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

  1. macOS Mojave 10.15.2
  2. docker desktop community 2.2.0.0(42247)
  3. Docker Engine 19.03.5
  4. Kubernetes v1.15.5
  5. Helm v2.16.1
  6. 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

  1. 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);
    
  2. 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.subPathcontainers.volumeMounts.mountPath 的 file name 相同
    • volumes.configMap.nametemplates/initial-configmap.yamlmetadata.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
    
  3. 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:

  1. 為什麼 mountPath 要加上 filename
  2. 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

參考資源

  1. Volumes
  2. configmap file mount path results in command not found error