# Helm Deploy to K8s

## Pre Requirements
1. Manual create Namespace
2. Manual create TLS Secrets (for ingress https)

## Step
### 1. Create Helm Template
建立 helm 的設定檔

helm create {template name}

ex.
helm create customer

**Template Name:** 會影響 Charts.yaml 裡面的名稱，從 Charts 出發的名稱都會被這個影響到

[目錄結構](https://helm.sh/zh/docs/helm/helm_create/)

### 2. Update Values.yaml
基本上就是把之後需要被取代掉或可重複使用的值在這邊定義，後續 helm 會自動把值填入到 templates 資料夾裡面的各個 yaml

# Default values for schedulev2.
# This is a YAML-formatted file.
# Declare variables to be passed into your templates.

replicaCount: 1

environment: ""

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

labels: 
  role: ""
  app: "customer"

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

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: ""

podAnnotations: {}

podSecurityContext: {}
  # fsGroup: 2000

securityContext: {}
  # capabilities:
  #   drop:
  #   - ALL
  # readOnlyRootFilesystem: true
  # runAsNonRoot: true
  # runAsUser: 1000

service:
  type: ClusterIP
  port: 80

ingress:
  enabled: true
  className: ""
  annotations: 
    kubernetes.io/ingress.class: addon-http-application-routing
    # kubernetes.io/ingress.class: nginx
    # kubernetes.io/tls-acme: "true"
  hosts:
    - host: test.domain.com
      paths:
        - path: /
          pathType: ImplementationSpecific
  tls: 
   - secretName: tls-secrets # 需預先建立在 k8s，且 name 需跟這裡一樣
     hosts:
       - test.domain.com

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: 200m
    memory: 128Mi
  requests:
    cpu: 100m
    memory: 64Mi

livenessProbe:
  enabled: false
  setting:
    httpGet: 
      path: /
      port: 80
    initialDelaySeconds: 15 
    timeoutSeconds: 2 
readinessProbe:
  enabled: false
  setting:
    httpGet: 
      path: /
      port: 80
    initialDelaySeconds: 15 
    timeoutSeconds: 2 

# if not set auto scaling, pod will use "replicaCount" set at deployment
autoscaling:
  enabled: false
  minReplicas: 1
  maxReplicas: 100
  targetCPUUtilizationPercentage: 80
  # targetMemoryUtilizationPercentage: 80

nodeSelector: {}

tolerations: []

affinity: {}

### 3. Update _helpers.tpl
_helpers.tpl 是一個客製 template 的檔案，可以把一些常用的參數放在這裡，就不用每個檔案都重寫一份，而且也可以寫一些條件式之類的

{{/*
Create the name of the service to use
Example: {environment}-{fullName} => dev-customer
如果要使用的話，可以在別的檔案內寫成這樣: {{ include "customer.namespace" . }}
*/}}
{{- define "customer.namespace" -}}
{{- default "" (printf "%s-%s" .Values.environment (include "customer.fullname" .)) | lower }}
{{- end }}

### 4. Create Deployment.yaml
基本上就是把現有的 deployment.yaml 複製過來，然後把參數用 values.yaml 的值替換掉

apiVersion: "apps/v1"
kind: "Deployment"
metadata:
  # 把 template 裡面定義的 customer.appFullName 注入到這裡，後面也可以用參數接起來再利用
  name: {{ include "customer.appFullName" . }} 
  namespace: {{ include "customer.namespace" . }}
  labels:
    # 把 template 裡面定義的 customer.labels 注入到這裡，並且會從第一個字開始空4格
    {{- include "customer.labels" . | nindent 4 }} 
    # 把 values.yaml 裡面定義的 labels.role 注入到這邊
    role: {{ .Values.labels.role }} 
    app: {{ .Values.labels.app }} 
    env: {{ .Values.environment }} 
spec:
  # 如果 values.yaml 裡面的 autoscaling.enabled 是 false 則會 render 出 if-end 中間的區塊
  {{- if not .Values.autoscaling.enabled }} #
  replicas: {{ .Values.replicaCount }}
  {{- end }}
  progressDeadlineSeconds: 300
  minReadySeconds: 5
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  revisionHistoryLimit: 20      
  selector:
    matchLabels:
      role: {{ .Values.labels.role }}
      app: {{ .Values.labels.app }} 
      env: {{ .Values.environment }} 
  template:
    metadata:
      labels:
        role: {{ .Values.labels.role }}
        app: {{ .Values.labels.app }} 
        env: {{ .Values.environment }} 
    spec:
      restartPolicy: "Always"
      containers:
        - name: "app"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          # 組合字串並加上額外文字
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          env:
            - name: ASPNETCORE_ENVIRONMENT
              # 將 | 前面的文字轉換為小寫
              value: {{ .Values.environment | lower }}
          ports:
            - name: http
              protocol: TCP
              containerPort:  {{ .Values.service.port }}
          resources:
            # 把 values.yaml 裡面定義的 resources 注入到這邊，並且轉換成 yaml 格式，且每行都會空12格
            {{- toYaml .Values.resources | nindent 12 }}
          {{- if .Values.livenessProbe.enabled }}
          livenessProbe:
            {{- toYaml .Values.livenessProbe.setting | nindent 12 }}
          {{- end}}
          {{- if .Values.readinessProbe.enabled }}
          readinessProbe:
            {{- toYaml .Values.readinessProbe.setting | nindent 12 }}
          {{- end}}

### 5. Create Service.yaml
基本上就是把現有的 Service.yaml 複製過來，然後把參數用 values.yaml 的值替換掉

apiVersion: v1
kind: Service
metadata:
  name: {{ include "customer.appFullName" . }}
  namespace: {{ include "customer.namespace" . }}
  labels:
    {{- include "customer.labels" . | nindent 4 }}
    role: {{ .Values.labels.role }}
    app: {{ .Values.labels.app }} 
    env: {{ .Values.environment }} 
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: http
      protocol: TCP
      name: http
  selector:
    role: {{ .Values.labels.role }}
    app: {{ .Values.labels.app }} 
    env: {{ .Values.environment }} 

### 6. Create Ingress.yaml
直接用檔案預設產生的來改比較快，因為 Ingress 比較容易踩到 SemVer 版本的問題

### 7. Deploy to K8s

先透過 command 建立好不會透過 CICD 每次都異動的資源

# Create namespace in K8s
# Create tls secrets in k8s

透過 helm 佈署到 k8s 上

helm upgrade --install --namespace {Helm Namespace} {Release Name} {Chart File Path}

[Helm Upgrade](https://helm.sh/docs/helm/helm_upgrade/)

###### tags: `Helm`