Kubernetes Deployment populates wrong Persistent Volume - docker

Question

I'm trying to create two deployments, one for Wordpress the other for MySQL which refer to two different Persistent Volumes.
Sometimes, while deleting and recreating volumes and deployments, the MySQL deployment populates the Wordpress volume (ending up with a database in the wordpress-volume directory).
This is clearer when you do kubectl get pv --namespace my-namespace:
mysql-volume 2Gi RWO Retain Bound flashart-it/wordpress-volume-claim manual 1h
wordpress-volume 2Gi RWO Retain Bound flashart-it/mysql-volume-claim manual
.
I'm pretty sure the settings are ok. Please find the yaml file below.
Persistent Volume Claims + Persistent Volumes
kind: PersistentVolume
apiVersion: v1
metadata:
namespace: my-namespace
name: mysql-volume
labels:
type: local
spec:
storageClassName: manual
capacity:
storage: 2Gi
accessModes:
- ReadWriteOnce
hostPath:
path: /path/to/mount/mysql-volume
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
namespace: my-namespace
name: mysql-volume-claim
spec:
storageClassName: manual
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gi
---
kind: PersistentVolume
apiVersion: v1
metadata:
namespace: my-namespace
name: wordpress-volume
labels:
type: local
spec:
storageClassName: manual
capacity:
storage: 2Gi
accessModes:
- ReadWriteOnce
hostPath:
path: /path/to/mount/wordpress-volume
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
namespace: my-namespace
name: wordpress-volume-claim
spec:
storageClassName: manual
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gi
Deployments
kind: Deployment
apiVersion: apps/v1
metadata:
name: wordpress
namespace: my-namespace
labels:
app: wordpress
spec:
selector:
matchLabels:
app: wordpress
tier: frontend
strategy:
type: Recreate
template:
metadata:
namespace: my-namespace
labels:
app: wordpress
tier: frontend
spec:
containers:
- image: wordpress:5.0-php7.1-apache
name: wordpress
env:
# ...
ports:
# ...
volumeMounts:
- name: wordpress-volume
mountPath: /var/www/html
volumes:
- name: wordpress-volume
persistentVolumeClaim:
claimName: wordpress-volume-claim
---
kind: Deployment
apiVersion: apps/v1
metadata:
namespace: my-namespace
name: wordpress-mysql
labels:
app: wordpress
spec:
selector:
matchLabels:
app: wordpress
tier: mysql
strategy:
type: Recreate
template:
metadata:
namespace: my-namespace
labels:
app: wordpress
tier: mysql
spec:
containers:
- image: mysql:5.7
name: mysql
env:
# ...
ports:
# ...
volumeMounts:
- name: mysql-volume
mountPath: /var/lib/mysql
volumes:
- name: mysql-volume
persistentVolumeClaim:
claimName: mysql-volume-claim

Answer 1

It's expected behavior in Kubernetes. PVC can bind to any available PV, given that storage class is matched, access mode is matched, and storage size is sufficient. Names are not used to match PVC and PV.
A possible solution for your scenario is to use label selector on PVC to filter qualified PV.
First, add a label to PV (in this case: app=mysql)
kind: PersistentVolume
apiVersion: v1
metadata:
name: mysql-volume
labels:
app: mysql
Then, add a label selector in PVC to filter PV.
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
namespace: my-namespace
name: mysql-volume-claim
spec:
storageClassName: manual
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gi
selector:
matchLabels:
app: mysql