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Example: Deploying WordPress and MySQL with Persistent Volumes

This tutorial shows you how to deploy a WordPress site and a MySQL database using Minikube. Both applications use PersistentVolumes and PersistentVolumeClaims to store data.

A PersistentVolume (PV) is a piece of storage in the cluster that has been manually provisioned by an administrator, or dynamically provisioned by Kubernetes using a StorageClass. A PersistentVolumeClaim (PVC) is a request for storage by a user that can be fulfilled by a PV. PersistentVolumes and PersistentVolumeClaims are independent from Pod lifecycles and preserve data through restarting, rescheduling, and even deleting Pods.

警告: This deployment is not suitable for production use cases, as it uses single instance WordPress and MySQL Pods. Consider using WordPress Helm Chart to deploy WordPress in production.
注意: The files provided in this tutorial are using GA Deployment APIs and are specific to kubernetes version 1.9 and later. If you wish to use this tutorial with an earlier version of Kubernetes, please update the API version appropriately, or reference earlier versions of this tutorial.

教程目标

  • Create PersistentVolumeClaims and PersistentVolumes
  • Create a kustomization.yaml with
    • a Secret generator
    • MySQL resource configs
    • WordPress resource configs
  • Apply the kustomization directory by kubectl apply -k ./
  • Clean up

准备开始

你必须拥有一个 Kubernetes 的集群,同时你的 Kubernetes 集群必须带有 kubectl 命令行工具。 如果你还没有集群,你可以通过 Minikube 构建一 个你自己的集群,或者你可以使用下面任意一个 Kubernetes 工具构建:

要获知版本信息,请输入 kubectl version.

The example shown on this page works with kubectl 1.14 and above.

Download the following configuration files:

  1. mysql-deployment.yaml

  2. wordpress-deployment.yaml

Create PersistentVolumeClaims and PersistentVolumes

MySQL and Wordpress each require a PersistentVolume to store data. Their PersistentVolumeClaims will be created at the deployment step.

Many cluster environments have a default StorageClass installed. When a StorageClass is not specified in the PersistentVolumeClaim, the cluster’s default StorageClass is used instead.

When a PersistentVolumeClaim is created, a PersistentVolume is dynamically provisioned based on the StorageClass configuration.

警告: In local clusters, the default StorageClass uses the hostPath provisioner. hostPath volumes are only suitable for development and testing. With hostPath volumes, your data lives in /tmp on the node the Pod is scheduled onto and does not move between nodes. If a Pod dies and gets scheduled to another node in the cluster, or the node is rebooted, the data is lost.
注意: If you are bringing up a cluster that needs to use the hostPath provisioner, the --enable-hostpath-provisioner flag must be set in the controller-manager component.
注意: If you have a Kubernetes cluster running on Google Kubernetes Engine, please follow this guide.

Create a kustomization.yaml

Add a Secret generator

A Secret is an object that stores a piece of sensitive data like a password or key. Since 1.14, kubectl supports the management of Kubernetes objects using a kustomization file. You can create a Secret by generators in kustomization.yaml.

Add a Secret generator in kustomization.yaml from the following command. You will need to replace YOUR_PASSWORD with the password you want to use.

cat <<EOF >./kustomization.yaml
secretGenerator:
- name: mysql-pass
  literals:
  - password=YOUR_PASSWORD
EOF

Add resource configs for MySQL and WordPress

The following manifest describes a single-instance MySQL Deployment. The MySQL container mounts the PersistentVolume at /var/lib/mysql. The MYSQL_ROOT_PASSWORD environment variable sets the database password from the Secret.

application/wordpress/mysql-deployment.yaml
apiVersion: v1
kind: Service
metadata:
  name: wordpress-mysql
  labels:
    app: wordpress
spec:
  ports:
    - port: 3306
  selector:
    app: wordpress
    tier: mysql
  clusterIP: None
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
  labels:
    app: wordpress
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: wordpress-mysql
  labels:
    app: wordpress
spec:
  selector:
    matchLabels:
      app: wordpress
      tier: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: wordpress
        tier: mysql
    spec:
      containers:
      - image: mysql:5.6
        name: mysql
        env:
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-pass
              key: password
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim

The following manifest describes a single-instance WordPress Deployment. The WordPress container mounts the PersistentVolume at /var/www/html for website data files. The WORDPRESS_DB_HOST environment variable sets the name of the MySQL Service defined above, and WordPress will access the database by Service. The WORDPRESS_DB_PASSWORD environment variable sets the database password from the Secret kustomize generated.

application/wordpress/wordpress-deployment.yaml
apiVersion: v1
kind: Service
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  ports:
    - port: 80
  selector:
    app: wordpress
    tier: frontend
  type: LoadBalancer
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: wp-pv-claim
  labels:
    app: wordpress
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  selector:
    matchLabels:
      app: wordpress
      tier: frontend
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: wordpress
        tier: frontend
    spec:
      containers:
      - image: wordpress:4.8-apache
        name: wordpress
        env:
        - name: WORDPRESS_DB_HOST
          value: wordpress-mysql
        - name: WORDPRESS_DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-pass
              key: password
        ports:
        - containerPort: 80
          name: wordpress
        volumeMounts:
        - name: wordpress-persistent-storage
          mountPath: /var/www/html
      volumes:
      - name: wordpress-persistent-storage
        persistentVolumeClaim:
          claimName: wp-pv-claim
  1. Download the MySQL deployment configuration file.

      curl -LO https://k8s.io/examples/application/wordpress/mysql-deployment.yaml
  2. Download the WordPress configuration file.

      curl -LO https://k8s.io/examples/application/wordpress/wordpress-deployment.yaml
  3. Add them to kustomization.yaml file.

      cat <<EOF >>./kustomization.yaml
      resources:
        - mysql-deployment.yaml
        - wordpress-deployment.yaml
      EOF

Apply and Verify

The kustomization.yaml contains all the resources for deploying a WordPress site and a MySQL database. You can apply the directory by

kubectl apply -k ./

Now you can verify that all objects exist.

  1. Verify that the Secret exists by running the following command:

      kubectl get secrets

    The response should be like this:

      NAME                    TYPE                                  DATA   AGE
      mysql-pass-c57bb4t7mf   Opaque                                1      9s
  2. Verify that a PersistentVolume got dynamically provisioned.

      kubectl get pvc

    注意: It can take up to a few minutes for the PVs to be provisioned and bound.

    The response should be like this:

      NAME             STATUS    VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS       AGE
      mysql-pv-claim   Bound     pvc-8cbd7b2e-4044-11e9-b2bb-42010a800002   20Gi       RWO            standard           77s
      wp-pv-claim      Bound     pvc-8cd0df54-4044-11e9-b2bb-42010a800002   20Gi       RWO            standard           77s
  3. Verify that the Pod is running by running the following command:

      kubectl get pods

    注意: It can take up to a few minutes for the Pod’s Status to be RUNNING.

    The response should be like this:

      NAME                               READY     STATUS    RESTARTS   AGE
      wordpress-mysql-1894417608-x5dzt   1/1       Running   0          40s
    
  4. Verify that the Service is running by running the following command:

      kubectl get services wordpress

    The response should be like this:

      NAME        TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)        AGE
      wordpress   ClusterIP   10.0.0.89    <pending>     80:32406/TCP   4m
    

    注意: Minikube can only expose Services through NodePort. The EXTERNAL-IP is always pending.

  5. Run the following command to get the IP Address for the WordPress Service:

      minikube service wordpress --url

    The response should be like this:

      http://1.2.3.4:32406
    
  6. Copy the IP address, and load the page in your browser to view your site.

You should see the WordPress set up page similar to the following screenshot.

wordpress-init

警告: Do not leave your WordPress installation on this page. If another user finds it, they can set up a website on your instance and use it to serve malicious content.

Either install WordPress by creating a username and password or delete your instance.

清理现场

  1. Run the following command to delete your Secret, Deployments, Services and PersistentVolumeClaims:

      kubectl delete -k ./

接下来

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