of another developer. To the rescue comes Rig - With a fixed abstraction layer that standardizes the way developers deploy to, and interact with, Kubernetes, developers can focus on the application logic instead of getting lost in yaml files.

But you have already spent countless hours on you Helm Charts, and you don't want to throw them away? We get that, so we have made it easy to convert your Helm Charts to Rig Capsules, and get you up and running in no time.

In this guide, we will walk through the process of converting the (almost) default nginx helm chart to a Capsule, to be used with Rig. Additionally, we will show you how to deploy the Capsule to your Rig Platform.

The rig-ops CLI, will render the Helm Chart, and base the Capsule on the resulting Kubernetes manifest and perform the migration similar to the approach in the migration section.

Prerequisites

To follow along with this guide, you need to have following:

• rig CLI Installed
• rig-ops CLI installed
• Rig Platform and Operator Running either in KIND or in a real K8s environment

Helm Chart

As stated, the Helm Chart used in this guide is almost the default nginx chart, and contains (mostly) the following files:

values.yaml

# Default values for nginx-chart.
# This is a YAML-formatted file.
# Declare variables to be passed into your templates.

replicaCount: 1

image:
  repository: nginx
  pullPolicy: IfNotPresent
  # Overrides the image tag whose default is the chart appVersion.
  tag: ""

imagePullSecrets: []
nameOverride: ""
fullnameOverride: ""

serviceAccount:
  # Specifies whether a service account should be created
  create: true
  # Annotations to add to the service account
  annotations: {}
  # The name of the service account to use.
  # If not set and create is true, a name is generated using the fullname template
  name: "nginx-chart"

service:
  type: ClusterIP
  port: 80

configMap:
  key: "key"
  value: "Welcome to the nginx chart"

resources: {}
  # We usually recommend not to specify default resources and to leave this as a conscious
  # choice for the user. This also increases chances charts run on environments with little
  # resources, such as Minikube. If you do want to specify resources, uncomment the following
  # lines, adjust them as necessary, and remove the curly braces after 'resources:'.
  # limits:
  #   cpu: 100m
  #   memory: 128Mi
  # requests:
  #   cpu: 100m
  #   memory: 128Mi

autoscaling:
  enabled: true
  minReplicas: 1
  maxReplicas: 100
  targetCPUUtilizationPercentage: 80
  # targetMemoryUtilizationPercentage: 80

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "nginx-chart.fullname" . }}
  labels:
    {{- include "nginx-chart.labels" . | nindent 4 }}
spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.replicaCount }}
  {{- end }}
  selector:
    matchLabels:
      {{- include "nginx-chart.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      labels:
        {{- include "nginx-chart.selectorLabels" . | nindent 8 }}
    spec:
      {{- with .Values.imagePullSecrets }}
      imagePullSecrets:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      serviceAccountName: {{ include "nginx-chart.serviceAccountName" . }}
      volumes:
        - name: config-volume
          configMap:
            name: {{ include "nginx-chart.fullname" . }}
            defaultMode: 420
            items:
              - key: {{ .Values.configMap.key }}
                path: index.html
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - name: http
              containerPort: {{ .Values.service.port }}
              protocol: TCP
          livenessProbe:
            httpGet:
              path: /
              port: http
          readinessProbe:
            httpGet:
              path: /
              port: http
          resources:
            {{- toYaml .Values.resources | nindent 12 }}
          volumeMounts:
            - name: config-volume
              mountPath: /usr/share/nginx/html/index.html
              subPath: index.html

configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ include "nginx-chart.fullname" . }}
  labels:
    {{- include "nginx-chart.labels" . | nindent 4 }}
data:
    {{ .Values.configMap.key }}: {{ .Values.configMap.value }}

hpa.yaml

{{- if .Values.autoscaling.enabled }}
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: {{ include "nginx-chart.fullname" . }}
  labels:
    {{- include "nginx-chart.labels" . | nindent 4 }}
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: {{ include "nginx-chart.fullname" . }}
  minReplicas: {{ .Values.autoscaling.minReplicas }}
  maxReplicas: {{ .Values.autoscaling.maxReplicas }}
  metrics:
    {{- if .Values.autoscaling.targetCPUUtilizationPercentage }}
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: {{ .Values.autoscaling.targetCPUUtilizationPercentage }}
    {{- end }}
    {{- if .Values.autoscaling.targetMemoryUtilizationPercentage }}
    - type: Resource
      resource:
        name: memory
        target:
          type: Utilization
          averageUtilization: {{ .Values.autoscaling.targetMemoryUtilizationPercentage }}
    {{- end }}
{{- end }}

service.yaml

apiVersion: v1
kind: Service
metadata:
  name: {{ include "nginx-chart.fullname" . }}
  labels:
    {{- include "nginx-chart.labels" . | nindent 4 }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: http
      protocol: TCP
      name: http
  selector:
    {{- include "nginx-chart.selectorLabels" . | nindent 4 }}

serviceaccount.yaml

{{- if .Values.serviceAccount.create -}}
apiVersion: v1
kind: ServiceAccount
metadata:
  name: {{ include "nginx-chart.serviceAccountName" . }}
  labels:
    {{- include "nginx-chart.labels" . | nindent 4 }}
  {{- with .Values.serviceAccount.annotations }}
  annotations:
    {{- toYaml . | nindent 4 }}
  {{- end }}
{{- end }}

helpers_.tpl

{{/*
Expand the name of the chart.
*/}}
{{- define "nginx-chart.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{/*
Create a default fully qualified app name.
We truncate at 63 chars because some Kubernetes name fields are limited to this (by the DNS naming spec).
If release name contains chart name it will be used as a full name.
*/}}
{{- define "nginx-chart.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- $name := default .Chart.Name .Values.nameOverride }}
{{- if contains $name .Release.Name }}
{{- .Release.Name | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}
{{- end }}

{{/*
Create chart name and version as used by the chart label.
*/}}
{{- define "nginx-chart.chart" -}}
{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" }}
{{- end }}

{{/*
Common labels
*/}}
{{- define "nginx-chart.labels" -}}
helm.sh/chart: {{ include "nginx-chart.chart" . }}
{{ include "nginx-chart.selectorLabels" . }}
{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

{{/*
Selector labels
*/}}
{{- define "nginx-chart.selectorLabels" -}}
app.kubernetes.io/name: {{ include "nginx-chart.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

{{/*
Create the name of the service account to use
*/}}
{{- define "nginx-chart.serviceAccountName" -}}
{{- if .Values.serviceAccount.create }}
{{- default (include "nginx-chart.fullname" .) .Values.serviceAccount.name }}
{{- else }}
{{- default "default" .Values.serviceAccount.name }}
{{- end }}
{{- end }}

Migration

To migrate the Helm Chart to a Capsule, we will use the migrate command from the rig-ops CLI.

By specifying the Helm Chart directory, the migrate command renders the Helm Chart, and uses the resulting Kubernetes manifest as the base for the Capsule.

rig-ops migrate --helm-dir ./nginx-chart

By default, the the values in the Helm Chart are used, but you can override them by specifying the --values-file flag.

rig-ops migrate --helm-dir ./nginx-chart --values-file ./other-values.yaml

This will go through the flow described in the migration guide, and at the end you will be presented with a Platform Capsule and a diff of the k8s resources.

Capsule

In the end, the resulting Capsule file should look something like this:

nginx-capsule.yaml

apiVersion: platform.rig.dev/v1
environment: prod
kind: Capsule
name: migrate-nginx-chart
project: test
spec:
  files:
  - path: /usr/share/nginx/html/index.html
    string: Welcome to the nginx chart
  image: nginx:1.16.0
  interfaces:
  - liveness:
      path: /
    name: http
    port: 80
    readiness:
      path: /
  scale:
    horizontal:
      cpuTarget:
        utilization: 80
      instances:
        max: 100
        min: 1

Deploying the Capsule

It is either possible to directly deploy the result of the migration command, or to save the Capsule to a file, adjust it, and deploy it later.

rig-ops migrate --helm-dir ./nginx-chart --values-file ./other-values.yaml --apply

rig-ops migrate --helm-dir ./nginx-chart --values-file ./other-values.yaml --export ./nginx-capsule.yaml
rig deploy -f ./nginx-capsule.yaml