Add nil option for metric_spec to specify metrics to not be scraped. (kubernetes-sigs#503)

* Add nil option for metric_spec to specify metrics to not be scraped.

* Add logging when a metric is not being scraped when set as an empty string.

* Move unscraped metric setup logging to main.

* Update Dockerfile go version from 1.23 to 1.24

Author: BenjaminBraunDev

cmd/epp/main.go

@@ -163,6 +163,7 @@ func run() error {
 		setupLog.Error(err, "Failed to create metric mapping from flags.")
 		return err
 	}
+	verifyMetricMapping(*mapping, setupLog)
 
 	pmf := backendmetrics.NewPodMetricsFactory(&backendmetrics.PodMetricsClientImpl{MetricMapping: mapping}, *refreshMetricsInterval)
 	// Setup runner.
@@ -304,3 +305,16 @@ func validateFlags() error {
 
 	return nil
 }
+
+func verifyMetricMapping(mapping backendmetrics.MetricMapping, logger logr.Logger) {
+	if mapping.TotalQueuedRequests == nil {
+		logger.Info("Not scraping metric: TotalQueuedRequests")
+	}
+	if mapping.KVCacheUtilization == nil {
+		logger.Info("Not scraping metric: KVCacheUtilization")
+	}
+	if mapping.LoraRequestInfo == nil {
+		logger.Info("Not scraping metric: LoraRequestInfo")
+	}
+
+}

pkg/epp/backend/metrics/metrics_spec.go

@@ -41,6 +41,9 @@ type MetricMapping struct {
 //	"metric_name{label1=value1}"
 //	"metric_name{label1=value1,label2=value2}"
 func stringToMetricSpec(specStr string) (*MetricSpec, error) {
+	if specStr == "" {
+		return nil, nil // Allow empty strings to represent nil MetricSpecs
+	}
 	specStr = strings.TrimSpace(specStr)
 	metricName := specStr
 	labels := make(map[string]string)

pkg/epp/backend/metrics/metrics_spec_test.go

@@ -32,7 +32,7 @@ func TestStringToMetricSpec(t *testing.T) {
 			name:    "empty string",
 			input:   "",
 			want:    nil,
-			wantErr: true,
+			wantErr: false,
 		},
 		{
 			name:  "no labels",
@@ -152,21 +152,18 @@ func TestStringToMetricSpec(t *testing.T) {
 				t.Errorf("stringToMetricSpec() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
-			if tt.wantErr {
-				if got != nil { // handles if we got a nil spec and didn't expect an error
-					t.Errorf("stringToMetricSpec() = %v, want %v", got, tt.want)
-					return
-				}
-			} else {
-				if got == nil {
-					t.Fatalf("stringToMetricSpec() = got nil but wanted %v", tt.want)
+			if tt.want != nil && got != nil { // compare maps directly
+				if tt.want.Labels == nil {
+					tt.want.Labels = make(map[string]string)
 				}
 				if !reflect.DeepEqual(got.MetricName, tt.want.MetricName) {
 					t.Errorf("stringToMetricSpec() got MetricName = %v, want %v", got.MetricName, tt.want.MetricName)
 				}
 				if !reflect.DeepEqual(got.Labels, tt.want.Labels) {
 					t.Errorf("stringToMetricSpec() got Labels = %v, want %v", got.Labels, tt.want.Labels)
 				}
+			} else if tt.want != got { // handles if one is nil and the other isn't
+				t.Errorf("stringToMetricSpec() = %v, want %v", got, tt.want)
 			}
 		})
 	}