Persistent Payara Server Admin UI in Kubernetes - kubernetes

Question

I am using payara/server-full in Kubernetes. I want to add a persistent volume so that all configuration made to the Payara server via the Admin UI is perstisted after the pod is recreated, including uploaded .war files.
Right now my deployment looks like this:
apiVersion: apps/v1
kind: Deployment
metadata:
name:
spec:
selector:
matchLabels:
app: myapp
replicas: 3
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
maxSurge: 1
template:
metadata:
labels:
app: myapp
spec:
containers:
- name: myapp
image: payara/server-full
imagePullPolicy: "Always"
ports:
- name: myapp-default
containerPort: 8080
- name: myapp-admin
containerPort: 4848
How to augment that yaml file to make use of a persistent volume?
Which path(s) within payara should be synced with the persistent volume so that Payara's configuration isn't lost after redeployment ?
Which additional yaml files do I need?

Answer 1

So after a longer conideration of the problem I realised I need to persist everything under /opt/payara/appserver/glassfish/domains for all configuration made via the Admin UI to be persisted. However if I simply start the pod with a volumeMount pointing to that path, i.e.
apiVersion: apps/v1
kind: Deployment
metadata:
name: myapp
spec:
selector:
matchLabels:
app: myapp
replicas: 3
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
maxSurge: 1
template:
metadata:
labels:
app: myapp
spec:
volumes:
- name: myapp-vol
persistentVolumeClaim:
claimName: myapp-rwo-pvc
containers:
- name: myapp
image: payara/server-full
imagePullPolicy: "Always"
ports:
- name: myapp-default
containerPort: 8080
- name: myapp-admin
containerPort: 4848
volumeMounts:
- mountPath: "/opt/payara/appserver/glassfish/domains"
and
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: myapp-rwo-pvc
labels:
app: dont-delete-autom
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 3Gi
then the Payara server won't be able to start successfully, because Kubernetes will mount an empty persistent volume into that location. Payara needs however config files which are originally located within /opt/payara/appserver/glassfish/domains.
What I needed to do is to provision the volume with the data by default located in that folder. But how to do that when the only way to access the PV is to mount it into a pod?
Fist I scaled the above deployment to 0 with:
kubectl scale --replicas=0 deployment/myapp
This deletes all pods accessing the persistent volume.
Then I created a "provisioning" pod which mounts the previously created persistent volume into /tmp.
apiVersion: v1
kind: Pod
metadata:
labels:
app: myapp
name: pv-provisioner
namespace: default
spec:
containers:
- image: payara/server-full
imagePullPolicy: Always
name: pv-provisioner
ports:
- containerPort: 8080
name: myapp-default
protocol: TCP
- containerPort: 4848
name: myapp-admin
protocol: TCP
volumeMounts:
- mountPath: "/tmp"
name: myapp-vol
resources:
limits:
cpu: "2"
memory: 2Gi
requests:
cpu: 500m
memory: 128Mi
volumes:
- name: myapp-vol
persistentVolumeClaim:
claimName: myapp-rwo-pvc
Then I used the following commands to copy the necessary data first from the "provisioning" pod to a local folder /tmp and then back from /tmp to the persistent volume (previously mounted into pv-provisioner:/tmp). There is no option to copy directly from pod:/a to pod:/b
kubectl cp pv-provisioner:/opt/payara/appserver/glassfish/domains/. tmp
kubectl cp tmp/. pv-provisioner:/tmp
As a result everything stored under /opt/payara/appserver/glassfish/domains/ in the original payara container was now copied into the persistent volume identified by the persistence volume claim "myapp-rwo-pvc".
To finish it up I deleted the provisioning pod and scaled the deployment back up:
kubectl delete pod pv-provisioner
kubectl scale --replicas=3 deployment/myapp
The payara server is now starting successfully and any configuration made via the Admin UI, including .war deployments is persisted, such that the payara pods can be killed any time and after the restart everything is as before.
Thanks for reading.