snapshot of https://github.com/mattermost/mattermost.git (master, 2026-09-16; blobs > 131072B omitted)

server/enterprise/metrics/dynamic.go

@@ -0,0 +1,81 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.enterprise for license information.
+
+package metrics
+
+import (
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// DynamicCounter provides a CounterVec that can create new counters via label values at runtime.
+// This allows applications to create counters at runtime without locking into Prometheus as the
+// metrics manager.
+type DynamicCounter struct {
+	counter *prometheus.CounterVec
+}
+
+// NewDynamicCounter creates a new dynamic counter with corresponding labels.
+func NewDynamicCounter(opts prometheus.CounterOpts, labels ...string) *DynamicCounter {
+	return &DynamicCounter{
+		counter: prometheus.NewCounterVec(opts, labels),
+	}
+}
+
+// GetCounter fetches a counter associated with the label values provided. An error is
+// returned if the number of values differs from the number of labels provided when
+// creating the DynamicCounter
+func (dc *DynamicCounter) GetCounter(values ...string) (prometheus.Counter, error) {
+	return dc.counter.GetMetricWithLabelValues(values...)
+}
+
+// DynamicGauge provides a GaugeVec that can create new gauges via label values at runtime.
+// This allows applications to create gauges at runtime without locking into Prometheus as the
+// metrics manager.
+type DynamicGauge struct {
+	gauge *prometheus.GaugeVec
+}
+
+// NewDynamicGauge creates a new dynamic gauge with corresponding labels.
+func NewDynamicGauge(opts prometheus.GaugeOpts, labels ...string) *DynamicGauge {
+	return &DynamicGauge{
+		gauge: prometheus.NewGaugeVec(opts, labels),
+	}
+}
+
+// GetGauge fetches a gauge associated with the label values provided. An error is
+// returned if the number of values differs from the number of labels provided when
+// creating the DynamicGauge
+func (dg *DynamicGauge) GetGauge(values ...string) (prometheus.Gauge, error) {
+	return dg.gauge.GetMetricWithLabelValues(values...)
+}
+
+// LoggerMetricsCollector provides counters for server logging.
+// Implements Logr.MetricsCollector
+type LoggerMetricsCollector struct {
+	queueGauge      *DynamicGauge
+	loggedCounters  *DynamicCounter
+	errorCounters   *DynamicCounter
+	droppedCounters *DynamicCounter
+	blockedCounters *DynamicCounter
+}
+
+func (c *LoggerMetricsCollector) QueueSizeGauge(target string) (mlog.Gauge, error) {
+	return c.queueGauge.GetGauge(target)
+}
+
+func (c *LoggerMetricsCollector) LoggedCounter(target string) (mlog.Counter, error) {
+	return c.loggedCounters.GetCounter(target)
+}
+
+func (c *LoggerMetricsCollector) ErrorCounter(target string) (mlog.Counter, error) {
+	return c.errorCounters.GetCounter(target)
+}
+
+func (c *LoggerMetricsCollector) DroppedCounter(target string) (mlog.Counter, error) {
+	return c.droppedCounters.GetCounter(target)
+}
+
+func (c *LoggerMetricsCollector) BlockedCounter(target string) (mlog.Counter, error) {
+	return c.blockedCounters.GetCounter(target)
+}

server/enterprise/metrics/histogram.go

@@ -0,0 +1,74 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.enterprise for license information.
+
+package metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+)
+
+// HistogramVec is a wrapper of prometheus.HistogramVec that stores the buckets
+// which are later passed down to WrappedObserver.
+type HistogramVec struct {
+	*prometheus.HistogramVec
+	buckets []float64
+	fqName  string
+	logger  mlog.LoggerIFace
+}
+
+// WrappedObserver is a wrapper of prometheus.Observer which addtionally
+// logs userIDs when the value exceeds or equals to the one in the highest bucket.
+type WrappedObserver struct {
+	prometheus.Observer
+	labels     prometheus.Labels
+	buckets    []float64
+	logger     mlog.LoggerIFace
+	metricName string
+	userID     string
+}
+
+// NewHistogramVec returns a custom-purpose HistogramVec.
+func NewHistogramVec(opts prometheus.HistogramOpts, labelNames []string, logger mlog.LoggerIFace) *HistogramVec {
+	if len(opts.Buckets) == 0 {
+		opts.Buckets = prometheus.DefBuckets
+	}
+	return &HistogramVec{
+		HistogramVec: prometheus.NewHistogramVec(opts, labelNames),
+		buckets:      opts.Buckets,
+		fqName:       prometheus.BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
+		logger:       logger,
+	}
+}
+
+func (v *HistogramVec) With(labels prometheus.Labels, userID string) prometheus.Observer {
+	h, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return &WrappedObserver{
+		Observer:   h,
+		labels:     labels,
+		buckets:    v.buckets,
+		logger:     v.logger,
+		metricName: v.fqName,
+		userID:     userID,
+	}
+}
+
+func (o *WrappedObserver) Observe(v float64) {
+	if v >= o.buckets[len(o.buckets)-1] {
+		fields := []mlog.Field{
+			mlog.String("metric_name", o.metricName),
+			mlog.String("user_id", o.userID),
+			mlog.Float("observed_value", v),
+			mlog.Float("highest_bucket_value", o.buckets[len(o.buckets)-1]),
+		}
+		for k, v := range o.labels {
+			fields = append(fields, mlog.String(k, v))
+		}
+		o.logger.Warn("Metric observation exceeded.", fields...)
+	}
+	o.Observer.Observe(v)
+}

server/enterprise/metrics/histogram_test.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.enterprise for license information.
+
+package metrics
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/v8/channels/api4"
+	"github.com/mattermost/mattermost/server/v8/channels/testlib"
+)
+
+func TestWrappedObserver(t *testing.T) {
+	th := api4.Setup(t)
+
+	h := NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: MetricsNamespace,
+		Subsystem: MetricsSubsystemClientsWeb,
+		Name:      "test",
+		Buckets:   []float64{0, 5, 10},
+	}, []string{"l1"}, th.TestLogger)
+
+	h.With(prometheus.Labels{"l1": "hello"}, th.BasicUser.Id).Observe(6)
+	require.NoError(t, th.TestLogger.Flush())
+	testlib.AssertNoLog(t, th.LogBuffer, mlog.LvlWarn.Name, "Metric observation exceeded.")
+
+	h.With(prometheus.Labels{"l1": "hello"}, th.BasicUser.Id).Observe(10)
+	require.NoError(t, th.TestLogger.Flush())
+	testlib.AssertLog(t, th.LogBuffer, mlog.LvlWarn.Name, "Metric observation exceeded.")
+}

server/enterprise/metrics/main_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.enterprise for license information.
+
+package metrics
+
+import (
+	"testing"
+
+	"github.com/mattermost/mattermost/server/v8/channels/api4"
+	"github.com/mattermost/mattermost/server/v8/channels/testlib"
+)
+
+var mainHelper *testlib.MainHelper
+
+func TestMain(m *testing.M) {
+	mainHelper = testlib.NewMainHelper()
+	defer mainHelper.Close()
+	api4.SetMainHelper(mainHelper)
+
+	mainHelper.Main(m)
+}

server/enterprise/metrics/metrics_test.go

@@ -0,0 +1,401 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.enterprise for license information.
+
+package metrics
+
+import (
+	"fmt"
+	"strconv"
+	"testing"
+
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/v8/channels/api4"
+	"github.com/mattermost/mattermost/server/v8/channels/app"
+	seMocks "github.com/mattermost/mattermost/server/v8/platform/services/searchengine/mocks"
+
+	"github.com/mattermost/mattermost/server/public/plugin/plugintest/mock"
+	"github.com/mattermost/mattermost/server/v8/channels/store/storetest/mocks"
+
+	"github.com/prometheus/client_golang/prometheus"
+	prometheusModels "github.com/prometheus/client_model/go"
+	"github.com/stretchr/testify/require"
+)
+
+func configureMetrics(th *api4.TestHelper) {
+	th.App.Srv().SetLicense(nil) // clear license
+	th.App.UpdateConfig(func(cfg *model.Config) {
+		*cfg.MetricsSettings.Enable = true
+		*cfg.MetricsSettings.ListenAddress = ":0"
+	})
+	th.App.Srv().SetLicense(model.NewTestLicense("metrics"))
+}
+
+func TestMetrics(t *testing.T) {
+	th := api4.SetupEnterpriseWithStoreMock(t, app.StartMetrics)
+
+	mockStore := th.App.Srv().Platform().Store.(*mocks.Store)
+	mockUserStore := mocks.UserStore{}
+	mockUserStore.On("Count", mock.Anything).Return(int64(10), nil)
+	mockPostStore := mocks.PostStore{}
+	mockPostStore.On("GetMaxPostSize").Return(model.PostMessageMaxBytesV2, nil)
+	mockSystemStore := mocks.SystemStore{}
+	mockSystemStore.On("GetByName", "UpgradedFromTE").Return(&model.System{Name: "UpgradedFromTE", Value: "false"}, nil)
+	mockSystemStore.On("GetByName", "InstallationDate").Return(&model.System{Name: "InstallationDate", Value: "10"}, nil)
+	mockStore.On("User").Return(&mockUserStore)
+	mockStore.On("Post").Return(&mockPostStore)
+	mockStore.On("System").Return(&mockSystemStore)
+	mockStore.On("GetDBSchemaVersion").Return(1, nil)
+
+	configureMetrics(th)
+	mi := th.App.Metrics()
+
+	_, ok := mi.(*MetricsInterfaceImpl)
+	require.True(t, ok, fmt.Sprintf("App.Metrics is not *MetricsInterfaceImpl, but %T", mi))
+
+	mi.IncrementHTTPRequest()
+	mi.IncrementHTTPError()
+
+	mi.IncrementPostFileAttachment(5)
+	mi.IncrementPostCreate()
+	mi.IncrementPostSentEmail()
+	mi.IncrementPostSentPush()
+	mi.IncrementPostBroadcast()
+
+	mi.IncrementLogin()
+	mi.IncrementLoginFail()
+
+	mi.IncrementClusterRequest()
+	mi.ObserveClusterRequestDuration(2.0)
+	mi.IncrementClusterEventType(model.ClusterEventPublish)
+
+	loggerCollector := mi.GetLoggerMetricsCollector()
+	g, err := loggerCollector.QueueSizeGauge("_logr")
+	require.NoError(t, err)
+	g.Set(59)
+
+	c, err := loggerCollector.LoggedCounter("_logr")
+	require.NoError(t, err)
+	c.Inc()
+
+	c, err = loggerCollector.ErrorCounter("_logr")
+	require.NoError(t, err)
+	c.Inc()
+
+	c, err = loggerCollector.DroppedCounter("_logr")
+	require.NoError(t, err)
+	c.Inc()
+
+	c, err = loggerCollector.BlockedCounter("_logr")
+	require.NoError(t, err)
+	c.Inc()
+}
+
+func TestPluginMetrics(t *testing.T) {
+	th := api4.SetupEnterprise(t, app.StartMetrics)
+
+	configureMetrics(th)
+	mi := th.App.Metrics()
+
+	miImpl, ok := mi.(*MetricsInterfaceImpl)
+	require.True(t, ok, fmt.Sprintf("App.Metrics is not *MetricsInterfaceImpl, but %T", mi))
+
+	t.Run("test ObservePluginHookDuration", func(t *testing.T) {
+		pluginID := "id_"
+		hookName := "hook_"
+		elapsed := 999.1
+		m := &prometheusModels.Metric{}
+
+		for _, success := range []bool{true, false} {
+			actualMetric, err := miImpl.PluginHookTimeHistogram.GetMetricWith(prometheus.Labels{"plugin_id": pluginID, "hook_name": hookName, "success": strconv.FormatBool(success)})
+			require.NoError(t, err)
+			require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+			require.Equal(t, uint64(0), m.Histogram.GetSampleCount())
+			require.Equal(t, 0.0, m.Histogram.GetSampleSum())
+
+			mi.ObservePluginHookDuration(pluginID, hookName, success, elapsed)
+			actualMetric, err = miImpl.PluginHookTimeHistogram.GetMetricWith(prometheus.Labels{"plugin_id": pluginID, "hook_name": hookName, "success": strconv.FormatBool(success)})
+			require.NoError(t, err)
+			require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+			require.Equal(t, uint64(1), m.Histogram.GetSampleCount())
+			require.InDelta(t, elapsed, m.Histogram.GetSampleSum(), 0.001)
+		}
+	})
+
+	t.Run("test ObservePluginAPIDuration", func(t *testing.T) {
+		pluginID := "id_"
+		apiName := "api_"
+		elapsed := 999.1
+		m := &prometheusModels.Metric{}
+
+		for _, success := range []bool{true, false} {
+			actualMetric, err := miImpl.PluginAPITimeHistogram.GetMetricWith(prometheus.Labels{"plugin_id": pluginID, "api_name": apiName, "success": strconv.FormatBool(success)})
+			require.NoError(t, err)
+			require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+			require.Equal(t, uint64(0), m.Histogram.GetSampleCount())
+			require.Equal(t, 0.0, m.Histogram.GetSampleSum())
+
+			mi.ObservePluginAPIDuration(pluginID, apiName, success, elapsed)
+			actualMetric, err = miImpl.PluginAPITimeHistogram.GetMetricWith(prometheus.Labels{"plugin_id": pluginID, "api_name": apiName, "success": strconv.FormatBool(success)})
+			require.NoError(t, err)
+			require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+			require.Equal(t, uint64(1), m.Histogram.GetSampleCount())
+			require.InDelta(t, elapsed, m.Histogram.GetSampleSum(), 0.001)
+		}
+	})
+
+	t.Run("test ObservePluginMultiHookIterationDuration", func(t *testing.T) {
+		pluginID := "id_"
+		elapsed := 999.1
+		m := &prometheusModels.Metric{}
+
+		actualMetric, err := miImpl.PluginMultiHookTimeHistogram.GetMetricWith(prometheus.Labels{"plugin_id": pluginID})
+		require.NoError(t, err)
+		require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+		require.Equal(t, uint64(0), m.Histogram.GetSampleCount())
+		require.Equal(t, 0.0, m.Histogram.GetSampleSum())
+
+		mi.ObservePluginMultiHookIterationDuration(pluginID, elapsed)
+		actualMetric, err = miImpl.PluginMultiHookTimeHistogram.GetMetricWith(prometheus.Labels{"plugin_id": pluginID})
+		require.NoError(t, err)
+		require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+		require.Equal(t, uint64(1), m.Histogram.GetSampleCount())
+		require.InDelta(t, elapsed, m.Histogram.GetSampleSum(), 0.001)
+	})
+
+	t.Run("test ObservePluginMultiHookDuration", func(t *testing.T) {
+		elapsed := 50.0
+		m := &prometheusModels.Metric{}
+
+		require.NoError(t, miImpl.PluginMultiHookServerTimeHistogram.Write(m))
+		require.InDelta(t, 0.0, m.Histogram.GetSampleSum(), 0.001)
+
+		mi.ObservePluginMultiHookDuration(elapsed)
+		require.NoError(t, miImpl.PluginMultiHookServerTimeHistogram.Write(m))
+		require.InDelta(t, elapsed, m.Histogram.GetSampleSum(), 0.001)
+	})
+}
+
+func TestMobileMetrics(t *testing.T) {
+	th := api4.SetupEnterprise(t, app.StartMetrics)
+
+	configureMetrics(th)
+	mi := th.App.Metrics()
+
+	miImpl, ok := mi.(*MetricsInterfaceImpl)
+	require.True(t, ok, fmt.Sprintf("App.Metrics is not *MetricsInterfaceImpl, but %T", mi))
+
+	ttcc := []struct {
+		name         string
+		histogramVec *prometheus.HistogramVec
+		observeFunc  func(string, float64)
+	}{
+		{
+			name:         "load duration",
+			histogramVec: miImpl.MobileClientLoadDuration,
+			observeFunc:  mi.ObserveMobileClientLoadDuration,
+		},
+		{
+			name:         "channel switch duration",
+			histogramVec: miImpl.MobileClientChannelSwitchDuration,
+			observeFunc:  mi.ObserveMobileClientChannelSwitchDuration,
+		},
+		{
+			name:         "team switch duration",
+			histogramVec: miImpl.MobileClientTeamSwitchDuration,
+			observeFunc:  mi.ObserveMobileClientTeamSwitchDuration,
+		},
+	}
+
+	for _, tc := range ttcc {
+		t.Run(tc.name, func(t *testing.T) {
+			m := &prometheusModels.Metric{}
+			elapsed := 999.1
+
+			for _, platform := range []string{"ios", "android"} {
+				actualMetric, err := tc.histogramVec.GetMetricWith(prometheus.Labels{"platform": platform})
+				require.NoError(t, err)
+				require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+				require.Equal(t, uint64(0), m.Histogram.GetSampleCount())
+				require.Equal(t, 0.0, m.Histogram.GetSampleSum())
+
+				tc.observeFunc(platform, elapsed)
+				actualMetric, err = tc.histogramVec.GetMetricWith(prometheus.Labels{"platform": platform})
+				require.NoError(t, err)
+				require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+				require.Equal(t, uint64(1), m.Histogram.GetSampleCount())
+				require.InDelta(t, elapsed, m.Histogram.GetSampleSum(), 0.001)
+			}
+		})
+	}
+}
+
+func TestExtractDBCluster(t *testing.T) {
+	testCases := []struct {
+		description         string
+		driver              string
+		connectionStr       string
+		expectedClusterName string
+	}{
+		{
+			description:         "postgres full",
+			driver:              "postgres",
+			connectionStr:       "postgres://user1234:password1234@rds-cluster-multitenant-1234-postgres.cluster-abcd.us-east-1.rds.amazonaws.com:5432/cloud?connect_timeout=10",
+			expectedClusterName: "rds-cluster-multitenant-1234-postgres",
+		},
+		{
+			description:         "postgres no credentials",
+			driver:              "postgres",
+			connectionStr:       "postgres://rds-cluster-multitenant-1234-postgres.cluster-abcd.us-east-1.rds.amazonaws.com:5432/cloud?connect_timeout=10",
+			expectedClusterName: "rds-cluster-multitenant-1234-postgres",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			host, err := extractDBCluster(tc.driver, tc.connectionStr)
+			require.NoError(t, err)
+
+			require.Equal(t, tc.expectedClusterName, host)
+		})
+	}
+}
+
+func TestSearchEngineStatusGauge(t *testing.T) {
+	th := api4.SetupEnterprise(t, app.StartMetrics)
+
+	configureMetrics(th)
+	mi := th.App.Metrics()
+
+	miImpl, ok := mi.(*MetricsInterfaceImpl)
+	require.True(t, ok, fmt.Sprintf("App.Metrics is not *MetricsInterfaceImpl, but %T", mi))
+
+	readGauge := func() float64 {
+		m := &prometheusModels.Metric{}
+		require.NoError(t, miImpl.SearchEngineStatusGauge.Write(m))
+		return m.Gauge.GetValue()
+	}
+
+	setEngine := func(t *testing.T, engine *seMocks.SearchEngineInterface) {
+		t.Helper()
+		miImpl.Platform.SearchEngine.ElasticsearchEngine = engine
+		t.Cleanup(func() {
+			miImpl.Platform.SearchEngine.ElasticsearchEngine = nil
+		})
+	}
+
+	t.Run("nil engine returns 1", func(t *testing.T) {
+		miImpl.Platform.SearchEngine.ElasticsearchEngine = nil
+		require.Equal(t, 1.0, readGauge())
+	})
+
+	t.Run("disabled engine returns 1", func(t *testing.T) {
+		esMock := &seMocks.SearchEngineInterface{}
+		esMock.On("IsEnabled").Return(false)
+		setEngine(t, esMock)
+		require.Equal(t, 1.0, readGauge())
+	})
+
+	t.Run("enabled healthy engine returns 1", func(t *testing.T) {
+		esMock := &seMocks.SearchEngineInterface{}
+		esMock.On("IsEnabled").Return(true)
+		esMock.On("IsHealthy").Return(true)
+		setEngine(t, esMock)
+		require.Equal(t, 1.0, readGauge())
+	})
+
+	t.Run("enabled unhealthy engine returns 0", func(t *testing.T) {
+		esMock := &seMocks.SearchEngineInterface{}
+		esMock.On("IsEnabled").Return(true)
+		esMock.On("IsHealthy").Return(false)
+		setEngine(t, esMock)
+		require.Equal(t, 0.0, readGauge())
+	})
+}
+
+func TestObserveClusterReliableFallbackLength(t *testing.T) {
+	th := api4.SetupEnterprise(t, app.StartMetrics)
+
+	configureMetrics(th)
+	mi := th.App.Metrics()
+
+	miImpl, ok := mi.(*MetricsInterfaceImpl)
+	require.True(t, ok, fmt.Sprintf("App.Metrics is not *MetricsInterfaceImpl, but %T", mi))
+
+	event := model.ClusterEvent("ws_event")
+	length := 42
+	m := &prometheusModels.Metric{}
+
+	t.Run("labels are correct", func(t *testing.T) {
+		_, err := miImpl.ClusterReliableFallbackLength.GetMetricWith(prometheus.Labels{"event": "x"})
+		require.NoError(t, err, "expected 'event' to be a registered label")
+		_, err = miImpl.ClusterReliableFallbackLength.GetMetricWith(prometheus.Labels{"wrong_label": "x"})
+		require.Error(t, err, "expected no label other than 'event' to be registered")
+	})
+
+	t.Run("metric is registered and initialized at 0", func(t *testing.T) {
+		actualMetric, err := miImpl.ClusterReliableFallbackLength.GetMetricWith(prometheus.Labels{"event": string(event)})
+		require.NoError(t, err)
+		require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+		require.Equal(t, uint64(0), m.Histogram.GetSampleCount())
+		require.Equal(t, 0.0, m.Histogram.GetSampleSum())
+	})
+
+	t.Run("metric can be observed and the registered value is correct", func(t *testing.T) {
+		mi.ObserveClusterReliableFallbackLength(event, length)
+
+		actualMetric, err := miImpl.ClusterReliableFallbackLength.GetMetricWith(prometheus.Labels{"event": string(event)})
+		require.NoError(t, err)
+		require.NoError(t, actualMetric.(prometheus.Histogram).Write(m))
+		require.Equal(t, uint64(1), m.Histogram.GetSampleCount())
+		require.InDelta(t, float64(length), m.Histogram.GetSampleSum(), 0.001)
+	})
+}
+
+func TestMergeLabels(t *testing.T) {
+	t.Run("combines both maps", func(t *testing.T) {
+		got := mergeLabels(map[string]string{"a": "1"}, map[string]string{"b": "2"})
+		require.Equal(t, prometheus.Labels{"a": "1", "b": "2"}, got)
+	})
+
+	t.Run("extra takes precedence over base", func(t *testing.T) {
+		got := mergeLabels(map[string]string{"a": "1"}, map[string]string{"a": "2"})
+		require.Equal(t, prometheus.Labels{"a": "2"}, got)
+	})
+
+	t.Run("handles nil maps", func(t *testing.T) {
+		require.Equal(t, prometheus.Labels{}, mergeLabels(nil, nil))
+	})
+}
+
+func TestServerInfo(t *testing.T) {
+	th := api4.SetupEnterprise(t, app.StartMetrics)
+
+	configureMetrics(th)
+	mi := th.App.Metrics()
+
+	miImpl, ok := mi.(*MetricsInterfaceImpl)
+	require.True(t, ok, fmt.Sprintf("App.Metrics is not *MetricsInterfaceImpl, but %T", mi))
+
+	m := &prometheusModels.Metric{}
+	require.NoError(t, miImpl.ServerInfo.Write(m))
+
+	t.Run("gauge value is always 1", func(t *testing.T) {
+		require.Equal(t, 1.0, m.Gauge.GetValue())
+	})
+
+	t.Run("carries the build information as labels", func(t *testing.T) {
+		labels := map[string]string{}
+		for _, pair := range m.GetLabel() {
+			labels[pair.GetName()] = pair.GetValue()
+		}
+		for key, want := range map[string]string{
+			"version":               model.CurrentVersion,
+			"build_number":          model.BuildNumber,
+			"build_hash":            model.BuildHash,
+			"build_hash_enterprise": model.BuildHashEnterprise,
+		} {
+			require.Contains(t, labels, key)
+			require.Equal(t, want, labels[key])
+		}
+	})
+}