Metric to expose configured network MTU

pkg/monitor/cluster/cluster.go

@@ -190,6 +190,7 @@ func NewMonitor(log *logrus.Entry, restConfig *rest.Config, oc *api.OpenShiftClu
 		mon.emitPrometheusAlerts, // at the end for now because it's the slowest/least reliable
 		mon.emitCWPStatus,
 		mon.emitClusterAuthenticationType,
+		mon.emitNetworkMTU,
 	}
 
 	return mon, nil

pkg/monitor/cluster/networkmtu.go

@@ -0,0 +1,36 @@
+package cluster
+
+// Copyright (c) Microsoft Corporation.
+// Licensed under the Apache License 2.0.
+
+import (
+	"context"
+	"strconv"
+
+	"github.com/sirupsen/logrus"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+// emitNetworkMTU collects and emits metrics related to cluster network MTU configuration
+func (mon *Monitor) emitNetworkMTU(ctx context.Context) error {
+	networkConfig, err := mon.configcli.ConfigV1().Networks().Get(ctx, "cluster", metav1.GetOptions{})
+	if err != nil {
+		return err
+	}
+
+	mtuString := strconv.Itoa(networkConfig.Status.ClusterNetworkMTU)
+
+	mon.emitGauge("network.mtu", 1, map[string]string{
+		"mtu":          mtuString,
+		"network_type": networkConfig.Spec.NetworkType,
+	})
+
+	if mon.hourlyRun {
+		mon.log.WithFields(logrus.Fields{
+			"mtu":          mtuString,
+			"network_type": networkConfig.Spec.NetworkType,
+		}).Info("network MTU configuration")
+	}
+	return nil
+}

pkg/monitor/cluster/networkmtu_test.go

@@ -0,0 +1,157 @@
+package cluster
+
+// Copyright (c) Microsoft Corporation.
+// Licensed under the Apache License 2.0.
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"go.uber.org/mock/gomock"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	configv1 "github.com/openshift/api/config/v1"
+	configfake "github.com/openshift/client-go/config/clientset/versioned/fake"
+
+	"github.com/Azure/ARO-RP/pkg/api"
+	mock_metrics "github.com/Azure/ARO-RP/pkg/util/mocks/metrics"
+	testlog "github.com/Azure/ARO-RP/test/util/log"
+)
+
+func TestEmitNetworkMTU(t *testing.T) {
+	ctx := context.Background()
+
+	tests := []struct {
+		name           string
+		oc             *api.OpenShiftCluster
+		networkConfig  *configv1.Network
+		expectedMetric metricExpectation
+	}{
+		{
+			name: "MTU 1500 cluster with OpenShiftSDN",
+			oc: &api.OpenShiftCluster{
+				Properties: api.OpenShiftClusterProperties{
+					NetworkProfile: api.NetworkProfile{
+						MTUSize: api.MTU1500,
+					},
+				},
+			},
+			networkConfig: &configv1.Network{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "cluster",
+				},
+				Spec: configv1.NetworkSpec{
+					NetworkType: "OpenShiftSDN",
+				},
+				Status: configv1.NetworkStatus{
+					ClusterNetworkMTU: 1500,
+				},
+			},
+			expectedMetric: metricExpectation{
+				name:  "network.mtu",
+				value: 1,
+				labels: map[string]string{
+					"mtu":          "1500",
+					"network_type": "OpenShiftSDN",
+				},
+			},
+		},
+		{
+			name: "MTU 1400 cluster with OVNKubernetes",
+			oc: &api.OpenShiftCluster{
+				Properties: api.OpenShiftClusterProperties{
+					NetworkProfile: api.NetworkProfile{
+						MTUSize: api.MTU1500,
+					},
+				},
+			},
+			networkConfig: &configv1.Network{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "cluster",
+				},
+				Spec: configv1.NetworkSpec{
+					NetworkType: "OVNKubernetes",
+				},
+				Status: configv1.NetworkStatus{
+					ClusterNetworkMTU: 1400,
+				},
+			},
+			expectedMetric: metricExpectation{
+				name:  "network.mtu",
+				value: 1,
+				labels: map[string]string{
+					"mtu":          "1400",
+					"network_type": "OVNKubernetes",
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			controller := gomock.NewController(t)
+			m := mock_metrics.NewMockEmitter(controller)
+			_, log := testlog.New()
+
+			configcli := configfake.NewSimpleClientset(tt.networkConfig)
+
+			mon := &Monitor{
+				oc:        tt.oc,
+				configcli: configcli,
+				m:         m,
+				log:       log,
+			}
+
+			m.EXPECT().EmitGauge(tt.expectedMetric.name, tt.expectedMetric.value, tt.expectedMetric.labels)
+
+			err := mon.emitNetworkMTU(ctx)
+			if err != nil {
+				t.Errorf("emitNetworkMTU() error = %v", err)
+			}
+		})
+	}
+}
+
+func TestEmitNetworkMTUError(t *testing.T) {
+	ctx := context.Background()
+
+	controller := gomock.NewController(t)
+	m := mock_metrics.NewMockEmitter(controller)
+	_, log := testlog.New()
+
+	oc := &api.OpenShiftCluster{
+		Properties: api.OpenShiftClusterProperties{
+			NetworkProfile: api.NetworkProfile{
+				MTUSize: api.MTU1500,
+			},
+		},
+	}
+
+	configcli := configfake.NewSimpleClientset()
+
+	mon := &Monitor{
+		oc:        oc,
+		configcli: configcli,
+		m:         m,
+		log:       log,
+	}
+
+	err := mon.emitNetworkMTU(ctx)
+	if err == nil {
+		t.Error("expected error when network config is not found, got nil")
+	}
+
+	// Assert that it's a "not found" error
+	if err != nil && !strings.Contains(err.Error(), "not found") {
+		t.Errorf("expected 'not found' error, got: %v", err)
+	}
+}
+
+// metricExpectation represents an expected metric emission
+type metricExpectation struct {
+	name   string
+	value  int64
+	labels map[string]string
+}