將 ConfigMap 做為 Helm volume mount 的來源

有用過 container 的朋友相信對於 volume mount 有一定的了解，如果有用過 db 類型的 container (mysql、mongodb…) 對於透過 docker-entrypoint-initdb.d 來建立初始資料應該也不陌生，但相同機制在 Helm 中該如何實現呢？！

因為 Helm 只是用來管理 Kubernetes service 的工具，我才疏學淺不知道該如何正確將初始資料用的檔案隨著 Helm 部署，後來查到可以將設定內容存至 ConfigMap 中，再 mount 至 container 中，趁著印憶猶新趕緊紀錄一下，不然本來就沒有很了解前因後果，一定很快就忘了

基本環境說明

macOS Mojave 10.15.2
docker desktop community 2.2.0.0(42247)
Docker Engine 19.03.5
Kubernetes v1.15.5
Helm v2.16.1

原始 helm (以 mysql 為例)

templates/deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "yowkochart.fullname" . }}
  labels:
{{ include "yowkochart.labels" . | indent 4 }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app.kubernetes.io/name: {{ include "yowkochart.name" . }}
      app.kubernetes.io/instance: {{ .Release.Name }}
  template:
    metadata:
      labels:
        app.kubernetes.io/name: {{ include "yowkochart.name" . }}
        app.kubernetes.io/instance: {{ .Release.Name }}
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - name: http
              containerPort: 3306
              protocol: TCP
            env:
            - name: MYSQL_ROOT_PASSWORD
              value: {{.Values.mysql.password}}

templates/service.yaml

apiVersion: v1
kind: Service
metadata:
  name: {{ include "yowkochart.fullname" . }}
  labels:
{{ include "yowkochart.labels" . | indent 4 }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: http
      protocol: TCP
      name: mysql
  selector:
    app.kubernetes.io/name: {{ include "yowkochart.name" . }}
    app.kubernetes.io/instance: {{ .Release.Name }}

values.yaml

replicaCount: 1

image:
  repository: mysql
  tag: 5.7.28
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 3306

mysql:
  password: pass.123

Chart.yaml

apiVersion: v1
appVersion: "1.0"
description: A Helm chart for Kubernetes
name: yowkochart
version: 0.1.0

僅有預設資料庫

1default

設定方式

建立 ConfigMap - templates/initial-configmap.yaml

sql script 內容請依實際需求自行調整

apiVersion: v1
kind: ConfigMap
metadata:
  name: "mysql-init-configmap"
data:
  init.sql: |-
    create database if not exists yowkodb;

    USE yowkodb;

    CREATE TABLE IF NOT EXISTS Users
    (
        Id int auto_increment
            primary key,
        Name varchar(20) not null default '',
        Gender bool default 1 not null,
        DateUpdated datetime default current_timestamp() not null,
        DateCreated datetime default current_timestamp() not null
    );

    ALTER TABLE Users AUTO_INCREMENT = 1001;

    INSERT INTO yowkodb.Users (Name, Gender) VALUES ('yowko', 1);
    INSERT INTO yowkodb.Users (Name, Gender) VALUES ('ann', 0);

修改 Deployment - templates/deployment.yaml

以下是我多方嘗試得到的結果，如果有錯敬請指教

containers.volumeMounts.name 需要與 volume.name 相同
containers.volumeMounts.mountPath 需要指定到 file name
containers.volumeMounts.subPath 與 containers.volumeMounts.mountPath 的 file name 相同

volumes.configMap.name 與 templates/initial-configmap.yaml 的 metadata.name 相同

apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ include "yowkochart.fullname" . }}
labels:
{{ include "yowkochart.labels" . | indent 4 }}
spec:
replicas: {{ .Values.replicaCount }}
selector:
matchLabels:
  app.kubernetes.io/name: {{ include "yowkochart.name" . }}
  app.kubernetes.io/instance: {{ .Release.Name }}
template:
metadata:
  labels:
    app.kubernetes.io/name: {{ include "yowkochart.name" . }}
    app.kubernetes.io/instance: {{ .Release.Name }}
spec:
  containers:
    - name: {{ .Chart.Name }}
      image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
      imagePullPolicy: {{ .Values.image.pullPolicy }}
      ports:
        - name: http
          containerPort: 3306
          protocol: TCP
      env:
      - name: MYSQL_ROOT_PASSWORD
        value: {{.Values.mysql.password}}
      volumeMounts:
      - name: init-scripts
        mountPath: /docker-entrypoint-initdb.d/init.sql
        subPath: init.sql
  volumes:
  - name: init-scripts
    configMap:
      name: mysql-init-configmap

安裝測試

kubectl 指令中的 pod name 請依實際狀況調整

databases

語法

kubectl exec -it {pod name} -- mysql -h {mysql ip} -P {mysql port} -u root -p{密碼} -e "show databases"

範例

kubectl exec -it pod/mysql-yowkochart-5474d9dd57-hg2qg -- mysql -h 127.0.0.1 -P 3306 -u root -ppass.123 -e "show databases"

2databases

data

語法

kubectl exec -it {pod name} -- mysql -h {mysql ip} -P {mysql port} -u root -p{密碼} -e "select * from {db name}.{table name}"

範例

kubectl exec -it pod/mysql-yowkochart-5474d9dd57-hg2qg -- mysql -h 127.0.0.1 -P 3306 -u root -ppass.123 -e "select * from yowkodb.Users"

3data

心得

雖然東拼西湊有達成想要的目標，但還是有些做法搞不清來龍去脈：

為什麼 mountPath 要加上 filename
為什麼需要 subPath

另外我也不確定這是不是個好的方式，畢竟需要調整 initial script 的內容就變成要改 Helm Chart，我個人覺得 Helm Chart 只是簡化管理的工具，不適合把頻繁異動的內容往裡頭塞，如果後續異動頻率較高可能就得考慮其他做法了

文章目錄