From 6f361f7da39c9567456d05523358aa6b65221798 Mon Sep 17 00:00:00 2001
From: Anant Patil <anant.patil@hp.com>
Date: Thu, 5 May 2016 18:35:38 +0530
Subject: [PATCH] Fix DBDeadlock error in stack update

Fix the DBDeadlock error encounter occasionally when stack is being
updated in DB.

Change-Id: I24a929d88d87c5c6d6b410ad990d8d027f4c5b1b
Closes-Bug: #1578615
---
 heat/db/sqlalchemy/api.py            | 2 ++
 heat/tests/db/test_sqlalchemy_api.py | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/heat/db/sqlalchemy/api.py b/heat/db/sqlalchemy/api.py
index 773beac52c..1f537ee9bb 100644
--- a/heat/db/sqlalchemy/api.py
+++ b/heat/db/sqlalchemy/api.py
@@ -529,6 +529,8 @@ def stack_create(context, values):
     return stack_ref
 
 
+@oslo_db_api.wrap_db_retry(max_retries=3, retry_on_deadlock=True,
+                           retry_interval=0.5, inc_retry_interval=True)
 def stack_update(context, stack_id, values, exp_trvsl=None):
     stack = stack_get(context, stack_id)
 
diff --git a/heat/tests/db/test_sqlalchemy_api.py b/heat/tests/db/test_sqlalchemy_api.py
index 6ca151fcfc..4e03108932 100644
--- a/heat/tests/db/test_sqlalchemy_api.py
+++ b/heat/tests/db/test_sqlalchemy_api.py
@@ -1750,6 +1750,15 @@ class DBAPIStackTest(common.HeatTestCase):
                                       exp_trvsl=diff_uuid)
         self.assertFalse(updated)
 
+    @mock.patch.object(time, 'sleep')
+    def test_stack_update_retries_on_deadlock(self, sleep):
+        stack = create_stack(self.ctx, self.template, self.user_creds)
+        with mock.patch('sqlalchemy.orm.query.Query.update',
+                        side_effect=db_exception.DBDeadlock) as mock_update:
+            self.assertRaises(db_exception.DBDeadlock,
+                              db_api.stack_update, self.ctx, stack.id, {})
+            self.assertEqual(4, mock_update.call_count)
+
     def test_stack_set_status_release_lock(self):
         stack = create_stack(self.ctx, self.template, self.user_creds)
         values = {