Require relation to nova-compute application

Without a relation to at least one nova-compute application a
cinder-ceph backend will not be functional as the libvirt
secrets will not have been created to allow access to the
ceph cluster from libvirt/qemu.

Add a simple context to check that the 'ceph-access' relation
is present.  This will result in a blocked status if the
relation is not detected - for example:

  Missing relations: nova-compute

Change-Id: Iedbf4aafc2348cbf6f14257417e86aa9aeb48a81
Closes-Bug: 1718051

hooks/ceph-access-relation-broken

@@ -0,0 +1 @@
+cinder_hooks.py

hooks/ceph-access-relation-departed

@@ -0,0 +1 @@
+cinder_hooks.py

hooks/cinder_contexts.py

@@ -17,6 +17,8 @@ from charmhelpers.core.hookenv import (
     service_name,
     is_relation_made,
     leader_get,
+    relation_ids,
+    related_units,
 )
 
 from charmhelpers.contrib.openstack.context import (
@@ -35,6 +37,17 @@ def ceph_config_file():
     return CHARM_CEPH_CONF.format(service_name())
 
 
+class CephAccessContext(OSContextGenerator):
+    interfaces = ['ceph-access']
+
+    def __call__(self):
+        """Simple check to validate that compute units are present"""
+        for r_id in relation_ids(self.interfaces[0]):
+            if related_units(r_id):
+                return {'complete': True}
+        return {}
+
+
 class CephSubordinateContext(OSContextGenerator):
     interfaces = ['ceph-cinder']
 

hooks/cinder_utils.py

@@ -30,6 +30,8 @@ from charmhelpers.core.hookenv import (
 )
 from charmhelpers.core.host import mkdir
 
+import cinder_contexts
+
 
 PACKAGES = [
     'ceph-common',
@@ -39,6 +41,7 @@ VERSION_PACKAGE = 'cinder-common'
 
 REQUIRED_INTERFACES = {
     'ceph': ['ceph'],
+    'nova-compute': ['ceph-access'],
 }
 
 CHARM_CEPH_CONF = '/var/lib/charm/{}/ceph.conf'
@@ -84,7 +87,8 @@ def register_configs():
         install_alternative(os.path.basename(CEPH_CONF),
                             CEPH_CONF, ceph_config_file())
         CONFIG_FILES[ceph_config_file()] = {
-            'hook_contexts': [context.CephContext()],
+            'hook_contexts': [context.CephContext(),
+                              cinder_contexts.CephAccessContext()],
             'services': ['cinder-volume'],
         }
         confs.append(ceph_config_file())

test-requirements.txt

@@ -10,7 +10,7 @@
 charm-tools>=2.4.4
 requests>=2.18.4
 mock>=1.2
-flake8>=2.2.4,<=2.4.1
+flake8>=2.2.4
 stestr>=2.2.0
 coverage>=4.5.2
 pyudev              # for ceph-* charm unit tests (need to fix the ceph-* charm unit tests/mocking)

unit_tests/__init__.py

@@ -26,6 +26,7 @@ def _add_path(path):
     if path not in sys.path:
         sys.path.insert(1, path)
 
+
 _add_path(_actions)
 _add_path(_hooks)
 _add_path(_charmhelpers)

unit_tests/test_cinder_contexts.py

@@ -24,6 +24,8 @@ TO_PATCH = [
     'service_name',
     'get_os_codename_package',
     'leader_get',
+    'relation_ids',
+    'related_units',
 ]
 
 
@@ -140,3 +142,19 @@ class TestCinderContext(CharmTestCase):
                     }
                 }
             }})
+
+    def test_ceph_access_incomplete(self):
+        self.relation_ids.return_value = ['ceph-access:1']
+        self.related_units.return_value = []
+        self.assertEqual(
+            contexts.CephAccessContext()(),
+            {}
+        )
+
+    def test_ceph_access_complete(self):
+        self.relation_ids.return_value = ['ceph-access:1']
+        self.related_units.return_value = ['nova-compute/0', 'nova-compute/1']
+        self.assertEqual(
+            contexts.CephAccessContext()(),
+            {'complete': True}
+        )

unit_tests/test_utils.py

@@ -93,9 +93,9 @@ class TestConfig(object):
         return self.config
 
     def set(self, attr, value):
-            if attr not in self.config:
-                raise KeyError
-            self.config[attr] = value
+        if attr not in self.config:
+            raise KeyError
+        self.config[attr] = value
 
 
 class TestRelation(object):