MySql databases deleted on new deployment in kubernetes

Question

I have created MySql container in kubernetes Pod by using YAML deployment file. I am able to execute the mysql queries on that container and created few databases and tables with data in it. But when I make some changes in other code of project not related to kubernetes files and deployed it. On the recreation of pod all my previous databases are deleted from MySql container. I have also given mount path to mount the PVC to my container.

So my question is how to store the databases permanently so that on recreation of pod it will not delete the database and able to access that databases through newly created pod

Answer 1

Is PVC mounted on the MySQL data directory like /var/libe/mysql or If you are having different data directory, Use appropriate mount path for PVC where mysql stores data. You can find the sample spec for mysql deployment here

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 k8s versions before 1.9.0 use apps/v1beta2  and before 1.8.0 use extensions/v1beta1
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
        livenessProbe:
          tcpSocket:
            port: 3306
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim
    ```

Answer 2

It's always best practice to run the single container inside the single POD.

You have to use the PVC and PV to store the data so that data get persistent even if the POD restarts or we update the YAML change to POD definition.

For example here for MySQL database

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - image: mysql:5.6
        name: mysql
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: 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

Ref : https://kubernetes.io/docs/tasks/run-application/run-single-instance-stateful-application/