From ad04015c9f17d35b441764c16eaee8f665ecb352 Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Tue, 25 Oct 2016 18:53:31 -0400
Subject: [PATCH] Multi-ancestor detector added.

---
 awx/api/views.py                 |  6 ++++--
 awx/main/scheduler/dag_simple.py | 13 +++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/awx/api/views.py b/awx/api/views.py
index 90621155c5..a5a85f2fdf 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -71,7 +71,6 @@ from awx.api.metadata import RoleMetadata
 from awx.main.consumers import emit_channel_notification
 from awx.main.scheduler.dag_simple import SimpleDAG
 
-
 logger = logging.getLogger('awx.api.views')
 
 def api_exception_handler(exc, context):
@@ -2677,7 +2676,10 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
             graph.add_edge(parent, sub, self.relationship)
 
         if graph.cycle_detected():
-            return {"Error": "cycle detected!"}
+            return {"Error": "Cycle detected!"}
+
+        if graph.multi_ancestor_detected():
+            return {"Error": "Multiple ancestor detected!"}
 
         return None
 
diff --git a/awx/main/scheduler/dag_simple.py b/awx/main/scheduler/dag_simple.py
index f28ad83184..e629eccd98 100644
--- a/awx/main/scheduler/dag_simple.py
+++ b/awx/main/scheduler/dag_simple.py
@@ -174,3 +174,16 @@ class SimpleDAG(object):
 
         self._clean_meta()
         return False
+
+    def multi_ancestor_detected(self):
+        for node in self.nodes:
+            node['metadata'] = {"ancestor": None}
+        for edge in self.edges:
+            if self.nodes[edge[1]]['metadata']['ancestor'] is None:
+                self.nodes[edge[1]]['metadata']['ancestor'] = self.nodes[edge[0]]
+            else:
+                self._clean_meta()
+                return True
+
+        self._clean_meta()
+        return False