Add methods to get an existing stack

* Add yardstick/orchestrator/heat.py:HeatStack.get
* Add yardstick/benchmark/contexts/heay.py:HeatContext.retrieve_existing_stack

JIRA: YARDSTICK-886
Change-Id: I6974b79a25f98066a49b1bc8ccd11383e7962091
Signed-off-by: Emma Foley <emma.l.foley@intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/yardstick/benchmark/contexts/heat.py b/yardstick/benchmark/contexts/heat.py
index be8815060..ed301a998 100644
--- a/yardstick/benchmark/contexts/heat.py
+++ b/yardstick/benchmark/contexts/heat.py
@@ -26,6 +26,7 @@ from yardstick.benchmark.contexts.model import Server
 from yardstick.benchmark.contexts.model import update_scheduler_hints
 from yardstick.common import exceptions as y_exc
 from yardstick.common.openstack_utils import get_neutron_client
+from yardstick.orchestrator.heat import HeatStack
 from yardstick.orchestrator.heat import HeatTemplate
 from yardstick.common import constants as consts
 from yardstick.common.utils import source_env
@@ -312,6 +313,14 @@ class HeatContext(Context):
              # let the other failures happen, we want stack trace
              raise
 
+    def _retrieve_existing_stack(self, stack_name):
+        stack = HeatStack(stack_name)
+        if stack.get():
+            return stack
+        else:
+            LOG.warning("Stack %s does not exist", self.name)
+            return None
+
     def deploy(self):
         """deploys template into a stack using cloud"""
         LOG.info("Deploying context '%s' START", self.name)