$(POD_NAME) in subPath of Statefulset + Kustomize not expanding - kubernetes

Question

I have a stateful set with a volume that uses a subPath: $(POD_NAME) I've also tried $HOSTNAME which also doesn't work. How does one set the subPath of a volumeMount to the name of the pod or the $HOSTNAME?
Here's what I have:
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: ravendb
namespace: pltfrmd
labels:
app: ravendb
spec:
serviceName: ravendb
template:
metadata:
labels:
app: ravendb
spec:
containers:
- command:
# ["/bin/sh", "-ec", "while :; do echo '.'; sleep 6 ; done"]
- /bin/sh
- -c
- /opt/RavenDB/Server/Raven.Server --log-to-console --config-path /configuration/settings.json
image: ravendb/ravendb:latest
imagePullPolicy: Always
name: ravendb
env:
- name: POD_HOST_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: RAVEN_Logs_Mode
value: Information
ports:
- containerPort: 8080
name: http-api
protocol: TCP
- containerPort: 38888
name: tcp-server
protocol: TCP
- containerPort: 161
name: snmp
protocol: TCP
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /data
name: data
subPath: $(POD_NAME)
- mountPath: /configuration
name: configuration
subPath: ravendb
- mountPath: /certificates
name: certificates
dnsPolicy: ClusterFirst
restartPolicy: Always
terminationGracePeriodSeconds: 120
volumes:
- name: certificates
secret:
secretName: ravendb-certificate
- name: configuration
persistentVolumeClaim:
claimName: configuration
- name: data
persistentVolumeClaim:
claimName: ravendb
And the Persistent Volume:
apiVersion: v1
kind: PersistentVolume
metadata:
namespace: pltfrmd
name: ravendb
labels:
type: local
spec:
storageClassName: local-storage
capacity:
storage: 30Gi
accessModes:
- ReadWriteOnce
hostPath:
path: /volumes/ravendb
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
namespace: pltfrmd
name: ravendb
spec:
storageClassName: local-storage
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 30Gi
$HOSTNAME used to work, but doesn't anymore for some reason. Wondering if it's a bug in the host path storage provider?

Answer 1

apiVersion: v1
kind: Service
metadata:
name: nginx
labels:
app: nginx
spec:
ports:
- port: 80
targetPort: 80
selector:
app: nginx
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx
spec:
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.10
ports:
- containerPort: 80
volumeMounts:
- name: nginx
mountPath: /usr/share/nginx/html
subPath: $(POD_NAME)
volumes:
- name: nginx
configMap:
name: nginx

Answer 2

Ok, so after great experimentation I found a way that still works:
Step one, map an environment variable:
env:
- name: POD_HOST_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
This creates $(POD_HOST_NAME) based on the field metadata.name
Then in your mount you do this:
volumeMounts:
- mountPath: /data
name: data
subPathExpr: $(POD_HOST_NAME)
It's important to use subPathExpr as subPath (which worked before) doesn't work. Then it will use the environment variable you created and properly expand it.