In this step, we will create a Portworx volume (PVC) for mysql.

Step: Create StorageClass and PersistentVolumeClaim

Create the storage class using:

kubectl create -f px-repl3-sc.yaml

Create the PersistentVolumeClaim using:

kubectl create -f px-mysql-pvc.yaml

Now that we have the volumes created, let's deploy mysql !

In this step, we will deploy the mysql application using the PersistentVolumeClaim created before.

Step: Create secret for mysql

Below we are creating a Secret to store the mysql password.

echo mysql123 > password.txt
tr --delete '\n' <password.txt >.strippedpassword.txt && mv .strippedpassword.txt password.txt
kubectl create secret generic mysql-pass --from-file=password.txt

Step: Create secret for mysql

Below we will create a mysql Deployment that uses a Portworx PVC.

kubectl create -f mysql-app.yaml

Feel free to cat mysql-app.yaml and observe the volumeMounts and volumes sections where we mount the PVC.

Step: Verify mysql pod is ready

Below commands wait till the mysql pods are in ready state.

while true; do
    NUM_READY=`kubectl get pods -l app=mysql -o wide | grep Running | grep 1/1 | wc -l`
    if [ "${NUM_READY}" == "1" ]; then
        echo "mysql is ready !"
        break
    else
        echo "Waiting for mysql to be ready..."
        kubectl get pods -l app=mysql -o wide
    fi
    sleep 5
done

In this step, we will use pxctl to inspect the volume

Step: Inspect the Portworx volume

Portworx ships with a pxctl command line that can be used to manage Portworx.

Below we will use pxctl to inspect the underlying volume for our PVC.

VOL=`kubectl get pvc | grep px-mysql-pvc | awk '{print $3}'`
PX_POD=$(kubectl get pods -l name=portworx -n kube-system -o jsonpath='{.items[0].metadata.name}')
kubectl exec -it $PX_POD -n kube-system -- /opt/pwx/bin/pxctl volume inspect ${VOL}

Make the following observations in the inspect output

• State indicates the volume is attached and shows the node on which it is attached. This is the node where the Kubernetes pod is running.
• HA shows the number of configured replcas for this volume
• Labels show the name of the PVC for this volume
• Replica sets on nodes shows the px nodes on which volume is replicated

Now that we have mysql up, let's proceed to creating a sample database!

In this step, we will initialize a sample database in our mysql instance.

Step: Initialize a sample db

Below commands exec into the mysql pod and create a sample database.

POD=`kubectl get pods -l app=mysql | grep Running | grep 1/1 | awk '{print $1}'`
kubectl exec -it $POD bash

mysql --user=root --password=mysql123
create database pxdemo;
use pxdemo;
create table grapevine (counter int unsigned);
show tables;
quit;

In this step, we will simulate failure of an application by deleting the mysql pod.

Step: Delete the mysql pod

Below commands get the name of the running mysql pod and delete it.

POD_TO_DELETE=`kubectl get pods -l app=mysql -o wide | grep -v NAME | awk '{print $1}'`

echo "Deleting mysql pod: ${POD_TO_DELETE}"

kubectl delete pod ${POD_TO_DELETE}

Once the mysql pod gets deleted, Kubernetes will start to create a new mysql pod on another node.

Step: Verify replacement pod starts running

Below commands wait till the new mysql pod is ready.

kubectl get pods -l app=mysql -o wide

while true; do
    NUM_READY=`kubectl get pods -l app=mysql -o wide | grep Running | grep 1/1 | wc -l`
    if [ "${NUM_READY}" == "1" ]; then
        echo "mysql is ready !"
        break
    else
        echo "Waiting for mysql to be ready..."
        kubectl get pods -l app=mysql -o wide
    fi
    sleep 5
done

Now that we have the new mysql pod running, let's check if the database we previously created is still intact.

In this step, we will check the state of our sample mysql database.

Step: Verify data

Below commands exec into the running mysql pod and dump our sample database.

POD=`kubectl get pods -l app=mysql | grep Running | grep 1/1 | awk '{print $1}'`
kubectl exec -it $POD bash

mysql --user=root --password=mysql123
show databases;
use pxdemo;
show tables;
quit;

Observe that the database table is persisted !