Validate resource names to pass to thresholds

This commit adds checks to only allow valid resource names for the
thresholds field, which are "cpu", "memory", and "pods" right now.

For the other valid or invalid resource names, descheduler will now
throw an error.

Also, tests have been added to test the added behavior.

fix #40

pkg/descheduler/strategies/lownodeutilization.go

@@ -77,22 +77,24 @@ func LowNodeUtilization(ds *options.DeschedulerServer, strategy api.DeschedulerS
 }
 
 func validateThresholds(thresholds api.ResourceThresholds) bool {
-	if thresholds == nil {
+	if thresholds == nil || len(thresholds) == 0 {
 		glog.V(1).Infof("no resource threshold is configured")
 		return false
 	}
-	found := false
 	for name := range thresholds {
-		if name == v1.ResourceCPU || name == v1.ResourceMemory || name == v1.ResourcePods {
-			found = true
-			break
-		}
-	}
-	if !found {
-		glog.V(1).Infof("one of cpu, memory, or pods resource threshold must be configured")
+		switch name {
+		case v1.ResourceCPU:
+			continue
+		case v1.ResourceMemory:
+			continue
+		case v1.ResourcePods:
+			continue
+		default:
+			glog.Errorf("only cpu, memory, or pods thresholds can be specified")
 			return false
 		}
-	return found
+	}
+	return true
 }
 
 //This function could be merged into above once we are clear.

pkg/descheduler/strategies/lownodeutilization_test.go

@@ -18,6 +18,9 @@ package strategies
 
 import (
 	"fmt"
+	"strings"
+	"testing"
+
 	"github.com/kubernetes-incubator/descheduler/pkg/api"
 	"github.com/kubernetes-incubator/descheduler/test"
 	"k8s.io/apimachinery/pkg/api/resource"
@@ -25,8 +28,6 @@ import (
 	core "k8s.io/client-go/testing"
 	"k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/client/clientset_generated/clientset/fake"
-	"strings"
-	"testing"
 )
 
 // TODO: Make this table driven.
@@ -109,3 +110,55 @@ func TestLowNodeUtilization(t *testing.T) {
 	}
 
 }
+
+func TestValidateThresholds(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   api.ResourceThresholds
+		succeed bool
+	}{
+		{
+			name:    "passing nil map for threshold",
+			input:   nil,
+			succeed: false,
+		},
+		{
+			name:    "passing no threshold",
+			input:   api.ResourceThresholds{},
+			succeed: false,
+		},
+		{
+			name: "passing unsupported resource name",
+			input: api.ResourceThresholds{
+				v1.ResourceCPU:     40,
+				v1.ResourceStorage: 25.5,
+			},
+			succeed: false,
+		},
+		{
+			name: "passing invalid resource name",
+			input: api.ResourceThresholds{
+				v1.ResourceCPU: 40,
+				"coolResource": 42.0,
+			},
+			succeed: false,
+		},
+		{
+			name: "passing a valid threshold with cpu, memory and pods",
+			input: api.ResourceThresholds{
+				v1.ResourceCPU:    20,
+				v1.ResourceMemory: 30,
+				v1.ResourcePods:   40,
+			},
+			succeed: true,
+		},
+	}
+
+	for _, test := range tests {
+		isValid := validateThresholds(test.input)
+
+		if isValid != test.succeed {
+			t.Errorf("expected validity of threshold: %#v\nto be %v but got %v instead", test.input, test.succeed, isValid)
+		}
+	}
+}