Merge "Dell PowerMax: RDF consistency exempt"

cinder/tests/unit/volume/drivers/dell_emc/powermax/test_powermax_rest.py

@@ -2085,12 +2085,14 @@ class PowerMaxRestTest(test.TestCase):
         rdf_group_no = self.data.rdf_group_no_1
         sg_name = self.data.default_sg_re_enabled
         rep_extra_specs = self.data.rep_extra_specs
-
         self.rest.srdf_suspend_replication(
             array_id, sg_name, rdf_group_no, rep_extra_specs)
+        # Replication mode in this test is synchronous, so the expecation
+        # is that the consistency exempt flag is false.
         mck_modify.assert_called_once_with(
             array_id, rdf_group_no, sg_name,
-            {'suspend': {'force': 'true'}, 'action': 'Suspend'},
+            {'suspend': {'force': 'true', 'consExempt': 'false'},
+             'action': 'Suspend'},
             rep_extra_specs, 'Suspend SRDF Group Replication')
 
     @mock.patch.object(rest.PowerMaxRest, 'srdf_modify_group')
@@ -2102,12 +2104,14 @@ class PowerMaxRestTest(test.TestCase):
         rdf_group_no = self.data.rdf_group_no_1
         sg_name = self.data.default_sg_re_enabled
         rep_extra_specs = self.data.rep_extra_specs
-
         self.rest.srdf_suspend_replication(
             array_id, sg_name, rdf_group_no, rep_extra_specs)
+        # Replication mode in this test is synchronous, so the expecation
+        # is that the consistency exempt flag is false.
         mck_modify.assert_called_once_with(
             array_id, rdf_group_no, sg_name,
-            {'suspend': {'force': 'true'}, 'action': 'Suspend'},
+            {'suspend': {'force': 'true', 'consExempt': 'false'},
+             'action': 'Suspend'},
             rep_extra_specs, 'Suspend SRDF Group Replication')
 
     @mock.patch.object(rest.PowerMaxRest, 'srdf_modify_group')

cinder/volume/drivers/dell_emc/powermax/rest.py

@@ -2906,21 +2906,6 @@ class PowerMaxRest(object):
                 number = None
         return number
 
-    def _get_async_payload_info(self, array, rdf_group_no):
-        """Get the payload details for an async create pair.
-
-        :param array: the array serial number
-        :param rdf_group_no: the rdf group number
-        :returns: payload_update
-        """
-        num_vols, payload_update = 0, {}
-        rdfg_details = self.get_rdf_group(array, rdf_group_no)
-        if rdfg_details is not None and rdfg_details.get('numDevices'):
-            num_vols = int(rdfg_details['numDevices'])
-        if num_vols > 0:
-            payload_update = {'exempt': 'true'}
-        return payload_update
-
     def get_metro_payload_info(self, array, payload,
                                rdf_group_no, extra_specs, next_gen):
         """Get the payload details for a metro active create pair.
@@ -3026,15 +3011,48 @@ class PowerMaxRest(object):
 
         if group_state:
             group_state = [x.lower() for x in group_state]
-
         if len(group_state) == 1 and utils.RDF_SUSPENDED_STATE in group_state:
             LOG.info('SRDF Group %(grp_num)s is already in a suspended state',
                      {'grp_num': rdf_group_no})
         else:
+            cons_exempt = self._get_cons_exempt(
+                array_id, storage_group, rdf_group_no,
+                rep_extra_specs['rep_mode'])
+            payload = {"suspend": {"force": "true"}, "action": "Suspend"}
+            payload["suspend"]["consExempt"] = (
+                "true" if cons_exempt else "false")
             self.srdf_modify_group(
                 array_id, rdf_group_no, storage_group,
-                {"suspend": {"force": "true"}, "action": "Suspend"},
-                rep_extra_specs, 'Suspend SRDF Group Replication')
+                payload, rep_extra_specs,
+                'Suspend SRDF Group Replication')
+
+    def _get_cons_exempt(self, array_id, storage_group, rdf_group_no,
+                         rep_mode=None):
+        """Get the consistency exempt flag for a storage group.
+
+        :param array_id: array serial number
+        :param storage_group: storage group name
+        :param rdf_group_no: RDF group number
+        :param rep_mode: Replication mode of the SRDF session
+        :returns: A boolean indicating if consistency is exempt
+        """
+        if not rep_mode:
+            return False
+
+        resource = ('storagegroup/%(sg)s/rdf_group/%(rdfg)s' % {
+            'sg': storage_group, 'rdfg': rdf_group_no})
+        rdf_group = self.get_resource(array_id, REPLICATION, resource)
+        modes = list(rep_mode)
+
+        if rdf_group and rdf_group.get('modes'):
+            modes.append(rdf_group.get('modes'))
+        # Ensure we don't see the error message:
+        # "A problem occurred modifying the Storage Group
+        # SRDF Group resource: The device is not in
+        # asynchronous mode"
+        cons_exempt = utils.REP_ASYNC in modes
+        LOG.debug("Consistency exempt: %s", cons_exempt)
+        return cons_exempt
 
     def srdf_resume_replication(self, array_id, storage_group, rdf_group_no,
                                 rep_extra_specs, async_call=True):

releasenotes/notes/bp-dell-powermax-consistency-exempt.yaml

@@ -0,0 +1,17 @@
+---
+features:
+  - |
+    Dell PowerMax Driver: use consistency exempt flag consistently
+    PowerMax allows volumes to be added, removed, or suspended without
+    affecting the state of the SRDF/A or SRDF/Metro session or requiring
+    that other volumes in the session be suspended. Known as --exempt for
+    symcli and editStorageGroupActionParam in the PowerMax REST API,
+    this capability is available for an SRDF group supporting an active
+    SRDF/A session or an active SRDF/Metro session.
+
+    The PowerMax Cinder driver currently uses the exempt flag when
+    volumes are added to SRDF groups, but not when volumes are
+    removed. This incurs an unnecessary performance penalty that is
+    resolved by this change.
+
+    Blueprint: dell-powermax-srdf-exempt