NFS support for default storage

cluster/juju/layers/kubernetes-worker/layer.yaml

@@ -14,6 +14,7 @@ includes:
   - 'interface:kube-control'
   - 'interface:aws'
   - 'interface:gcp'
+  - 'interface:mount'
 config:
   deletes:
     - install_from_upstream

cluster/juju/layers/kubernetes-worker/metadata.yaml

@@ -7,6 +7,7 @@ maintainers:
   - Konstantinos Tsakalozos <kos.tsakalozos@canonical.com>
   - Charles Butler <Chuck@dasroot.net>
   - Matthew Bruzek <mbruzek@ubuntu.com>
+  - Mike Wilson <mike.wilson@canonical.com>
 description: |
   Kubernetes is an open-source platform for deploying, scaling, and operations
   of application containers across a cluster of hosts. Kubernetes is portable
@@ -32,6 +33,8 @@ requires:
     interface: aws
   gcp:
     interface: gcp
+  nfs:
+    interface: mount
 provides:
   cni:
     interface: kubernetes-cni

cluster/juju/layers/kubernetes-worker/reactive/kubernetes_worker.py

@@ -1174,3 +1174,65 @@ def _write_gcp_snap_config(component):
         daemon_env += '{}={}\n'.format(gcp_creds_env_key, creds_path)
         daemon_env_path.parent.mkdir(parents=True, exist_ok=True)
         daemon_env_path.write_text(daemon_env)
+
+
+def get_first_mount(mount_relation):
+    mount_relation_list = mount_relation.mounts()
+    if mount_relation_list and len(mount_relation_list) > 0:
+        # mount relation list is a list of the mount layer relations
+        # for now we just use the first one that is nfs
+        for mount in mount_relation_list:
+            # for now we just check the first mount and use that.
+            # the nfs charm only supports one for now.
+            if ('mounts' in mount and
+                    mount['mounts'][0]['fstype'] == 'nfs'):
+                return mount['mounts'][0]
+    return None
+
+
+@when('nfs.available')
+def nfs_state_control(mount):
+    ''' Determine if we should remove the state that controls the re-render
+    and execution of the nfs-relation-changed event because there
+    are changes in the relationship data, and we should re-render any
+    configs '''
+
+    mount_data = get_first_mount(mount)
+    if mount_data:
+        nfs_relation_data = {
+            'options': mount_data['options'],
+            'host': mount_data['hostname'],
+            'mountpoint': mount_data['mountpoint'],
+            'fstype': mount_data['fstype']
+        }
+
+        # Re-execute the rendering if the data has changed.
+        if data_changed('nfs-config', nfs_relation_data):
+            hookenv.log('reconfiguring nfs')
+            remove_state('nfs.configured')
+
+
+@when('nfs.available')
+@when_not('nfs.configured')
+def nfs_storage(mount):
+    '''NFS on kubernetes requires nfs config rendered into a deployment of
+    the nfs client provisioner. That will handle the persistent volume claims
+    with no persistent volume to back them.'''
+
+    mount_data = get_first_mount(mount)
+    if not mount_data:
+        return
+
+    addon_path = '/root/cdk/addons/{}'
+    # Render the NFS deployment
+    manifest = addon_path.format('nfs-provisioner.yaml')
+    render('nfs-provisioner.yaml', manifest, mount_data)
+    hookenv.log('Creating the nfs provisioner.')
+    try:
+        kubectl('apply', '-f', manifest)
+    except CalledProcessError as e:
+        hookenv.log(e)
+        hookenv.log('Failed to create nfs provisioner. Will attempt again next update.')  # noqa
+        return
+
+    set_state('nfs.configured')

cluster/juju/layers/kubernetes-worker/templates/nfs-provisioner.yaml

+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: default
+  annotations:
+    storageclass.kubernetes.io/is-default-class: "true"
+provisioner: fuseim.pri/ifs
+---
+kind: Deployment
+apiVersion: extensions/v1beta1
+metadata:
+  name: nfs-client-provisioner
+spec:
+  replicas: 1
+  strategy:
+    type: Recreate
+  template:
+    metadata:
+      labels:
+        app: nfs-client-provisioner
+    spec:
+      containers:
+        - name: nfs-client-provisioner
+          image: quay.io/external_storage/nfs-client-provisioner:latest
+          volumeMounts:
+            - name: nfs-client-root
+              mountPath: /persistentvolumes
+          env:
+            - name: PROVISIONER_NAME
+              value: fuseim.pri/ifs
+            - name: NFS_SERVER
+              value: {{ hostname }}
+            - name: NFS_PATH
+              value: {{ mountpoint }}
+      volumes:
+        - name: nfs-client-root
+          nfs:
+            server: {{ hostname }}
+            path: {{ mountpoint }}