Connecting Storage to StatefulSets

Create a PersistentVolume for the Postgres database.

1. Create a file called pv.yaml with the following content:

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   apiVersion: v1
   kind: PersistentVolume
   metadata:
     name: my-persistent-volume
   spec:
     storageClassName: default
     volumeMode: Filesystem
     capacity:
       storage: 10Gi
     accessModes:
       - ReadWriteOnce
     hostPath:
       path: "/mnt/data"

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2. Apply the file to the cluster:

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   kubectl apply -f pv.yaml

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3. Check if the PersistentVolume was created:

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   kubectl get pv my-persistent-volume

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   The PersistentVolume my-persistent-volume status should now be Available. Let's switch back to the role of a developer.

Create PersistentVolumeClaim for the Postgres database

1. Create a file called pvc.yaml with the following content:

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   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: postgres-claim
   spec:
     storageClassName: default
     accessModes:
       - ReadWriteOnce
     resources:
       requests:
         storage: 5Gi

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2. Apply the file to the cluster:

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   kubectl apply -f pvc.yaml

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3. Check if the PersistentVolumeClaim was created:

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   kubectl get pvc postgres-claim

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   The status of the PersistentVolumeClaim postgres-claim should now be Pending. This is because it is waiting for the first consumer to bind it. This first consumer will be created in the next task.

Create a StatefulSet for the Postgres database.

1. Create a new file called postgres.yaml and specify the StatefulSet to create a postgres database.

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   apiVersion: apps/v1
   kind: StatefulSet
   metadata:
     name: postgres
   spec:
     serviceName: postgres
     selector:
       matchLabels:
         app: postgres
     replicas: 1
     template:
       metadata:
         labels:
           app: postgres
       spec:
         containers: # This is the container that will run the postgres image
           - name: postgres
             image: postgres:15.1
             imagePullPolicy: "IfNotPresent"
             ports:
             - containerPort: 5432
             env: # Some environment variables to define a user
             - name: POSTGRES_DB
               value: "postgresdb"
             - name: POSTGRES_USER
               value: "admin"
             - name: POSTGRES_PASSWORD
               value: "password"
             volumeMounts: # mount a volume to the path where postgres will store data 
             - name: data
               mountPath: /var/lib/postgresql/data
         volumes: # This is the volume that will be mounted to the container
         - name: data
           persistentVolumeClaim:
             claimName: postgres-claim

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2. Apply the file to create the StatefulSet.

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   kubectl apply -f postgres.yaml

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3. Check if the StatefulSet was created.

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   kubectl get statefulset postgres

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4. Check if the Pod postgres-0 was created.

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   kubectl get pod postgres-0

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Verify that the PersistentVolumeClaim is bound.

1. Check if the PersistentVolumeClaim was bound to the PersistentVolume.

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   kubectl get pvc postgres-claim

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   It should now be in the status Bound.

   Note

   You can also play around with the postgres database. You can connect to it locally by port-forwarding the postgres-0 Pod to your local machine.

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   kubectl port-forward postgres-0 5432:5432

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   Note

   With the Postgres client of your choice, you can now connect to the database with the credentials specified in the postgres.yaml file.

   Insert data into the database, remove the pod, wait for it to be recreated and check if the data is still there.