From 88025d0733f765cad08cef1e643143cfd0f144b9 Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Mon, 24 Oct 2016 17:32:30 -0400
Subject: [PATCH 01/10] Basic verification architecture added.

---
 awx/api/generics.py              |  8 ++++++++
 awx/api/views.py                 | 25 +++++++++++++++++++++++++
 awx/main/scheduler/dag_simple.py |  3 +++
 3 files changed, 36 insertions(+)

diff --git a/awx/api/generics.py b/awx/api/generics.py
index 4c4247b23d..7b58f14edb 100644
--- a/awx/api/generics.py
+++ b/awx/api/generics.py
@@ -370,6 +370,9 @@ class SubListCreateAttachDetachAPIView(SubListCreateAPIView):
     # Base class for a sublist view that allows for creating subobjects and
     # attaching/detaching them from the parent.
 
+    def is_valid_relation(self, parent, sub):
+        return None
+
     def get_description_context(self):
         d = super(SubListCreateAttachDetachAPIView, self).get_description_context()
         d.update({
@@ -406,6 +409,11 @@ class SubListCreateAttachDetachAPIView(SubListCreateAPIView):
                                        skip_sub_obj_read_check=created):
             raise PermissionDenied()
 
+        # Verify that the relationship to be added is valid.
+        attach_errors = self.is_valid_relation(parent, sub)
+        if attach_errors is not None:
+            return Response(attach_errors, status=status.HTTP_400_BAD_REQUEST)
+
         # Attach the object to the collection.
         if sub not in relationship.all():
             relationship.add(sub)
diff --git a/awx/api/views.py b/awx/api/views.py
index 699d5c9e81..90621155c5 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -69,6 +69,8 @@ from awx.api.renderers import * # noqa
 from awx.api.serializers import * # noqa
 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')
 
@@ -2656,6 +2658,29 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
         self.check_parent_access(parent)
         return getattr(parent, self.relationship).all()
 
+    def is_valid_relation(self, parent, sub):
+        workflow_nodes = parent.workflow_job_template.workflow_job_template_nodes.all()
+        graph = SimpleDAG()
+        for workflow_node in workflow_nodes:
+            graph.add_node(workflow_node)
+
+        find = False
+        for node_type in ['success_nodes', 'failure_nodes', 'always_nodes']:
+            for workflow_node in workflow_nodes:
+                related_nodes = getattr(workflow_node, node_type).all()
+                for related_node in related_nodes:
+                    graph.add_edge(workflow_node, related_node, node_type)
+                    if not find and parent == workflow_node and\
+                       sub == related_node and self.relationship == node_type:
+                        find = True
+        if not find:
+            graph.add_edge(parent, sub, self.relationship)
+
+        if graph.cycle_detected():
+            return {"Error": "cycle detected!"}
+
+        return None
+
 class WorkflowJobTemplateNodeSuccessNodesList(WorkflowJobTemplateNodeChildrenBaseList):
     relationship = 'success_nodes'
 
diff --git a/awx/main/scheduler/dag_simple.py b/awx/main/scheduler/dag_simple.py
index aeb0ff759e..3fbb16901f 100644
--- a/awx/main/scheduler/dag_simple.py
+++ b/awx/main/scheduler/dag_simple.py
@@ -138,3 +138,6 @@ class SimpleDAG(object):
                 roots.append(n)
         return roots
 
+    # TODO
+    def cycle_detected(self):
+        return False

From 279255551060d281f6133dcf63a2eb7d97533e98 Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Tue, 25 Oct 2016 17:02:37 -0400
Subject: [PATCH 02/10] Cycle detector added.

---
 awx/main/scheduler/dag_simple.py | 37 ++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/awx/main/scheduler/dag_simple.py b/awx/main/scheduler/dag_simple.py
index 3fbb16901f..f28ad83184 100644
--- a/awx/main/scheduler/dag_simple.py
+++ b/awx/main/scheduler/dag_simple.py
@@ -138,6 +138,39 @@ class SimpleDAG(object):
                 roots.append(n)
         return roots
 
-    # TODO
-    def cycle_detected(self):
+    def _find_cycle(self, node):
+        stack = [node]
+        node['metadata']['color'] = 'gray'
+
+        while len(stack) > 0:
+            if stack[-1]['metadata']['count'] == len(stack[-1]['metadata']['adj_list']):
+                stack[-1]['metadata']['color'] = 'black'
+                stack.pop()
+            else:
+                to_push = stack[-1]['metadata']['adj_list'][stack[-1]['metadata']['count']]
+                stack[-1]['metadata']['count'] += 1
+                if to_push['metadata']['color'] == 'gray':
+                    return True
+                elif to_push['metadata']['color'] == 'white':
+                    to_push['metadata']['color'] = 'gray'
+                    stack.append(to_push)
+
+        return False
+
+    def _clean_meta(self):
+        for node in self.nodes:
+            node['metadata'] = None
+
+    def cycle_detected(self):
+        for node in self.nodes:
+            node['metadata'] = {"adj_list": [], "color": "white", "count": 0}
+        for edge in self.edges:
+            self.nodes[edge[0]]['metadata']['adj_list'].append(self.nodes[edge[1]])
+
+        for node in self.nodes:
+            if node['metadata']['color'] == 'white' and self._find_cycle(node):
+                self._clean_meta()
+                return True
+
+        self._clean_meta()
         return False

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 03/10] 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

From 02cccf35d3363a3bb29e576bd155f199d3e9c2ef Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Thu, 27 Oct 2016 16:27:42 -0400
Subject: [PATCH 04/10] Delete created resource when it fails the relationship
 verification.

---
 awx/api/generics.py | 2 ++
 awx/api/views.py    | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/awx/api/generics.py b/awx/api/generics.py
index 7b58f14edb..7a818722bc 100644
--- a/awx/api/generics.py
+++ b/awx/api/generics.py
@@ -412,6 +412,8 @@ class SubListCreateAttachDetachAPIView(SubListCreateAPIView):
         # Verify that the relationship to be added is valid.
         attach_errors = self.is_valid_relation(parent, sub)
         if attach_errors is not None:
+            if created:
+                sub.delete()
             return Response(attach_errors, status=status.HTTP_400_BAD_REQUEST)
 
         # Attach the object to the collection.
diff --git a/awx/api/views.py b/awx/api/views.py
index a5a85f2fdf..910eae869b 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -2669,8 +2669,10 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
                 related_nodes = getattr(workflow_node, node_type).all()
                 for related_node in related_nodes:
                     graph.add_edge(workflow_node, related_node, node_type)
-                    if not find and parent == workflow_node and\
-                       sub == related_node and self.relationship == node_type:
+                    if (not find and
+                        parent == workflow_node and
+                        sub == related_node and
+                        self.relationship == node_type):
                         find = True
         if not find:
             graph.add_edge(parent, sub, self.relationship)

From 7472cf0dc92a71657a7b0d3f4a0594575e117950 Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Fri, 28 Oct 2016 14:05:44 -0400
Subject: [PATCH 05/10] Refactor for better performance.

---
 awx/api/generics.py              |  4 +--
 awx/api/views.py                 | 40 +++++++++++++------------
 awx/main/scheduler/dag_simple.py | 50 --------------------------------
 3 files changed, 24 insertions(+), 70 deletions(-)

diff --git a/awx/api/generics.py b/awx/api/generics.py
index 7a818722bc..e474a1bafc 100644
--- a/awx/api/generics.py
+++ b/awx/api/generics.py
@@ -370,7 +370,7 @@ class SubListCreateAttachDetachAPIView(SubListCreateAPIView):
     # Base class for a sublist view that allows for creating subobjects and
     # attaching/detaching them from the parent.
 
-    def is_valid_relation(self, parent, sub):
+    def is_valid_relation(self, parent, sub, created=False):
         return None
 
     def get_description_context(self):
@@ -410,7 +410,7 @@ class SubListCreateAttachDetachAPIView(SubListCreateAPIView):
             raise PermissionDenied()
 
         # Verify that the relationship to be added is valid.
-        attach_errors = self.is_valid_relation(parent, sub)
+        attach_errors = self.is_valid_relation(parent, sub, created=created)
         if attach_errors is not None:
             if created:
                 sub.delete()
diff --git a/awx/api/views.py b/awx/api/views.py
index 910eae869b..84306332b0 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -69,7 +69,6 @@ from awx.api.renderers import * # noqa
 from awx.api.serializers import * # noqa
 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')
 
@@ -2657,31 +2656,36 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
         self.check_parent_access(parent)
         return getattr(parent, self.relationship).all()
 
-    def is_valid_relation(self, parent, sub):
-        workflow_nodes = parent.workflow_job_template.workflow_job_template_nodes.all()
-        graph = SimpleDAG()
+    def is_valid_relation(self, parent, sub, created=False):
+        if created:
+            return None
+
+        workflow_nodes = parent.workflow_job_template.workflow_job_template_nodes.all().\
+            prefetch_related('success_nodes', 'failure_nodes', 'always_nodes')
+        graph = {}
         for workflow_node in workflow_nodes:
-            graph.add_node(workflow_node)
+            graph[workflow_node.pk] = dict(node_object=workflow_node, metadata={'parent': None})
 
         find = False
         for node_type in ['success_nodes', 'failure_nodes', 'always_nodes']:
             for workflow_node in workflow_nodes:
-                related_nodes = getattr(workflow_node, node_type).all()
+                parent_node = graph[workflow_node.pk]
+                related_nodes = getattr(parent_node['node_object'], node_type).all()
                 for related_node in related_nodes:
-                    graph.add_edge(workflow_node, related_node, node_type)
-                    if (not find and
-                        parent == workflow_node and
-                        sub == related_node and
-                        self.relationship == node_type):
+                    sub_node = graph[related_node.pk]
+                    sub_node['metadata']['parent'] = parent_node
+                    if not find and parent == workflow_node and sub == related_node and self.relationship == node_type:
                         find = True
         if not find:
-            graph.add_edge(parent, sub, self.relationship)
-
-        if graph.cycle_detected():
-            return {"Error": "Cycle detected!"}
-
-        if graph.multi_ancestor_detected():
-            return {"Error": "Multiple ancestor detected!"}
+            sub_node = graph[sub.pk]
+            parent_node = graph[parent.pk]
+            if sub_node['metadata']['parent'] is not None:
+                return {"Error": "Multiple ancestor detected!"}
+            iter_node = parent_node
+            while iter_node is not None:
+                if iter_node == sub_node:
+                    return {"Error": "Cycle detected!"}
+                iter_node = iter_node['metadata']['parent']
 
         return None
 
diff --git a/awx/main/scheduler/dag_simple.py b/awx/main/scheduler/dag_simple.py
index e629eccd98..c6aa6247c0 100644
--- a/awx/main/scheduler/dag_simple.py
+++ b/awx/main/scheduler/dag_simple.py
@@ -137,53 +137,3 @@ class SimpleDAG(object):
             if len(self.get_dependents(n['node_object'])) < 1:
                 roots.append(n)
         return roots
-
-    def _find_cycle(self, node):
-        stack = [node]
-        node['metadata']['color'] = 'gray'
-
-        while len(stack) > 0:
-            if stack[-1]['metadata']['count'] == len(stack[-1]['metadata']['adj_list']):
-                stack[-1]['metadata']['color'] = 'black'
-                stack.pop()
-            else:
-                to_push = stack[-1]['metadata']['adj_list'][stack[-1]['metadata']['count']]
-                stack[-1]['metadata']['count'] += 1
-                if to_push['metadata']['color'] == 'gray':
-                    return True
-                elif to_push['metadata']['color'] == 'white':
-                    to_push['metadata']['color'] = 'gray'
-                    stack.append(to_push)
-
-        return False
-
-    def _clean_meta(self):
-        for node in self.nodes:
-            node['metadata'] = None
-
-    def cycle_detected(self):
-        for node in self.nodes:
-            node['metadata'] = {"adj_list": [], "color": "white", "count": 0}
-        for edge in self.edges:
-            self.nodes[edge[0]]['metadata']['adj_list'].append(self.nodes[edge[1]])
-
-        for node in self.nodes:
-            if node['metadata']['color'] == 'white' and self._find_cycle(node):
-                self._clean_meta()
-                return True
-
-        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

From 53eb198abbbbe8c49e2b847e4e5cd05c8b02cd28 Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Sun, 30 Oct 2016 14:58:32 -0400
Subject: [PATCH 06/10] Functional test added.

---
 awx/main/tests/functional/models/test_workflow.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/awx/main/tests/functional/models/test_workflow.py b/awx/main/tests/functional/models/test_workflow.py
index 0c3d5d88be..b8053ff9b2 100644
--- a/awx/main/tests/functional/models/test_workflow.py
+++ b/awx/main/tests/functional/models/test_workflow.py
@@ -90,6 +90,17 @@ class TestWorkflowJobTemplate:
         assert len(parent_qs) == 1
         assert parent_qs[0] == wfjt.workflow_job_template_nodes.all()[1]
 
+    def test_topology_validator(self, wfjt):
+        from awx.api.views import WorkflowJobTemplateNodeChildrenBaseList
+        test_view = WorkflowJobTemplateNodeChildrenBaseList()
+        nodes = wfjt.workflow_job_template_nodes.all()
+        node_assoc = WorkflowJobTemplateNode.objects.create(workflow_job_template=wfjt)
+        nodes[2].always_nodes.add(node_assoc)
+        # test cycle validation
+        assert test_view.is_valid_relation(node_assoc, nodes[0]) == {'Error': 'Cycle detected!'}
+        # test multi-ancestor validation
+        assert test_view.is_valid_relation(node_assoc, nodes[1]) == {'Error': 'Multiple ancestor detected!'}
+
 @pytest.mark.django_db
 class TestWorkflowJobFailure:
     """

From a85075aceab787a10642f6dedf369b48055a919e Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Sun, 30 Oct 2016 15:36:28 -0400
Subject: [PATCH 07/10] Mutex validator added.

---
 awx/api/views.py                                  | 5 +++++
 awx/main/tests/functional/models/test_workflow.py | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/awx/api/views.py b/awx/api/views.py
index 84306332b0..1e5c4284b9 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -2657,6 +2657,11 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
         return getattr(parent, self.relationship).all()
 
     def is_valid_relation(self, parent, sub, created=False):
+        mutex_list = ('success_nodes', 'failure_nodes') if self.relationship == 'always_nodes' else ('always_nodes',)
+        for relation in mutex_list:
+            if getattr(parent, relation).all().exists():
+                return {'Error': 'Cannot associate {0} when {1} have been associated.'.format(self.relationship, relation)}
+
         if created:
             return None
 
diff --git a/awx/main/tests/functional/models/test_workflow.py b/awx/main/tests/functional/models/test_workflow.py
index b8053ff9b2..0d39d6c091 100644
--- a/awx/main/tests/functional/models/test_workflow.py
+++ b/awx/main/tests/functional/models/test_workflow.py
@@ -100,6 +100,11 @@ class TestWorkflowJobTemplate:
         assert test_view.is_valid_relation(node_assoc, nodes[0]) == {'Error': 'Cycle detected!'}
         # test multi-ancestor validation
         assert test_view.is_valid_relation(node_assoc, nodes[1]) == {'Error': 'Multiple ancestor detected!'}
+        # test mutex validation
+        test_view.relationship = 'failure_nodes'
+        node_assoc_1 = WorkflowJobTemplateNode.objects.create(workflow_job_template=wfjt)
+        assert (test_view.is_valid_relation(nodes[2], node_assoc_1) ==
+                {'Error': 'Cannot associate failure_nodes when always_nodes have been associated.'})
 
 @pytest.mark.django_db
 class TestWorkflowJobFailure:

From ff1fdb4f5b6b07ca59fbc519534773bd7d31380b Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Tue, 1 Nov 2016 15:07:36 -0400
Subject: [PATCH 08/10] Error message text improvement.

---
 awx/api/views.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/awx/api/views.py b/awx/api/views.py
index 1e5c4284b9..be4dfe0154 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -2685,11 +2685,11 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
             sub_node = graph[sub.pk]
             parent_node = graph[parent.pk]
             if sub_node['metadata']['parent'] is not None:
-                return {"Error": "Multiple ancestor detected!"}
+                return {"Error": "Multiple parent relationship not allowed."}
             iter_node = parent_node
             while iter_node is not None:
                 if iter_node == sub_node:
-                    return {"Error": "Cycle detected!"}
+                    return {"Error": "Cycle detected."}
                 iter_node = iter_node['metadata']['parent']
 
         return None

From d1ec44f20acfd03bfd574a2fc03ddbf2ae79ebfb Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Tue, 1 Nov 2016 15:35:54 -0400
Subject: [PATCH 09/10] i18n changes.

---
 awx/api/views.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/awx/api/views.py b/awx/api/views.py
index be4dfe0154..b84a226ce2 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -2660,7 +2660,7 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
         mutex_list = ('success_nodes', 'failure_nodes') if self.relationship == 'always_nodes' else ('always_nodes',)
         for relation in mutex_list:
             if getattr(parent, relation).all().exists():
-                return {'Error': 'Cannot associate {0} when {1} have been associated.'.format(self.relationship, relation)}
+                return {'Error': _('Cannot associate {0} when {1} have been associated.'.format(self.relationship, relation))}
 
         if created:
             return None
@@ -2685,11 +2685,11 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
             sub_node = graph[sub.pk]
             parent_node = graph[parent.pk]
             if sub_node['metadata']['parent'] is not None:
-                return {"Error": "Multiple parent relationship not allowed."}
+                return {"Error": _("Multiple parent relationship not allowed.")}
             iter_node = parent_node
             while iter_node is not None:
                 if iter_node == sub_node:
-                    return {"Error": "Cycle detected."}
+                    return {"Error": _("Cycle detected.")}
                 iter_node = iter_node['metadata']['parent']
 
         return None

From 843c48934e952665fcb0483c6ee4dc59a34c7de6 Mon Sep 17 00:00:00 2001
From: Aaron Tan <jangsutsr@gmail.com>
Date: Wed, 2 Nov 2016 11:36:08 -0400
Subject: [PATCH 10/10] Refactor cycle detector to prevent potential inf loop.

---
 awx/api/views.py | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/awx/api/views.py b/awx/api/views.py
index b84a226ce2..4022558385 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -2660,7 +2660,7 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
         mutex_list = ('success_nodes', 'failure_nodes') if self.relationship == 'always_nodes' else ('always_nodes',)
         for relation in mutex_list:
             if getattr(parent, relation).all().exists():
-                return {'Error': _('Cannot associate {0} when {1} have been associated.'.format(self.relationship, relation))}
+                return {'Error': 'Cannot associate {0} when {1} have been associated.'.format(self.relationship, relation)}
 
         if created:
             return None
@@ -2669,7 +2669,7 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
             prefetch_related('success_nodes', 'failure_nodes', 'always_nodes')
         graph = {}
         for workflow_node in workflow_nodes:
-            graph[workflow_node.pk] = dict(node_object=workflow_node, metadata={'parent': None})
+            graph[workflow_node.pk] = dict(node_object=workflow_node, metadata={'parent': None, 'traversed': False})
 
         find = False
         for node_type in ['success_nodes', 'failure_nodes', 'always_nodes']:
@@ -2685,11 +2685,13 @@ class WorkflowJobTemplateNodeChildrenBaseList(EnforceParentRelationshipMixin, Su
             sub_node = graph[sub.pk]
             parent_node = graph[parent.pk]
             if sub_node['metadata']['parent'] is not None:
-                return {"Error": _("Multiple parent relationship not allowed.")}
-            iter_node = parent_node
+                return {"Error": "Multiple parent relationship not allowed."}
+            sub_node['metadata']['parent'] = parent_node
+            iter_node = sub_node
             while iter_node is not None:
-                if iter_node == sub_node:
-                    return {"Error": _("Cycle detected.")}
+                if iter_node['metadata']['traversed']:
+                    return {"Error": "Cycle detected."}
+                iter_node['metadata']['traversed'] = True
                 iter_node = iter_node['metadata']['parent']
 
         return None