Remove backend spec from share type while creating replica

If a share type includes the share_backend_name spec,
the scheduler may fail to schedule share replicas unless
all backends in a replication domain share the same
value for the capability "share_backend_name". Having
the same "share_backend_name" isn't desirable all the
time.

Ignore the share_backend_name spec from share type
while creating replica, so the scheduler will filter
a available backend according to the selection policy.

Change-Id: Ic8f7e6230298c222cc6cb5e4e4e8189524aaa81f
Closes-Bug: #1634734

manila/scheduler/drivers/filter.py

@@ -174,6 +174,11 @@ class FilterScheduler(base.Scheduler):
             if ar_host:
                 replication_domain = ar_host.replication_domain
 
+            # NOTE(zengyingzhe): remove the 'share_backend_name' extra spec,
+            # let scheduler choose the available host for this replica
+            # creation request.
+            share_type.get('extra_specs', {}).pop('share_backend_name', None)
+
         if filter_properties is None:
             filter_properties = {}
         self._populate_retry_share(filter_properties, resource_properties)

manila/tests/scheduler/drivers/test_filter.py

@@ -60,6 +60,35 @@ class FilterSchedulerTestCase(test_base.SchedulerTestCase):
 
         self.assertIn('replication_domain', retval[0])
 
+    @ddt.data(True, False)
+    def test__format_filter_properties_backend_specified_for_replica(
+            self, has_share_backend_name):
+        sched = fakes.FakeFilterScheduler()
+        fake_context = context.RequestContext('user', 'project')
+        request_spec = {
+            'share_properties': {'project_id': 1, 'size': 1},
+            'share_instance_properties': {},
+            'share_type': {
+                'name': 'NFS',
+                'extra_specs': {},
+            },
+            'share_id': 'fake-id1',
+            'active_replica_host': 'fake_ar_host',
+        }
+
+        if has_share_backend_name:
+            request_spec['share_type']['extra_specs'].update(
+                {'share_backend_name': 'fake_backend'})
+
+        self.mock_object(sched.host_manager, 'get_all_host_states_share',
+                         mock.Mock(return_value=[]))
+
+        retval = sched._format_filter_properties(
+            fake_context, {}, request_spec)
+
+        self.assertNotIn('share_backend_name',
+                         retval[0]['share_type']['extra_specs'])
+
     def test_create_share_no_hosts(self):
         # Ensure empty hosts/child_zones result in NoValidHosts exception.
         sched = fakes.FakeFilterScheduler()

releasenotes/notes/bug-1634734-fix-backend-extraspec-for-replication-d611d2227997ae3e.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Share type extra-specification ``share_backend_name`` is now ignored when
+    creating share replicas. This ensures that backends in the same
+    replication domain need not have the same value of ``share_backend_name``.
+    See `launchpad bug #1634734 <https://bugs.launchpad.net/manila/+bug/1634734>`_
+    for details.