K8S + HELM. Create a persistence volume for mysql database

Question

I am using K8S with Helm 3.

I am also using MYSQL 5.7 database.

How can I create MYSQL pod, that the database will persist (created on first time) after first time the pod is created, and even the pod is down and up again, the data won't be lost?

I am using PersistentVolume and PersistentVolumeClaim.

Here are the YAML files:

Mysql pod:

apiVersion: v1
kind: Pod
metadata:
  name: myproject-db
  namespace: {{ .Release.Namespace }}
  labels:
    name: myproject-db
    app: myproject-db
spec:
  hostname: myproject-db
  subdomain: {{ include "k8s.db.subdomain" . }}
  containers:
    - name: myproject-db
      image: mysql:5.7
      imagePullPolicy: IfNotPresent
      env:
        MYSQL_DATABASE: test
        MYSQL_ROOT_PASSWORD: 12345
      ports:
        - name: mysql
          protocol: TCP
          containerPort: 3306
      resources: 
        requests: 
          cpu: 200m
          memory: 500Mi
        limits:
          cpu: 500m
          memory: 600Mi
      volumeMounts:
        - name: mysql-persistence-storage
          mountPath: /var/lib/mysql
  volumes:
    - name: mysql-persistence-storage
      persistentVolumeClaim:
        claimName: mysql-pvc

Persistent Volume:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-pv
  labels:
    type: local
    name: mysql-pv
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/data/mysql"

Persistent Volume Claim:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  volumeMode: Filesystem
  volumeName: mysql-pv

Also, created a storage class. It is not used, but here it is:

Storage Class:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: mysql-storage
provisioner: docker.io/hostpath
volumeBindingMode: WaitForFirstConsumer

after running:

Helm install myproject myproject/

The database is created, and can be used.

If I add records and stop and remove the database pod, I would like that the records will be kepts - no loss of db.

Instead, I see that the db data is lost when the MYSQL pod is restarted.

What can I do in order to use helm install ... or helm upgrade (it is important that the pod created by helm command) and only after first time it will create the database, and for the next times the database data won't be lost?

Thanks.

Answer 1

It seems that you are using the host file system for the persistent volume. Assuming that you have multiple worker nodes and the pod restarts on a different node, the data is “lost” (only exists in the node that it ran on previously).

Force the pod to run on 1 particular node and restart the pod. You’ll notice that the data is still there as it restarts on the same node as before.