Save snapshot to db before stack snapshot complete

When executing stack snapshot heat do not release stack lock
some undefined amount of time because it needs to prepare
some data for stack snapshot. It leads to situation when stack
snapshot is complete(from user perspective) but nobody can do any
operations with stack. So the fix executes snapshot saving to DB
right before stack becomes complete.

Change-Id: Id011142498fee49fee9ec1437fc0816b25780e48
Closes-bug: #1456672

heat/engine/service.py

@@ -1277,13 +1277,18 @@ class EngineService(service.Service):
     @context.request_context
     def stack_snapshot(self, cnxt, stack_identity, name):
         def _stack_snapshot(stack, snapshot):
-            LOG.debug("snapshotting stack %s" % stack.name)
-            stack.snapshot()
-            data = stack.prepare_abandon()
-            snapshot_object.Snapshot.update(
-                cnxt, snapshot.id,
-                {'data': data, 'status': stack.status,
-                 'status_reason': stack.status_reason})
+
+            def save_snapshot(stack, action, status, reason):
+                """Function that saves snapshot before snapshot complete."""
+                data = stack.prepare_abandon()
+                data["status"] = status
+                snapshot_object.Snapshot.update(
+                    cnxt, snapshot.id,
+                    {'data': data, 'status': status,
+                     'status_reason': reason})
+
+            LOG.debug("Snapshotting stack %s" % stack.name)
+            stack.snapshot(save_snapshot_func=save_snapshot)
 
         s = self._get_stack(cnxt, stack_identity)
 

heat/engine/stack.py

@@ -777,10 +777,22 @@ class Stack(collections.Mapping):
     @scheduler.wrappertask
     def stack_task(self, action, reverse=False, post_func=None,
                    error_wait_time=None,
-                   aggregate_exceptions=False):
+                   aggregate_exceptions=False, pre_completion_func=None):
         '''
         A task to perform an action on the stack and all of the resources
         in forward or reverse dependency order as specified by reverse
+
+        :param action action that should be executed with stack resources
+        :param reverse defines if action on the resources need to be executed
+         in reverse order (resources - first and then res dependencies )
+        :param post_func function that need to be executed after
+        action complete on the stack
+        :param error_wait_time time to wait before cancelling all execution
+        threads when an error occurred
+        :param aggregate_exceptions defines if exceptions should be aggregated
+        :param pre_completion_func function that need to be executed right
+        before action completion. Uses stack ,action, status and reason as
+        input parameters
         '''
         try:
             lifecycle_plugin_utils.do_pre_ops(self.context, self,
@@ -829,6 +841,9 @@ class Stack(collections.Mapping):
             stack_status = self.FAILED
             reason = 'Resource %s failed: %s' % (action, six.text_type(ex))
 
+        if pre_completion_func:
+            pre_completion_func(self, action, stack_status, reason)
+
         self.state_set(action, stack_status, reason)
 
         if callable(post_func):
@@ -1431,12 +1446,12 @@ class Stack(collections.Mapping):
         sus_task(timeout=self.timeout_secs())
 
     @profiler.trace('Stack.snapshot', hide_args=False)
-    def snapshot(self):
+    def snapshot(self, save_snapshot_func):
         '''Snapshot the stack, invoking handle_snapshot on all resources.'''
         self.updated_time = datetime.datetime.utcnow()
-        sus_task = scheduler.TaskRunner(self.stack_task,
-                                        action=self.SNAPSHOT,
-                                        reverse=False)
+        sus_task = scheduler.TaskRunner(self.stack_task, action=self.SNAPSHOT,
+                                        reverse=False,
+                                        pre_completion_func=save_snapshot_func)
         sus_task(timeout=self.timeout_secs())
 
     @profiler.trace('Stack.delete_snapshot', hide_args=False)

heat/tests/openstack/test_volume.py

@@ -1034,7 +1034,7 @@ class CinderVolumeTest(vt_base.BaseVolumeTest):
 
         self.assertEqual((stack.CREATE, stack.COMPLETE), stack.state)
 
-        scheduler.TaskRunner(stack.snapshot)()
+        scheduler.TaskRunner(stack.snapshot, None)()
 
         self.assertEqual((stack.SNAPSHOT, stack.COMPLETE), stack.state)
 

heat/tests/test_server.py

@@ -3280,7 +3280,7 @@ class ServersTest(common.HeatTestCase):
 
         self.assertEqual((stack.CREATE, stack.COMPLETE), stack.state)
 
-        scheduler.TaskRunner(stack.snapshot)()
+        scheduler.TaskRunner(stack.snapshot, None)()
 
         self.assertEqual((stack.SNAPSHOT, stack.COMPLETE), stack.state)
 

heat/tests/test_stack.py

@@ -1796,6 +1796,21 @@ class StackTest(common.HeatTestCase):
                          '(AResource Bar) is incorrect.',
                          six.text_type(ex))
 
+    def test_snapshot_save_called_first(self):
+        def snapshotting_called_first(stack, action, status, reason):
+            self.assertEqual(stack.status, stack.IN_PROGRESS)
+            self.assertEqual(stack.action, stack.SNAPSHOT)
+
+        tmpl = {'HeatTemplateFormatVersion': '2012-12-12',
+                'Resources': {
+                    'A': {'Type': 'GenericResourceType'},
+                    'B': {'Type': 'GenericResourceType'}}}
+        self.stack = stack.Stack(self.ctx, 'stack_details_test',
+                                 template.Template(tmpl))
+        self.stack.store()
+        self.stack.create()
+        self.stack.snapshot(save_snapshot_func=snapshotting_called_first)
+
     def test_restore(self):
         tmpl = {'HeatTemplateFormatVersion': '2012-12-12',
                 'Resources': {