From 6b292822f5c6513bcb162b1b573eceae4ff91428 Mon Sep 17 00:00:00 2001
From: "Bobby (Babak) Salamat" <bsalamat@google.com>
Date: Fri, 16 Feb 2018 14:35:50 -0800
Subject: [PATCH] Pick the PriorityClass with the lowest value of priority in
 case more than one global default exists

---
 plugin/pkg/admission/priority/admission.go      | 9 +++++++--
 plugin/pkg/admission/priority/admission_test.go | 8 ++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/plugin/pkg/admission/priority/admission.go b/plugin/pkg/admission/priority/admission.go
index 5a0c98d278c..3750ec86aff 100644
--- a/plugin/pkg/admission/priority/admission.go
+++ b/plugin/pkg/admission/priority/admission.go
@@ -231,12 +231,17 @@ func (p *PriorityPlugin) getDefaultPriorityClass() (*scheduling.PriorityClass, e
 	if err != nil {
 		return nil, err
 	}
+	// In case more than one global default priority class is added as a result of a race condition,
+	// we pick the one with the lowest priority value.
+	var defaultPC *scheduling.PriorityClass
 	for _, pci := range list {
 		if pci.GlobalDefault {
-			return pci, nil
+			if defaultPC == nil || defaultPC.Value > pci.Value {
+				defaultPC = pci
+			}
 		}
 	}
-	return nil, nil
+	return defaultPC, nil
 }
 
 func (p *PriorityPlugin) getDefaultPriority() (int32, error) {
diff --git a/plugin/pkg/admission/priority/admission_test.go b/plugin/pkg/admission/priority/admission_test.go
index c9122ac63f0..06963588c61 100644
--- a/plugin/pkg/admission/priority/admission_test.go
+++ b/plugin/pkg/admission/priority/admission_test.go
@@ -189,6 +189,14 @@ func TestDefaultPriority(t *testing.T) {
 			expectedDefaultBefore: scheduling.DefaultPriorityWhenNoDefaultClassExists,
 			expectedDefaultAfter:  defaultClass1.Value,
 		},
+		{
+			name:                  "multiple default classes resolves to the minimum value among them",
+			classesBefore:         []*scheduling.PriorityClass{defaultClass1, defaultClass2},
+			classesAfter:          []*scheduling.PriorityClass{defaultClass2},
+			attributes:            admission.NewAttributesRecord(nil, nil, pcKind, "", defaultClass1.Name, pcResource, "", admission.Delete, nil),
+			expectedDefaultBefore: defaultClass1.Value,
+			expectedDefaultAfter:  defaultClass2.Value,
+		},
 		{
 			name:                  "delete default priority class",
 			classesBefore:         []*scheduling.PriorityClass{defaultClass1},