ipvs: log error if scheduler does not exist and fallback to rr

Signed-off-by: Christopher M. Luciano <cmluciano@us.ibm.com>

cmd/kube-proxy/app/server_others_test.go

@@ -151,6 +151,14 @@ func Test_getProxyMode(t *testing.T) {
 			expected:      proxyModeIPVS,
 			scheduler:     "sed",
 		},
+		{ // flag says ipvs, ipset version ok, non-existent scheduler
+			flag:          "ipvs",
+			kmods:         []string{"ip_vs", "ip_vs_rr", "ip_vs_wrr", "ip_vs_sh", "nf_conntrack", "ip_vs_sed"},
+			kernelVersion: "4.19",
+			ipsetVersion:  ipvs.MinIPSetCheckVersion,
+			expected:      proxyModeIPVS,
+			scheduler:     "foobar",
+		},
 	}
 	for i, c := range cases {
 		kcompater := &fakeKernelCompatTester{c.kernelCompat}

pkg/proxy/ipvs/proxier.go

@@ -711,7 +711,11 @@ func CanUseIPVSProxier(handle KernelHandler, ipsetver IPSetVersioner, scheduler
 	}
 	mods = utilipvs.GetRequiredIPVSModules(kernelVersion)
 	wantModules := sets.NewString()
-	mods = append(mods, utilipvs.GetRequiredSchedulerModules(scheduler))
+	schedulerMod, modNotFound := utilipvs.GetRequiredSchedulerModules(scheduler)
+	if modNotFound != nil {
+		klog.Error(modNotFound)
+	}
+	mods = append(mods, schedulerMod)
 	wantModules.Insert(mods...)
 
 	modules := wantModules.Difference(loadModules).UnsortedList()

pkg/proxy/ipvs/proxier_test.go

@@ -348,6 +348,14 @@ func TestCanUseIPVSProxier(t *testing.T) {
 			ipsetVersion:  MinIPSetCheckVersion,
 			ok:            true,
 		},
+		// case 10, non-existent scheduler, fallback to rr
+		{
+			mods:          []string{"ip_vs", "ip_vs_rr", "ip_vs_wrr", "ip_vs_sh", "nf_conntrack", "ip_vs_dh"},
+			scheduler:     "foobar",
+			kernelVersion: "4.19",
+			ipsetVersion:  MinIPSetCheckVersion,
+			ok:            true,
+		},
 	}
 
 	for i := range testCases {

pkg/util/ipvs/ipvs.go

@@ -17,6 +17,7 @@ limitations under the License.
 package ipvs
 
 import (
+	"fmt"
 	"net"
 	"strconv"
 	"strings"
@@ -149,21 +150,24 @@ func IsRsGracefulTerminationNeeded(proto string) bool {
 }
 
 // GetRequiredSchedulerModules returns the required ipvs scheduler module for configured scheduler
-func GetRequiredSchedulerModules(scheduler string) string {
+func GetRequiredSchedulerModules(scheduler string) (string, error) {
 	switch s := scheduler; s {
 	case "rr":
-		return KernelModuleIPVSRR
+		return KernelModuleIPVSRR, nil
 	case "lc":
-		return KernelModuleIPVSLC
+		return KernelModuleIPVSLC, nil
 	case "nq":
-		return KernelModuleIPVSNQ
+		return KernelModuleIPVSNQ, nil
 	case "dh":
-		return KernelModuleIPVSDH
+		return KernelModuleIPVSDH, nil
 	case "sh":
-		return KernelModuleIPVSSH
+		return KernelModuleIPVSSH, nil
 	case "sed":
-		return KernelModuleIPVSSED
+		return KernelModuleIPVSSED, nil
+	case "":
+		return KernelModuleIPVSRR, nil
 	default:
-		return KernelModuleIPVSRR
+		notFound := fmt.Errorf("ip_vs_%s is not a supported IPVS scheduler algorithm, falling back to round-robin", scheduler)
+		return KernelModuleIPVSRR, notFound
 	}
 }

pkg/util/ipvs/ipvs_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package ipvs
 
 import (
+	"fmt"
 	"net"
 	"reflect"
 	"sort"
@@ -413,3 +414,51 @@ func TestGetRequiredIPVSModules(t *testing.T) {
 		})
 	}
 }
+
+func TestGetRequiredSchedulerModules(t *testing.T) {
+	Tests := []struct {
+		name         string
+		scheduler    string
+		want         string
+		expectedErrs error
+	}{
+		{
+			name:         "scheduler explicitly set to  rr",
+			scheduler:    "rr",
+			want:         "ip_vs_rr",
+			expectedErrs: nil,
+		},
+		{
+			name:         "scheduler set to  nq",
+			scheduler:    "nq",
+			want:         "ip_vs_nq",
+			expectedErrs: nil,
+		},
+		{
+			name:         "unset scheduler",
+			scheduler:    "",
+			want:         "ip_vs_rr",
+			expectedErrs: nil,
+		},
+		{
+			name:         "invalid scheduler algorithm",
+			scheduler:    "foobar",
+			want:         "ip_vs_rr",
+			expectedErrs: fmt.Errorf("ip_vs_%s is not a supported IPVS scheduler algorithm, falling back to round-robin", "foobar"),
+		},
+	}
+
+	for _, test := range Tests {
+		t.Run(test.name, func(t *testing.T) {
+			got, err := GetRequiredSchedulerModules(test.scheduler)
+			if !reflect.DeepEqual(got, test.want) {
+				t.Fatalf("GetRequiredSchedulerModules() = testCase %v failed- expected: %s scheduler, but got: %s", test.name, test.want, got)
+			}
+			if err != nil {
+				if err.Error() != test.expectedErrs.Error() {
+					t.Fatalf("Expected error: %v, got: %v", test.expectedErrs, err.Error())
+				}
+			}
+		})
+	}
+}