API changes for persistent local volumes.

Includes:
- A new volume type, LocalVolumeSource.  This only supports
file-based local volumes for now.
- New alpha annotation in PV: NodeAffinity
- Validation + tests for specifying LocalVolumeSource and PV
NodeAffinity
- Alpha feature gate

pkg/api/helper/helpers_test.go

@@ -266,3 +266,90 @@ func TestSysctlsFromPodAnnotation(t *testing.T) {
 		}
 	}
 }
+
+// TODO: remove when alpha support for topology constraints is removed
+func TestGetNodeAffinityFromAnnotations(t *testing.T) {
+	testCases := []struct {
+		annotations map[string]string
+		expectErr   bool
+	}{
+		{
+			annotations: nil,
+			expectErr:   false,
+		},
+		{
+			annotations: map[string]string{},
+			expectErr:   false,
+		},
+		{
+			annotations: map[string]string{
+				api.AlphaStorageNodeAffinityAnnotation: `{ 
+					"requiredDuringSchedulingIgnoredDuringExecution": { 
+						"nodeSelectorTerms": [ 
+							{ "matchExpressions": [
+								{ "key": "test-key1",
+								  "operator": "In",
+								  "values": ["test-value1", "test-value2"]
+								},
+								{ "key": "test-key2",
+								  "operator": "In",
+								  "values": ["test-value1", "test-value2"]
+								}
+							]}
+						]}
+					}`,
+			},
+			expectErr: false,
+		},
+		{
+			annotations: map[string]string{
+				api.AlphaStorageNodeAffinityAnnotation: `[{ 
+					"requiredDuringSchedulingIgnoredDuringExecution": { 
+						"nodeSelectorTerms": [ 
+							{ "matchExpressions": [
+								{ "key": "test-key1",
+								  "operator": "In",
+								  "values": ["test-value1", "test-value2"]
+								},
+								{ "key": "test-key2",
+								  "operator": "In",
+								  "values": ["test-value1", "test-value2"]
+								}
+							]}
+						]}
+					}]`,
+			},
+			expectErr: true,
+		},
+		{
+			annotations: map[string]string{
+				api.AlphaStorageNodeAffinityAnnotation: `{ 
+					"requiredDuringSchedulingIgnoredDuringExecution": { 
+						"nodeSelectorTerms":  
+							 "matchExpressions": [
+								{ "key": "test-key1",
+								  "operator": "In",
+								  "values": ["test-value1", "test-value2"]
+								},
+								{ "key": "test-key2",
+								  "operator": "In",
+								  "values": ["test-value1", "test-value2"]
+								}
+							]}
+						}
+					}`,
+			},
+			expectErr: true,
+		},
+	}
+
+	for i, tc := range testCases {
+		_, err := GetStorageNodeAffinityFromAnnotation(tc.annotations)
+		if err == nil && tc.expectErr {
+			t.Errorf("[%v]expected error but got none.", i)
+		}
+		if err != nil && !tc.expectErr {
+			t.Errorf("[%v]did not expect error but got: %v", i, err)
+		}
+	}
+}