How to make My Sql Pod to save data in Persistent Volume - mysql

Question

I started to use Kubernetes to understant concepts like pods, objects and so on. I started to learn about Persistent Volume and Persistent Volume Claim, from my understanding, if i save data from mysql pod to a persistent volume, the data is saved no matter if i delete the mysql pod, the data is saved on the volume, but i don't think it works in my case...
I have a spring boot pod where i save data in mysql pod, data is saved, i can retreived, but when i restart my pods, delete or replace them, that saved data is lost, so i think i messed up something, can you give me a hint, please? Thanks...
Bellow are my Kubernetes files:
Mysql pod:
apiVersion: apps/v1
kind: Deployment
metadata:
name: mysql
labels:
app: mysql
spec:
selector:
matchLabels:
app: mysql
strategy:
type: Recreate
template:
metadata:
labels: #must match Service and DeploymentLabels
app: mysql
spec:
containers:
- image: mysql:5.7
args:
- "--ignore-db-dir=lost+found"
name: mysql #name of the db
env:
- name: MYSQL_ROOT_PASSWORD
valueFrom:
secretKeyRef:
name: db-secret #name of the secret obj
key: password #which value from inside the secret to take
- name: MYSQL_ROOT_USER
valueFrom:
secretKeyRef:
name: db-secret
key: username
- name: MYSQL_DATABASE
valueFrom:
configMapKeyRef:
name: db-config
key: name
ports:
- containerPort: 3306
name: mysql
volumeMounts: #mount volume obtained from PVC
- name: mysql-persistent-storage
mountPath: /var/lib/mysql #mounting in the container will be here
volumes:
- name: mysql-persistent-storage #obtaining volume from PVC
persistentVolumeClaim:
claimName: mysql-pv-claim # can use the same claim in different pods
apiVersion: v1
kind: Service
metadata:
name: mysql #DNS name
labels:
app: mysql
spec:
ports:
- port: 3306
targetPort: 3306
selector: #mysql pod should contain same label
app: mysql
clusterIP: None # we use DNS
Persistent Volume and Persistent Volume Claim files:
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: mysql-pv-claim #name of our pvc
labels:
app: mysql
spec:
volumeName: host-pv #claim that volume created with this name
accessModes:
- ReadWriteOnce
storageClassName: standard
resources:
requests:
storage: 1Gi
apiVersion: v1 #version of our PV
kind: PersistentVolume #kind of obj we gonna create
metadata:
name: host-pv # name of our PV
spec: #spec of our PV
capacity: #size
storage: 4Gi
volumeMode: Filesystem #storage Type, File and Blcok
storageClassName: standard
accessModes:
- ReadWriteOnce # can be mount from multiple pods on a single nod, cam be use by multiple pods, multiple pods can use this pv but only from a single node
# - ReadOnlyMany # on multiple nodes
# - WriteOnlyMany # doar pt multiple nods, nu hostPath type
hostPath: #which type of pv
path: "/mnt/data"
type: DirectoryOrCreate
persistentVolumeReclaimPolicy: Retain
My Spring book K8 file:
apiVersion: v1
kind: Service
metadata:
name: book-service
spec:
selector:
app: book-example
ports:
- protocol: 'TCP'
port: 8080
targetPort: 8080
type: LoadBalancer
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: book-deployment
spec:
replicas: 1
selector:
matchLabels:
app: book-example
template:
metadata:
labels:
app: book-example
spec:
containers:
- name: book-container
image: cinevacineva/kubernetes_book_pv:latest
imagePullPolicy: Always
# ports:
# - containerPort: 8080
env:
- name: DB_HOST
valueFrom:
configMapKeyRef:
name: db-config
key: host
- name: DB_NAME
valueFrom:
configMapKeyRef:
name: db-config
key: name
- name: DB_USERNAME
valueFrom:
secretKeyRef:
name: db-user
key: username
- name: DB_PASSWORD
valueFrom:
secretKeyRef:
name: db-user
key: password
# & minikube -p minikube docker-env | Invoke-Expression links docker images we create with minikube, nu mai trebe sa ppusham

Answer 1

...if i save data from mysql pod to a persistent volume, the data is saved no matter if i delete the mysql pod, the data is saved on the volume, but i don't think it works in my case...
Your previous data will not be available when the pod switch node. To use hostPath you don't really need PVC/PV. Try:
apiVersion: apps/v1
kind: Deployment
metadata:
name: mysql
...
spec:
...
template:
...
spec:
...
nodeSelector: # <-- make sure your pod runs on the same node
<node label>: <value unique to the mysql node>
volumes: # <-- mount the data path on the node, no pvc/pv required.
- name: mysql-persistent-storage
hostPath:
path: /mnt/data
type: DirectoryOrCreate
containers:
- name: mysql
...
volumeMounts: # <-- let mysql write to it
- name: mysql-persistent-storage
mountPath: /var/lib/mysql