ch05s04 - Red Hat OpenShift Administration I: Operating a Production Cluster

Guided Exercise: Provision Persistent Data Volumes

Deploy a MySQL database with persistent storage from a PVC and identify the PV and storage provisioner that backs the application.

Outcomes

You should be able to do the following tasks:

Deploy a MySQL database with persistent storage from a PVC.
Identify the PV that backs the application.
Identify the storage provisioner that created the PV.

As the student user on the workstation machine, use the lab command to prepare your system for this exercise.

This command ensures that all resources are available for this exercise.

[student@workstation ~]$ lab start storage-volumes

Instructions

Log in to the OpenShift cluster as the developer user with the developer password. Select the storage-volumes project.
1. Use a web browser to navigate to the OpenShift web console at https://console-openshift-console.apps.ocp4.example.com.
2. Log in by using Red Hat Identity Management with the developer username and the developer password.
3. Select the Administrator view to access the administrative menu.
4. On the Home → Projects page, select the storage-volumes project.
Identify the default storage class for the cluster.
1. Select the Storage → StorageClasses menu option.
  Figure 5.18: Storage classes
  The nfs-storage storage class has the Default label.
Use the registry.ocp4.example.com:8443/rhel8/mysql-80 container image to create a MySQL deployment named db-pod. Use the storage-volumes project. Add a service for the database.
1. Select the Workloads → Deployments menu option.
2. Verify that the storage-volumes project is active and select the Create Deployment button.
3. Use db-pod for the deployment name and change the image name to registry.ocp4.example.com:8443/rhel8/mysql-80.
4. Add the environment variables.
  Table 5.5. MYSQL Environment Variables
  Name Value
  MYSQL_USER user1
  MYSQL_PASSWORD mypa55w0rd
  MYSQL_DATABASE items
5. Select the Advanced options → Scaling link and set the replicas to one.
6. Click Create. Wait for the blue circle to indicate that a single pod is running.
7. Click Networking → Services → Create Service.
8. Add the service values.
  Table 5.6. Service Fields
  Field name Value
  Name db-pod
  selector app=db-pod
  Port 3306
  Target port 3306
  
  Figure 5.19: Add Service
9. Click the Create button.
Add a 1 Gi, RWO PVC named db-pod-pvc to the deployment. Set the /var/lib/mysql directory as the mount path.
1. Select the Workloads → Deployments menu item.
2. Click the three vertical dots in the row with the db-pod deployment, and select Add storage option.
3. In the Add Storage form, click Create new claim.
4. Add the following field values to the form.
  Table 5.7. Add PVC Storage Fields
  Field name Value
  PersistentVolumeClaim name db-pod-pvc
  Access mode RWO
  Size 1 GiB
  Volume mode Filesystem
  Mount path /var/lib/mysql
5. Click Save.
6. Scroll down in the deployment details to the Volumes section.
7. Select the db-pod-pvc link to see the PVC details.
  Figure 5.20: PVC Link

Name	Value
MYSQL_USER	user1
MYSQL_PASSWORD	mypa55w0rd
MYSQL_DATABASE	items

Field name	Value
Name	db-pod
selector	app=db-pod
Port	3306
Target port	3306

Field name	Value
PersistentVolumeClaim name	db-pod-pvc
Access mode	RWO
Size	1 GiB
Volume mode	Filesystem
Mount path	/var/lib/mysql

Observe how the volume mount changed the deployment.

Select the Workloads → Deployments → dp-pod → YAML tab.

Observe the volumes and volumeMounts additions to the deployment.

apiVersion: apps/v1
kind: Deployment

...output omitted...

      volumes:
      - name: db-pod-pvc
        persistentVolumeClaim:
          claimName: db-pod-pvc

...output omitted...

        volumeMounts:
        - mountPath: /var/lib/mysql
          name: db-pod-pvc

...output omitted...

Use a configuration map resource to add initialization data to the database.

Observe the contents of the init-db.sql script that initializes the database.

[student@workstation ~]$ cat \
~/DO180/labs/storage-volumes/configmap/init-db.sql

 DROP TABLE IF EXISTS `Item`;
 CREATE TABLE `Item` (`id` BIGINT not null auto_increment primary key, `description` VARCHAR(100), `done` BIT);
 INSERT INTO `Item` (`id`,`description`,`done`) VALUES (1,'Pick up newspaper', 0);
 INSERT INTO `Item` (`id`,`description`,`done`) VALUES (2,'Buy groceries', 1);

[student@workstation ~]$ oc login -u developer -p developer \
  https://api.ocp4.example.com:6443
Login successful.
...output omitted...

Set the storage-volumes project as the active project.

[student@workstation ~]$ oc project storage-volumes
...output omitted...

Use the contents of the init-db.sql file to create a configuration map named init-db-cm.

[student@workstation ~]$ oc create configmap init-db-cm \
--from-file=/home/student/DO180/labs/storage-volumes/configmap/init-db.sql
configmap/init-db-cm created

Add the init-db-cm configuration map resource as a volume named init-db-volume to the deployment. Specify the volume type as configmap, and set the /var/db/config directory as the mount path.

[student@workstation ~]$ oc set volumes deployment/db-pod \
--add --name init-db-volume --type configmap --configmap-name init-db-cm \
--mount-path /var/db/config
deployment.apps/db-pod volume updated

Start a remote shell session inside the container.

[student@workstation ~]$ oc rsh deployment/db-pod
sh-4.4$

Use the mysql client to execute the database script in the /var/db/config/init-db volume.

sh-4.4$ mysql -uuser1 -pmypa55w0rd items </var/db/config/init-db.sql
mysql: [Warning] Using a password on the command line interface can be insecure.
sh-4.4$

Execute a query to verify the database contents.

sh-4.4$ mysql -uuser1 -pmypa55w0rd items -e 'select * from Item;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+----+-------------------+------------+
| id | description       | done       |
+----+-------------------+------------+
|  1 | Pick up newspaper | 0x00       |
|  2 | Buy groceries     | 0x01       |
+----+-------------------+------------+
sh-4.4$

Exit the shell session.
```
sh-4.4$ exit
```

Delete and then re-create the db-pod deployment.

Delete the db-pod deployment.

[student@workstation ~]$ oc delete deployment/db-pod
deployment.apps "db-pod" deleted

Verify that the PVC still exists without the deployment.

[student@workstation ~]$ oc get pvc
NAME         STATUS   VOLUME                                     CAPACITY   ...
db-pod-pvc   Bound    pvc-ab5b38c7-359a-4e99-b81c-f7d11ef91cc9   1Gi        ...

Re-create the db-pod deployment.

[student@workstation ~]$ oc create deployment db-pod --port 3306 \
  --image=registry.ocp4.example.com:8443/rhel8/mysql-80
deployment.apps/db-pod created

Add the environment variables.

[student@workstation ~]$ oc set env deployment/db-pod \
  MYSQL_USER=user1 \
  MYSQL_PASSWORD=mypa55w0rd \
  MYSQL_DATABASE=items
deployment.apps/db-pod updated

Use the oc set volume command to attach the existing PVC to the deployment.

[student@workstation ~]$ oc set volumes deployment/db-pod \
  --add --type pvc \
  --mount-path /var/lib/mysql \
  --name db-pod-vol \
  --claim-name db-pod-pvc
deployment.apps/db-pod volume updated

Create a query-db pod by using the oc run command and the registry.ocp4.example.com:8443/redhattraining/do180-dbinit container image. Use the pod to execute a query against the database service.

Create the query-db pod. Configure the pod to use the MySQL client to execute a query against the db-pod service.

[student@workstation ~]$ oc run query-db -it --rm \
  --image registry.ocp4.example.com:8443/redhattraining/do180-dbinit \
  --restart Never \
  -- /bin/bash -c "mysql -uuser1 -pmypa55w0rd --protocol tcp \
  -h db-pod -P3306 items -e 'select * from Item;'"
mysql: [Warning] Using a password on the command line interface can be insecure.
+----+-------------------+------------+
| id | description       | done       |
+----+-------------------+------------+
|  1 | Pick up newspaper | 0x00       |
|  2 | Buy groceries     | 0x01       |
+----+-------------------+------------+
pod "query-db" deleted

Delete the db-pod deployment and the db-pod-pvc PVC.

Delete the db-pod deployment.

[student@workstation ~]$ oc delete deployment/db-pod
deployment.apps "db-pod" deleted

Delete the db-pod-pvc PVC.

[student@workstation ~]$ oc delete pvc/db-pod-pvc
persistentvolumeclaim "db-pod-pvc" deleted

Finish

On the workstation machine, use the lab command to complete this exercise. This step is important to ensure that resources from previous exercises do not impact upcoming exercises.

[student@workstation ~]$ lab finish storage-volumes