Deploy Cloud Native Apps on AKS – Happy Helming

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Introduction

Helm is the package manager for the applications built for Kubernetes. Helm helps to manage complex Kubernetes applications with minimal effort. Helm packages are bundled as Charts which are easy to Create, Manage, Deploy and Rollback onto K8s clusters.

What this article covers

An overview of Helm chart and its components
An insight into the Architecture of Helm
A deep look at how Helm chart can be used to deploy Containerised applications onto K8s clusters
Anatomy of Helm chart templates and configurations
Some hands-on examples
A quick showcase of how Helm can work with Azure DevOps to automate application deployment

Components

Chart.yaml

Contains information about the chart
Modify Description
Modify Chart Version
Modify App Version

apiVersion: v2
name: ratingsapi-chart
description: A Helm chart for Ratings API

# A chart can be either an 'application' or a 'library' chart.
#
# Application charts are a collection of templates that can be packaged into versioned archives
# to be deployed.
#
# Library charts provide useful utilities or functions for the chart developer. They're included as
# a dependency of application charts to inject those utilities and functions into the rendering
# pipeline. Library charts do not define any templates and therefore cannot be deployed.
type: application

# This is the chart version. This version number should be incremented each time you make changes
# to the chart and its templates, including the app version.
# Versions are expected to follow Semantic Versioning (https://semver.org/)
version: 0.0.1

# This is the version number of the application being deployed. This version number should be
# incremented each time you make changes to the application. Versions are not expected to
# follow Semantic Versioning. They should reflect the version the application is using.
appVersion: 1.0.0

values.yaml

Configuration values for the chart

deployment:
  name: ratingsapi-deploy
  namespace: aks-workshop-dev
  labels:
    app: ratingsapi-deploy
  selectorLabels:
    app: ratingsapi-pod    
  replicas: 2
  strategyType: RollingUpdate
  maxSurge: 1
  maxUnavailable: 1
  nodeSelector:
    agentpool: aksapipool
  containers:
  - name: ratingsapi-app
    image: <acr_name>/<image_name>:<tag>
    imagePullPolicy: IfNotPresent
    readinessPort: 3000
    readinessPath: /healthz
    livenessPort: 3000
    livenessPath: /healthz
    memoryRequest: "64Mi"
    cpuRequest: "100m"
    memoryLimit: "256Mi"
    cpuLimit: "200m"
    containerPorts: [3000]    
    env:          
    - name: MONGODB_URI
      valueKey: MONGOCONNECTION
      valueSecret: aks-workshop-mongo-secret
service:
  name: ratingsapi-service
  namespace: aks-workshop-dev
  selector:
    app: ratingsapi-pod
  type: ClusterIP
  ports:
  - protocol: TCP
    port: 80
    targetPort: 3000

Chart Templates

Contains multiple Chart templates
All templates are deployed at once
Each Template contains the definition of a K8s object
- Same format as original Deployment YAML file
- Values are replaced by templated values
- Filled up by corresponding values from Values YAML file at runtime

Let us Get into some Action

Create Helm Chart

helm create <chart-name>

Folder Structure

templates
- Contains multiple template yamls
.helmignore
- File containing entries that should NOT be included in the helm package
values-xxx.yaml
- Configuration values for the chart

Configure Chart Release
- Chart.yaml
  - Contains information about the chart
  - Modify Description
  - Modify Chart Version
  - Modify App Version

Define a Chart Template

Conditions

Check existence of an item in yaml

{{ if $ingress.annotations.rewriteTarget }}
    nginx.ingress.kubernetes.io/rewrite-target: {{ $ingress.annotations.rewriteTarget }}
{{ end }}

Loops

Repetitive entries in yaml

{{- range $host := $ingress.hosts }}
  - host: {{ $host.name}}
    http:
      paths:
      {{- range $path := $host.paths }}
      - path: {{ $path.path }}
        pathType: {{ $path.pathType }}
        backend:
          service:
            name: {{ $path.service }}
            port:
              number: {{ $path.port }}
      {{- end }}
{{- end }}

range denotes the start of the Loop block
{{- end }} denotes the end of the Loop block

Assign items in the Loop block in a variable

$host := $ingress.hosts
......
$path := $host.paths

Assign Single Key/Value pair
- Single Value assignments are straight forward
```
pathType: {{ $path.pathType }}
```

Assign Multiple Key/Value pairs

Multiple Value assignments are performed using toYaml keyword

Indentation is for successful assignment

Note nindent value - 6

spec:
  selector:
    matchLabels:
    {{ toYaml $deployment.selectorLabels | nindent 6 }}

4 Blank Spaces from Left + 2 TAB Spaces (standard K8s object hierarchy)

Few More Examples

Note nindent value = 8

  template:
    metadata:
      labels:
      {{ toYaml $deployment.selectorLabels | nindent 8 }}

Note nindent value = 4

metadata:
  name: {{ $deployment.name }}
  namespace: {{ $deployment.namespace }}
  labels:
  {{ toYaml $deployment.labels | nindent 4 }}

Lookup
- Format = lookup (apiVersion, kind, namespace, name)
- apiVersion and kind are mandatory parameters
- namespace parameter empty implies all k8s namespaces
- name parameter empty implies all k8s resources of the specified kind

Examples

Deployment

{{ $deployment := .Values.deployment }}
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ $deployment.name }}
  namespace: {{ $deployment.namespace }}
  labels:
  {{ toYaml $deployment.labels | nindent 4 }}
spec:
  selector:
    matchLabels:
    {{ toYaml $deployment.selectorLabels | nindent 6 }}
  replicas: {{ $deployment.replicas }}
  strategy:
    type: {{ $deployment.strategyType }}
    rollingUpdate:
      maxSurge: {{ $deployment.maxSurge }}
      maxUnavailable: {{ $deployment.maxUnavailable }}
  template:
    metadata:
      labels:
      {{ toYaml $deployment.selectorLabels | nindent 8 }}
    spec:
      nodeSelector:
      {{ toYaml $deployment.nodeSelector | nindent 8 }}
      {{ if $deployment.imagePullSecrets }}
      {{- range $secret := $deployment.imagePullSecrets }}
      imagePullSecrets:
      - name: {{ $secret.name }}
      {{- end}}
      {{ end }}
      containers:
      {{- range $container := $deployment.containers }}
      - name: {{ $container.name }}
        image: {{ $container.image }}
        imagePullPolicy: {{ $container.imagePullPolicy }}
        resources:
          requests:
            memory: {{ $container.memoryRequest }}
            cpu: {{ $container.cpuRequest }}
          limits:
            memory: {{ $container.memoryLimit }}
            cpu: {{ $container.cpuLimit }}
        {{ if and $container.readinessPort $container.readinessPath}}
        readinessProbe:
          httpGet:
            port: {{ $container.readinessPort }}
            path: {{ $container.readinessPath }}
        {{ end }}
        {{ if and $container.livenessPort $container.livenessPath }}
        livenessProbe:
          httpGet:
            port: {{ $container.livenessPort }}
            path: {{ $container.livenessPath }}
        {{ end }}
        env:
        {{- range $env := $container.env }}
        - name: {{ $env.name }}
          valueFrom:
            secretKeyRef:
              key: {{ $env.valueKey }}
              name: {{ $env.valueSecret }}
        {{- end }}
        ports:
        {{- range $containerPort := $container.containerPorts }}
        - containerPort: {{ $containerPort }}
        {{- end }}
      {{- end }}

Service

{{ $service := .Values.service }}
apiVersion: v1
kind: Service
metadata:
  name: {{ $service.name }}
  namespace: {{ $service.namespace }}
spec:
  selector:
  {{ toYaml $service.selector | nindent 4}}
  ports:
  {{ range $port := $service.ports }}
  - protocol: {{ $port.protocol }}
    port: {{ $port.port }}
    targetPort: {{ $port.targetPort }}
  {{ end }}
  type: ClusterIP

RBAC

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: {{ .Values.developer.roleName }}
  namespace: {{ .Values.developer.roleNamespace }}
rules:
{{- range $rule := .Values.developer.rules}}
- apiGroups: {{ $rule.apiGroups }}
  resources: {{ $rule.resources }}
  verbs: {{ $rule.verbs }}
{{- end }}

---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: {{ .Values.developer.bindingName }}
  namespace: {{ .Values.developer.bindingNamespace }}
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: {{ .Values.developer.roleName }}
subjects:
{{- range $subject := .Values.developer.subjects}}
- apiGroup: rbac.authorization.k8s.io
  name: {{  $subject.name }}
  kind: {{  $subject.kind }}
{{- end }}

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: {{ .Values.manager.roleName }}
  namespace: {{ .Values.manager.roleNamespace }}
rules:
{{- range $rule := .Values.developer.rules}}
- apiGroups: {{ $rule.apiGroups }}
  resources: {{ $rule.resources }}
  verbs: {{ $rule.verbs }}
{{- end }}

---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: {{ .Values.manager.bindingName }}
  namespace: {{ .Values.manager.bindingNamespace }}
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: {{ .Values.manager.roleName }}
subjects:
{{- range $subject := .Values.manager.subjects}}
- apiGroup: rbac.authorization.k8s.io
  name: {{ $subject.name }}
  kind: {{ $subject.kind }}
{{- end }}

# Check for existence of the ClusterRoleBinding resource with the name - aks-workshop-cluster-admin-bindings in all k8s namespaces
{{if not (lookup "rbac.authorization.k8s.io/v1" "ClusterRoleBinding" "" "aks-workshop-cluster-admin-bindings") }}
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: {{ .Values.clusteradmin.name }}
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: {{ .Values.clusteradmin.roleName }}
subjects:
- apiGroup: rbac.authorization.k8s.io
  name: {{ (index .Values.clusteradmin.subjects 0).name}}
  kind: {{ (index .Values.clusteradmin.subjects 0).kind}}
{{ end }}

Ingress

{{ $ingress := .Values.ingress }}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: {{ $ingress.name }}    
  namespace: {{ $ingress.namespace }}  
  annotations:
    kubernetes.io/ingress.class: {{ $ingress.annotations.ingressClass }}
    {{ if $ingress.annotations.rewriteTarget }}
    nginx.ingress.kubernetes.io/rewrite-target: {{ $ingress.annotations.rewriteTarget }}
    {{ end }}  
    {{ if $ingress.annotations.enableCors }}
    nginx.ingress.kubernetes.io/enable-cors: {{ $ingress.annotations.enableCors | quote }}
    {{ end }}  
    {{ if $ingress.annotations.proxyBodySize }}
    nginx.ingress.kubernetes.io/proxy-body-size: {{ $ingress.annotations.proxyBodySize }}
    {{ end }}
    {{ if $ingress.annotations.backendProtocol }}
    nginx.ingress.kubernetes.io/backend-protocol: {{ $ingress.annotations.backendProtocol }}
    {{ end }}
    {{ if $ingress.annotations.sslpassThrough }}
    nginx.ingress.kubernetes.io/ssl-passthrough: {{ $ingress.annotations.sslpassThrough | quote }}
    {{ end }}    
spec:
  rules:
  {{- range $host := $ingress.hosts }}
  - host: {{ $host.name}}
    http:
      paths:
      {{- range $path := $host.paths }}
      - path: {{ $path.path }}
        pathType: {{ $path.pathType }}
        backend:
          service:
            name: {{ $path.service }}
            port:
              number: {{ $path.port }}
      {{- end }}
  {{- end }}
  {{ if $ingress.tls }}
  tls:
  {{- range $tls := $ingress.tls }}
  - hosts:
    {{- range $tlsHost := $tls.hosts }}
    - {{ $tlsHost | quote }}
    {{- end }}
    secretName: {{ $tls.secretName }}
  {{- end }}
  {{ end }}

Values for the Chart

Examples

Deployment

deployment:
  name: ratingsapi-deploy
  namespace: aks-workshop-dev
  labels:
    app: ratingsapi-deploy
  selectorLabels:
    app: ratingsapi-pod    
  replicas: 2
  strategyType: RollingUpdate
  maxSurge: 1
  maxUnavailable: 1
  nodeSelector:
    agentpool: aksapipool
  containers:
  - name: ratingsapi-app
    image: <acrName>.azurecr.io/ratings-api:v1.0.0
    imagePullPolicy: IfNotPresent
    readinessPort: 3000
    readinessPath: /healthz
    livenessPort: 3000
    livenessPath: /healthz
    memoryRequest: "64Mi"
    cpuRequest: "100m"
    memoryLimit: "256Mi"
    cpuLimit: "200m"
    containerPorts: [3000]    
    env:          
    - name: MONGODB_URI
      valueKey: MONGOCONNECTION
      valueSecret: aks-workshop-mongo-secret

Service

service:
  name: ratingsapi-service
  namespace: aks-workshop-dev
  selector:
    app: ratingsapi-pod
  type: ClusterIP
  ports:
  - protocol: TCP
    port: 80
    targetPort: 3000

RBAC

clusteradmin:
  name: aks-workshop-cluster-admin-bindings
  roleName: cluster-admin
  subjects:
  - name: <>
    kind: User

developer:
  roleName: aks-workshop-developer-roles
  roleNamespace: aks-workshop-dev
  rules:
  - apiGroups: ["", "apps", "networking.k8s.io"]
    resources: ["configmaps", "pods", "pods/exec", "pods/log", "deployments", "services", "events", "ingresses"]
    verbs: ["create", "delete", "deletecollection", "get", "list", "patch", "update", "watch"]
  bindingName: aks-workshop-developer-rb
  bindingNamespace: aks-workshop-dev
  subjects:
  - name: <AzureAD_Group_Name>
    kind: Group

manager:
  roleName: aks-workshop-manager-roles
  roleNamespace: aks-workshop-dev
  rules:
  - apiGroups: ["", "apiextensions.k8s.io", "apps", "autoscaling", "batch", "events.k8s.io", "networking.k8s.io", "policy", "rbac.authorization.k8s.io", "scheduling.k8s.io"]
    resources: ["configmaps", "endpoints", "events", "limitranges", "persistentvolumeclaims", "pods", "resourcequotas", "serviceaccounts", "namespaces", "services", "customresourcedefinitions", "daemonsets", "deployments", "replicasets", "statefulsets", "horizontalpodautoscalers", "cronjobs", "jobs", "events", "ingresses", "networkpolicies", "poddisruptionbudgets", "rolebindings", "roles", "priorityclasses"]
    verbs: ["create", "delete", "deletecollection", "get", "list", "patch", "update", "watch"]
  - apiGroups: ["metrics.k8s.io"]
    resources: ["nodes", "pods"]
    verbs: ["get", "list"]
  bindingName: aks-workshop-manager-rb
  bindingNamespace: aks-workshop-dev
  subjects:
  - name: <AzureAD_Group_Name>
    kind: Group

Ingress

ingress:
  name: aks-workshop-ingress
  namespace: aks-workshop-dev
  annotations:
    ingressClass: nginx
    proxyBodySize: "10m"
    enableCors: "true"
    rewriteTarget: /$1    
  hosts:
  - name: <dns-server>
    paths:    
    - path: /?(.*)
      pathType: Prefix
      service: ratingsweb-service
      port: 80

Install/Upgrade the Chart

helm install <chart-name> -n aks-workshop-dev ./<chart-name>/ -f ./<chart-name>/values-dev.yaml

helm upgrade <chart-name> -n aks-workshop-dev ./<chart-name>/ -f ./<chart-name>/values-dev.yaml

UnInstall the Chart

helm uninstall <chart-name>

Integration with Azure DevOps

Helm deployment Task in Azure DevOps

https://docs.microsoft.com/en-us/azure/devops/pipelines/tasks/deploy/helm-deploy?view=azure-devops

Deploy Cloud Native Apps on AKS – Happy Helming

Introduction

What this article covers

Components

Chart.yaml

values.yaml

Chart Templates

Let us Get into some Action

Create Helm Chart

Folder Structure

Configure Chart Release

Define a Chart Template

Conditions

Loops

Assign Single Key/Value pair

Assign Multiple Key/Value pairs

Lookup

Examples

Deployment

Service

RBAC

Ingress

Values for the Chart

Examples

Deployment

Service

RBAC

Ingress

Install/Upgrade the Chart

UnInstall the Chart

Integration with Azure DevOps

References

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