target
Create a PV in your environment
Create a Deployment for MySQl
Exposing MySQL to other pod s in the cluster by DNS name
Before the beginning
You need a Kubernetes cluster, a kubectl command-line tool that can connect to the cluster. If you don't have a cluster, you can use Minikube To create.
We will create a PV (Persistent Volume) for data storage. click here To see the types supported by PV, the guide will use GCEPersistentDisk to demonstrate, but in fact any PV type can work properly. GCE PersistentDisk works only on Google Compute Engine (GCE).
Create disks in your environment
In Google Compute Engine, run:
gcloud compute disks create --size=20GB mysql-disk
Then create a PV pointing to the mysql-disk you just created. Here is a configuration file for creating PV, pointing to the GCE disk mentioned above:
apiVersion: v1 kind: PersistentVolume metadata: name: mysql-pv spec: capacity: storage: 20Gi accessModes: - ReadWriteOnce gcePersistentDisk: pdName: mysql-disk fsType: ext4
Note that the line pdName: mysql-disk matches the name of the disk created by the GCE environment above. If you want to create PV s in other environments, you can view them Persistent Volumes To get detailed information.
Create PV:
kubectl create -f https://k8s.io/docs/tasks/run-application/gce-volume.yaml
Deployment of MySQL
You can create a stateful service through Kubernetes Deployment, and then use PVC (Persistent Volume Claim) to connect existing PVs. For example, the following YAML file describes a Deployment that runs MySQL and uses PVC. The file defines a mount to / var/lib/mysql volume and creates a 20G volume size PVC.
Note: The password is defined in the YAML configuration file, which is insecure. See Kubernetes Secrets Get a safer solution.
apiVersion: v1 kind: Service metadata: name: mysql spec: ports: - port: 3306 selector: app: mysql clusterIP: None --- apiVersion: v1 kind: PersistentVolumeClaim metadata: name: mysql-pv-claim spec: accessModes: - ReadWriteOnce resources: requests: storage: 20Gi --- apiVersion: apps/v1beta1 kind: Deployment metadata: name: mysql spec: strategy: type: Recreate template: metadata: labels: app: mysql spec: containers: - image: mysql:5.6 name: mysql env: # Use secret in real usage - name: MYSQL_ROOT_PASSWORD value: password ports: - containerPort: 3306 name: mysql volumeMounts: - name: mysql-persistent-storage mountPath: /var/lib/mysql volumes: - name: mysql-persistent-storage persistentVolumeClaim: claimName: mysql-pv-claim
1. Deploy the contents of the YAML file.
kubectl create -f https://k8s.io/docs/tasks/run-application/mysql-deployment.yaml
2. Display Deployment information.
kubectl describe deployment mysql Name: mysql Namespace: default CreationTimestamp: Tue, 01 Nov 2016 11:18:45 -0700 Labels: app=mysql Selector: app=mysql Replicas: 1 updated | 1 total | 0 available | 1 unavailable StrategyType: Recreate MinReadySeconds: 0 OldReplicaSets: <none> NewReplicaSet: mysql-63082529 (1/1 replicas created) Events: FirstSeen LastSeen Count From SubobjectPath Type Reason Message --------- -------- ----- ---- ------------- -------- ------ ------- 33s 33s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set mysql-63082529 to 1
3. Display the pod created by Deployment.
kubectl get pods -l app=mysql NAME READY STATUS RESTARTS AGE mysql-63082529-2z3ki 1/1 Running 0 3m
4. Check PV.
kubectl describe pv mysql-pv Name: mysql-pv Labels: <none> Status: Bound Claim: default/mysql-pv-claim Reclaim Policy: Retain Access Modes: RWO Capacity: 20Gi Message: Source: Type: GCEPersistentDisk (a Persistent Disk resource in Google Compute Engine) PDName: mysql-disk FSType: ext4 Partition: 0 ReadOnly: false No events.
5. Check PVC.
kubectl describe pvc mysql-pv-claim Name: mysql-pv-claim Namespace: default Status: Bound Volume: mysql-pv Labels: <none> Capacity: 20Gi Access Modes: RWO No events.
Visit MySQL instances
The previous YAML file creates a service that allows other Pods in the cluster to access the database. The service option cluster IP: None causes the DNS name of the service to be resolved directly to the IP address of Pod. When your service has only one Pod and you don't want to increase the number of Pods, this is the best way to use it.
Run a Mysql client to connect to the Mysql service:
kubectl run -it --rm --image=mysql:5.6 mysql-client -- mysql -h <pod-ip> -ppassword
The above command creates a new Pod in the cluster, which runs a MySQL client and connects to the Mysql Server of the above service. If it connects successfully, it means that the stateful MySQL database has been successfully started and run.
Waiting for pod default/mysql-client-274442439-zyp6i to be running, status is Pending, pod ready: false If you don't see a command prompt, try pressing enter. mysql>
To update
Updating Deployment's image or other parts can also be done using the kubectl application command as usual. Here are some things to note when using stateful applications:
- Do not expand the application. This application is only for single application. The following PV can only be mapped to one Pod. For stateful applications in clusters, see StatefulSet document.
- Use strategy: type: Recreate in Deployment's YAML configuration document. It tells Kubernetes not to use rolling update. Because Rolling update doesn't work, there won't be multiple Pods running at the same time. The policy Recreate deletes the previous pod when a new Pod is created using the update configuration.
Delete Deployment
Delete Deployment objects by name:
kubectl delete deployment,svc mysql kubectl delete pvc mysql-pv-claim kubectl delete pv mysql-pvIn addition, if you are using GCE disk, you need to delete the corresponding disk:
gcloud compute disks delete mysql-disk