Validate node groups without volumes

MapR FS requires at least 1 separate partition or drive
to be deployed successfully. Hence, if there are neither
Cinder volumes nor ephemeral drive appended, cluster has
to be considered invalid

Change-Id: I9fac12be36b2e1f002db40cfdceecd662b7e7ee3
Closes-Bug: #1439433

doc/source/userdoc/mapr_plugin.rst

@@ -72,6 +72,7 @@ Every MapR cluster must contain:
 * exactly 1 *Webserver* process
 * odd number of *ZooKeeper* processes but not less than 1
 * *FileServer* process on every node
+* at least 1 Cinder volume or ephemeral drive per instance
 
 Every Hadoop cluster must contain exactly 1 *Oozie* process
 

sahara/plugins/mapr/services/maprfs/maprfs.py

@@ -78,6 +78,7 @@ class MapRFS(s.Service):
             vu.at_least(1, CLDB),
             vu.each_node_has(FILE_SERVER),
             vu.on_same_node(CLDB, FILE_SERVER),
+            vu.has_volumes(),
         ]
 
     def service_dir(self, cluster_context):

sahara/plugins/mapr/util/validation_utils.py

@@ -19,6 +19,7 @@ from sahara.conductor import resource as r
 import sahara.exceptions as ex
 from sahara.i18n import _
 import sahara.plugins.exceptions as e
+import sahara.utils.openstack.nova as nova
 
 
 class LessThanCountException(e.InvalidComponentCountException):
@@ -78,6 +79,16 @@ class NodeServiceConflictException(ex.SaharaException):
         self.code = NodeServiceConflictException.ERROR_CODE
 
 
+class NoVolumesException(ex.SaharaException):
+    MESSAGE = _('%s must have at least 1 volume or ephemeral drive')
+    ERROR_CODE = "NO_VOLUMES"
+
+    def __init__(self, ng_name):
+        super(NoVolumesException, self).__init__()
+        self.message = NoVolumesException.MESSAGE % ng_name
+        self.code = NoVolumesException.ERROR_CODE
+
+
 def at_least(count, component):
     def validate(cluster_context, component, count):
         actual_count = cluster_context.get_instances_count(component)
@@ -173,3 +184,16 @@ def create_fake_cluster(cluster, existing, additional):
     cluster_dict.update({'node_groups': updated + not_updated})
     fake = r.ClusterResource(cluster_dict)
     return fake
+
+
+def get_ephemeral(node_group):
+    return nova.get_flavor(id=node_group.flavor_id).ephemeral
+
+
+def has_volumes():
+    def validate(cluster_context):
+        for node_group in cluster_context.cluster.node_groups:
+            if not (node_group.volumes_per_node or get_ephemeral(node_group)):
+                raise NoVolumesException(node_group.name)
+
+    return validate