Add support for rolling back snapshots

We supported creating snapshots, but not doing anything with them. This
removes the manual task of restoring a snapshot and replace it with a
PVC abstraction of rolling back to a snapshot.

While Ceph recommends cloning a snapshot instead of rolling back, due to
the time taken, in our usecase I don't think that is an optimal
strategy, as it will leave dangling clones that we'd then have to
manage.

Closes #183

api-daemon/pvcapid/flaskapi.py

@@ -6362,6 +6362,59 @@ api.add_resource(
 )
 
 
+# /storage/ceph/snapshot/<pool>/<volume>/<snapshot>/rollback
+class API_Storage_Ceph_Snapshot_Rollback_Element(Resource):
+    @Authenticator
+    def post(self, pool, volume, snapshot):
+        """
+        Roll back an RBD volume {volume} in pool {pool} to snapshot {snapshot}
+
+        WARNING: This action cannot be done on an active RBD volume. All IO MUST be stopped first.
+        ---
+        tags:
+          - storage / ceph
+        parameters:
+          - in: query
+            name: snapshot
+            type: string
+            required: true
+            description: The name of the snapshot
+          - in: query
+            name: volume
+            type: string
+            required: true
+            description: The name of the volume
+          - in: query
+            name: pool
+            type: integer
+            required: true
+            description: The name of the pool
+        responses:
+          200:
+            description: OK
+            schema:
+              type: object
+              id: Message
+          404:
+            description: Not found
+            schema:
+              type: object
+              id: Message
+          400:
+            description: Bad request
+            schema:
+              type: object
+              id: Message
+        """
+        return api_helper.ceph_volume_snapshot_rollback(pool, volume, snapshot)
+
+
+api.add_resource(
+    API_Storage_Ceph_Snapshot_Rollback_Element,
+    "/storage/ceph/snapshot/<pool>/<volume>/<snapshot>/rollback",
+)
+
+
 ##########################################################
 # Provisioner API
 ##########################################################

api-daemon/pvcapid/helper.py

@@ -2183,6 +2183,22 @@ def ceph_volume_snapshot_rename(zkhandler, pool, volume, name, new_name):
     return output, retcode
 
 
+@ZKConnection(config)
+def ceph_volume_snapshot_rollback(zkhandler, pool, volume, name):
+    """
+    Roll back a Ceph RBD volume to a given snapshot in the PVC Ceph storage cluster.
+    """
+    retflag, retdata = pvc_ceph.rollback_snapshot(zkhandler, pool, volume, name)
+
+    if retflag:
+        retcode = 200
+    else:
+        retcode = 400
+
+    output = {"message": retdata.replace('"', "'")}
+    return output, retcode
+
+
 @ZKConnection(config)
 def ceph_volume_snapshot_remove(zkhandler, pool, volume, name):
     """