本文
上篇文章中我們介紹了 Helm 的概念，包含了 Helm Chart, Config 以及 Released，而要瞭解這些概念最好的方式就是直接參考一個實際的範例，
首先根據官方教學，安裝 Helm 指令到系統中, 多種安裝方法，擇一即可
curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bash
因此我們會使用 Helm create 指令創建一個基本的 Helm Chart，並從中瞭解其架構
$ helm create ithome
$ tree ithome
ithome
├── Chart.yaml
├── charts
├── templates
│ ├── NOTES.txt
│ ├── _helpers.tpl
│ ├── deployment.yaml
│ ├── hpa.yaml
│ ├── ingress.yaml
│ ├── service.yaml
│ ├── serviceaccount.yaml
│ └── tests
│ └── test-connection.yaml
└── values.yaml
3 directories, 10 files
一個全新產生的 Helm Chart 內總共有 10 個檔案， 3個資料夾
裡面跟 Kubernetes 有關的物件資源有五個，包含 deployment.yaml, hpa.yaml, ingress.yaml, service.yaml, serviceaccount.yaml, 這些 Yaml 內容都含有 Go Template 的內容
$ cat ithome/templates/hpa.yaml
{{- if .Values.autoscaling.enabled }}
apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
name: {{ include "ithome.fullname" . }}
labels:
{{- include "ithome.labels" . | nindent 4 }}
spec:
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment
name: {{ include "ithome.fullname" . }}
minReplicas: {{ .Values.autoscaling.minReplicas }}
maxReplicas: {{ .Values.autoscaling.maxReplicas }}
metrics:
{{- if .Values.autoscaling.targetCPUUtilizationPercentage }}
- type: Resource
resource:
name: cpu
targetAverageUtilization: {{ .Values.autoscaling.targetCPUUtilizationPercentage }}
{{- end }}
{{- if .Values.autoscaling.targetMemoryUtilizationPercentage }}
- type: Resource
resource:
name: memory
targetAverageUtilization: {{ .Values.autoscaling.targetMemoryUtilizationPercentage }}
{{- end }}
{{- end }}
此外還可以看到最外面有一個 Values.yaml，裡面就包含各式各樣的變數以及預設值，
╰─$ cat values.yaml
# Default values for ithome.
# 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: ""
podAnnotations: {}
podSecurityContext: {}
# fsGroup: 2000
securityContext: {}
# capabilities:
# drop:
# - ALL
# readOnlyRootFilesystem: true
# runAsNonRoot: true
# runAsUser: 1000
service:
type: ClusterIP
port: 80
ingress:
enabled: false
annotations: {}
# kubernetes.io/ingress.class: nginx
# kubernetes.io/tls-acme: "true"
hosts:
- host: chart-example.local
paths: []
tls: []
# - secretName: chart-example-tls
# hosts:
# - chart-example.local
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: false
minReplicas: 1
maxReplicas: 100
targetCPUUtilizationPercentage: 80
# targetMemoryUtilizationPercentage: 80
nodeSelector: {}
tolerations: []
affinity: {}
如果想要安裝這個 Helm Chart 到系統內，依序執行下列指令
- 創建測試用 namespace
- 將該 Helm Chart 安裝到系統中的 ithome namespace 並且將該 released 命名為 ithome. 來源 Helm Charts 是當前資料夾
.
$ kubectl create ns ithome namespace/ithome created
$ helm install --namespace ithome ithome .
NAME: ithome
LAST DEPLOYED: Tue Sep 8 21:54:12 2020
NAMESPACE: ithome
STATUS: deployed
REVISION: 1
NOTES:
1. Get the application URL by running these commands:
export POD_NAME=$(kubectl get pods --namespace ithome -l "app.kubernetes.io/name=ithome,app.kubernetes.io/instance=ithome" -o jsonpath="{.items[0].metadata.name}")
echo "Visit http://127.0.0.1:8080 to use your application"
kubectl --namespace ithome port-forward $POD_NAME 8080:80
$ kubectl -n ithome get all 1 ↵
NAME READY STATUS RESTARTS AGE
pod/ithome-5cc87ff5f4-xnpvh 1/1 Running 0 36s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/ithome ClusterIP 10.43.95.165 <none> 80/TCP 36s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/ithome 1/1 1 1 36s
NAME DESIRED CURRENT READY AGE
replicaset.apps/ithome-5cc87ff5f4 1 1 1 36s
再來則是觀看系統上安裝的哪些的 Helm Chart，可以透過 helm ls 的方式來觀看，如果有不同的 namespace 都要透過 -n 來指定
$ helm -n ithome ls
NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION
ithome ithome 1 2020-09-08 21:54:12.803147 -0700 PDT deployed ithome-0.1.0 1.16.0
最後是一系列好用的指令，helm get 可以取得該 Released 上的各種資料
$ helm get --help
Usage:
helm get [command]
Available Commands:
all download all information for a named release
hooks download all hooks for a named release
manifest download the manifest for a named release
notes download the notes for a named release
values download the values file for a named release
最簡單的兩個範例就是 manifest 以及 values, 透過 manifest 我們可以直接觀察到最後安裝到系統內的 YAML 檔案長什麼樣子
譬如
$ helm -n ithome get manifest ithome
---
# Source: ithome/templates/serviceaccount.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: ithome
labels:
helm.sh/chart: ithome-0.1.0
app.kubernetes.io/name: ithome
app.kubernetes.io/instance: ithome
app.kubernetes.io/version: "1.16.0"
app.kubernetes.io/managed-by: Helm
---
# Source: ithome/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
name: ithome
labels:
helm.sh/chart: ithome-0.1.0
app.kubernetes.io/name: ithome
app.kubernetes.io/instance: ithome
app.kubernetes.io/version: "1.16.0"
app.kubernetes.io/managed-by: Helm
spec:
type: ClusterIP
ports:
- port: 80
targetPort: http
protocol: TCP
name: http
selector:
app.kubernetes.io/name: ithome
app.kubernetes.io/instance: ithome
---
# Source: ithome/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: ithome
labels:
helm.sh/chart: ithome-0.1.0
app.kubernetes.io/name: ithome
app.kubernetes.io/instance: ithome
app.kubernetes.io/version: "1.16.0"
app.kubernetes.io/managed-by: Helm
spec:
replicas: 1
selector:
matchLabels:
app.kubernetes.io/name: ithome
app.kubernetes.io/instance: ithome
template:
metadata:
labels:
app.kubernetes.io/name: ithome
app.kubernetes.io/instance: ithome
spec:
serviceAccountName: ithome
securityContext:
{}
containers:
- name: ithome
securityContext:
{}
image: "nginx:1.16.0"
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 80
protocol: TCP
livenessProbe:
httpGet:
path: /
port: http
readinessProbe:
httpGet:
path: /
port: http
resources:
{}
可以看到這邊就是上述那些充滿 Go Template 格式Yaml渲染後的結果，我們也可以使用 helm get values 來看一次目前是否有任何客製化的設定
helm -n ithome get values ithome
USER-SUPPLIED VALUES:
null
根據這個指令我們可以觀察到本次安裝沒有任何客製化的變動，採用的是最原生的 Values.yaml.
因此接下來我們嘗試升級該 Release，並且修改裡面的設定值
$ helm -n ithome upgrade ithome --set service.type=NodePort .
Release "ithome" has been upgraded. Happy Helming!
NAME: ithome
LAST DEPLOYED: Tue Sep 8 22:02:49 2020
NAMESPACE: ithome
STATUS: deployed
REVISION: 2
NOTES:
1. Get the application URL by running these commands:
export NODE_PORT=$(kubectl get --namespace ithome -o jsonpath="{.spec.ports[0].nodePort}" services ithome)
export NODE_IP=$(kubectl get nodes --namespace ithome -o jsonpath="{.items[0].status.addresses[0].address}")
echo http://$NODE_IP:$NODE_PORT
指令中我們透過 helm upgrade 的方式來升級已經存在的 Released ithome, 我們透過 --set service.type=NodePort 的方式去覆蓋掉 values.yaml 裡面的預設數值(這邊也可以直接修改 values.yaml, 或是產生一個全新的 Yaml 然後送給 Helm 指令)。最後我們指令來源 Helm Chart 的位置 . (當前目錄)。
可以看到上述指令後來輸出一些部署的資訊，包含該 Relased 是第二個版本，部署的時間，當前狀態，什麼 namespace.
一切完畢之後，我們再度使用 helm get values 的指令來看看是否有什麼變化
$ helm -n ithome get values ithome
USER-SUPPLIED VALUES:
service:
type: NodePort
$ kubectl -n ithome get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ithome NodePort 10.43.95.165 <none> 80:30232/TCP 9m20s
這時候可以很明確地看到，當前運行的 ithome released 有一個客製化的選項，就是我們前述所輸入的 service.type ，同時觀察 kuberctl -n ithome get svc 也真的看到 service 的內容變成 NodePort.
Helm 可以操作與設定的東西非常多，這邊的設定只是一個非常簡單的範例，實務上有非常多的事情要處理，也有非常多的小麻煩，譬如當你的客製化資訊本身有雙引號或是個 JSON 字串，你的腳本該怎麼處理。 Helm 要如何跟應用程式整理，開發人員跟維護人員誰要負責設計與維護應用程式的 Helm Chart, 基本上都沒有一個完整答案，只要能夠讓你輕鬆上班，簡單部署，達到薪水小偷的境界就是一個好的解決方案。