Allow scale-down of ASG as part of update

When user wants to do manual scale-up of ASG by increasing the
desired_capacity and also update some member properties as
part of a stack update, if it fails due to insufficient
resources when resizing, trying to manually scale-down by
decreasing the desired_capacity won't work, as it would
always expect to update the group with the earlier size
before scaling down.

This patch uses the target_size when building the batches.

Task: 39867
Change-Id: Id851530b424f68b5e0e967fe34431483bfffd852
(cherry picked from commit 26d8f64fc90ed9b3ad0413ed0c932fb91b51d666)

4 files changed, 55 insertions, 39 deletions

diff --git a/heat/engine/resources/aws/autoscaling/autoscaling_group.py b/heat/engine/resources/aws/autoscaling/autoscaling_group.py
index 481cca7cd..189e9fc1f 100644
--- a/heat/engine/resources/aws/autoscaling/autoscaling_group.py
+++ b/heat/engine/resources/aws/autoscaling/autoscaling_group.py
@@ -186,6 +186,10 @@ class AutoScalingGroup(cooldown.CooldownMixin, instgrp.InstanceGroup):
                                           schema=rolling_update_schema)
     }
 
+    def get_size(self):
+        """Get desired capacity."""
+        return self.properties[self.DESIRED_CAPACITY]
+
     def handle_create(self):
         return self.create_with_template(self.child_template())
 
diff --git a/heat/engine/resources/openstack/heat/instance_group.py b/heat/engine/resources/openstack/heat/instance_group.py
index 103737d44..3f0678cf6 100644
--- a/heat/engine/resources/openstack/heat/instance_group.py
+++ b/heat/engine/resources/openstack/heat/instance_group.py
@@ -140,6 +140,10 @@ class InstanceGroup(stack_resource.StackResource):
                                           schema=rolling_update_schema)
     }
 
+    def get_size(self):
+        """Get desired size."""
+        return self.properties[self.SIZE]
+
     def validate(self):
         """Add validation for update_policy."""
         self.validate_launchconfig()
@@ -335,7 +339,12 @@ class InstanceGroup(stack_resource.StackResource):
         old_template = group_data.template()
 
         capacity = group_data.size(include_failed=True)
-        batches = list(self._get_batches(capacity, batch_size, min_in_service))
+
+        target_capacity = min(self.get_size() or capacity, capacity)
+
+        batches = list(self._get_batches(target_capacity,
+                                         capacity, batch_size,
+                                         min_in_service))
 
         update_timeout = self._update_timeout(len(batches), pause_sec)
 
@@ -359,7 +368,7 @@ class InstanceGroup(stack_resource.StackResource):
             self._lb_reload()
 
     @staticmethod
-    def _get_batches(capacity, batch_size, min_in_service):
+    def _get_batches(target_capacity, capacity, batch_size, min_in_service):
         """Return an iterator over the batches in a batched update.
 
         Each batch is a tuple comprising the total size of the group after
@@ -368,15 +377,14 @@ class InstanceGroup(stack_resource.StackResource):
         updating an existing one).
         """
 
-        efft_capacity = capacity
         updated = 0
 
-        while rolling_update.needs_update(capacity, efft_capacity, updated):
-            batch = rolling_update.next_batch(capacity, efft_capacity,
+        while rolling_update.needs_update(target_capacity, capacity, updated):
+            batch = rolling_update.next_batch(target_capacity, capacity,
                                               updated, batch_size,
                                               min_in_service)
             yield batch
-            efft_capacity, num_updates = batch
+            capacity, num_updates = batch
             updated += num_updates
 
     def _check_for_completion(self, updater):
diff --git a/heat/tests/openstack/heat/test_instance_group.py b/heat/tests/openstack/heat/test_instance_group.py
index c13214c8e..cfc0de7b1 100644
--- a/heat/tests/openstack/heat/test_instance_group.py
+++ b/heat/tests/openstack/heat/test_instance_group.py
@@ -482,42 +482,45 @@ class ResizeWithFailedInstancesTest(InstanceGroupWithNestedStack):
 class TestGetBatches(common.HeatTestCase):
 
     scenarios = [
-        ('4_1_0', dict(curr_cap=4, bat_size=1, min_serv=0,
-                       batches=[(4, 1)] * 4)),
-        ('4_1_4', dict(curr_cap=4, bat_size=1, min_serv=4,
-                       batches=([(5, 1)] * 4) + [(4, 0)])),
-        ('4_1_5', dict(curr_cap=4, bat_size=1, min_serv=5,
-                       batches=([(5, 1)] * 4) + [(4, 0)])),
-        ('4_2_0', dict(curr_cap=4, bat_size=2, min_serv=0,
-                       batches=[(4, 2)] * 2)),
-        ('4_2_4', dict(curr_cap=4, bat_size=2, min_serv=4,
-                       batches=([(6, 2)] * 2) + [(4, 0)])),
-        ('5_2_0', dict(curr_cap=5, bat_size=2, min_serv=0,
-                       batches=([(5, 2)] * 2) + [(5, 1)])),
-        ('5_2_4', dict(curr_cap=5, bat_size=2, min_serv=4,
-                       batches=([(6, 2)] * 2) + [(5, 1)])),
-        ('3_2_0', dict(curr_cap=3, bat_size=2, min_serv=0,
-                       batches=[(3, 2), (3, 1)])),
-        ('3_2_4', dict(curr_cap=3, bat_size=2, min_serv=4,
-                       batches=[(5, 2), (4, 1), (3, 0)])),
-        ('4_4_0', dict(curr_cap=4, bat_size=4, min_serv=0,
-                       batches=[(4, 4)])),
-        ('4_5_0', dict(curr_cap=4, bat_size=5, min_serv=0,
-                       batches=[(4, 4)])),
-        ('4_4_1', dict(curr_cap=4, bat_size=4, min_serv=1,
-                       batches=[(5, 4), (4, 0)])),
-        ('4_6_1', dict(curr_cap=4, bat_size=6, min_serv=1,
-                       batches=[(5, 4), (4, 0)])),
-        ('4_4_2', dict(curr_cap=4, bat_size=4, min_serv=2,
-                       batches=[(6, 4), (4, 0)])),
-        ('4_4_4', dict(curr_cap=4, bat_size=4, min_serv=4,
-                       batches=[(8, 4), (4, 0)])),
-        ('4_5_6', dict(curr_cap=4, bat_size=5, min_serv=6,
-                       batches=[(8, 4), (4, 0)])),
+        ('4_4_1_0', dict(tgt_cap=4, curr_cap=4, bat_size=1, min_serv=0,
+                         batches=[(4, 1)] * 4)),
+        ('3_4_1_0', dict(tgt_cap=3, curr_cap=4, bat_size=1, min_serv=0,
+                         batches=[(3, 1)] * 3)),
+        ('4_4_1_4', dict(tgt_cap=4, curr_cap=4, bat_size=1, min_serv=4,
+                         batches=([(5, 1)] * 4) + [(4, 0)])),
+        ('4_4_1_5', dict(tgt_cap=4, curr_cap=4, bat_size=1, min_serv=5,
+                         batches=([(5, 1)] * 4) + [(4, 0)])),
+        ('4_4_2_0', dict(tgt_cap=4, curr_cap=4, bat_size=2, min_serv=0,
+                         batches=[(4, 2)] * 2)),
+        ('4_4_2_4', dict(tgt_cap=4, curr_cap=4, bat_size=2, min_serv=4,
+                         batches=([(6, 2)] * 2) + [(4, 0)])),
+        ('5_5_2_0', dict(tgt_cap=5, curr_cap=5, bat_size=2, min_serv=0,
+                         batches=([(5, 2)] * 2) + [(5, 1)])),
+        ('5_5_2_4', dict(tgt_cap=5, curr_cap=5, bat_size=2, min_serv=4,
+                         batches=([(6, 2)] * 2) + [(5, 1)])),
+        ('3_3_2_0', dict(tgt_cap=3, curr_cap=3, bat_size=2, min_serv=0,
+                         batches=[(3, 2), (3, 1)])),
+        ('3_3_2_4', dict(tgt_cap=3, curr_cap=3, bat_size=2, min_serv=4,
+                         batches=[(5, 2), (4, 1), (3, 0)])),
+        ('4_4_4_0', dict(tgt_cap=4, curr_cap=4, bat_size=4, min_serv=0,
+                         batches=[(4, 4)])),
+        ('4_4_5_0', dict(tgt_cap=4, curr_cap=4, bat_size=5, min_serv=0,
+                         batches=[(4, 4)])),
+        ('4_4_4_1', dict(tgt_cap=4, curr_cap=4, bat_size=4, min_serv=1,
+                         batches=[(5, 4), (4, 0)])),
+        ('4_4_6_1', dict(tgt_cap=4, curr_cap=4, bat_size=6, min_serv=1,
+                         batches=[(5, 4), (4, 0)])),
+        ('4_4_4_2', dict(tgt_cap=4, curr_cap=4, bat_size=4, min_serv=2,
+                         batches=[(6, 4), (4, 0)])),
+        ('4_4_4_4', dict(tgt_cap=4, curr_cap=4, bat_size=4, min_serv=4,
+                         batches=[(8, 4), (4, 0)])),
+        ('4_4_5_6', dict(tgt_cap=4, curr_cap=4, bat_size=5, min_serv=6,
+                         batches=[(8, 4), (4, 0)])),
     ]
 
     def test_get_batches(self):
-        batches = list(instgrp.InstanceGroup._get_batches(self.curr_cap,
+        batches = list(instgrp.InstanceGroup._get_batches(self.tgt_cap,
+                                                          self.curr_cap,
                                                           self.bat_size,
                                                           self.min_serv))
         self.assertEqual(self.batches, batches)
diff --git a/heat/tests/openstack/heat/test_instance_group_update_policy.py b/heat/tests/openstack/heat/test_instance_group_update_policy.py
index 9ece3aa28..02bb79258 100644
--- a/heat/tests/openstack/heat/test_instance_group_update_policy.py
+++ b/heat/tests/openstack/heat/test_instance_group_update_policy.py
@@ -298,5 +298,6 @@ class InstanceGroupReplaceTest(common.HeatTestCase):
 
         group = instgrp.InstanceGroup('asg', defn, stack)
         group._group_data().size = mock.Mock(return_value=12)
+        group.get_size = mock.Mock(return_value=12)
         self.assertRaises(ValueError,
                           group._replace, 10, 1, 14 * 60)