fix: emit consul version metric on a regular interval (#18724)

.changelog/18724.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+telemetry: emit consul version metric on a regular interval.
+```

agent/agent.go

@@ -873,12 +873,6 @@ func (a *Agent) Start(ctx context.Context) error {
 		go m.Monitor(&lib.StopChannelContext{StopCh: a.shutdownCh})
 	}
 
-	// consul version metric with labels
-	metrics.SetGaugeWithLabels([]string{"version"}, 1, []metrics.Label{
-		{Name: "version", Value: a.config.VersionWithMetadata()},
-		{Name: "pre_release", Value: a.config.VersionPrerelease},
-	})
-
 	// start a go routine to reload config based on file watcher events
 	if a.configFileWatcher != nil {
 		a.baseDeps.Logger.Debug("starting file watcher")

agent/consul/usagemetrics/usagemetrics.go

@@ -16,6 +16,7 @@ import (
 
 	"github.com/hashicorp/consul/agent/consul/state"
 	"github.com/hashicorp/consul/logging"
+	"github.com/hashicorp/consul/version"
 )
 
 var Gauges = []prometheus.GaugeDefinition{
@@ -95,6 +96,10 @@ var Gauges = []prometheus.GaugeDefinition{
 		Name: []string{"state", "billable_service_instances"},
 		Help: "Total number of billable service instances in the local datacenter.",
 	},
+	{
+		Name: []string{"version"},
+		Help: "Represents the Consul version.",
+	},
 }
 
 type getMembersFunc func() []serf.Member
@@ -244,6 +249,7 @@ func (u *UsageMetricsReporter) runOnce() {
 	}
 
 	u.emitConfigEntryUsage(configUsage)
+	u.emitVersion()
 }
 
 func (u *UsageMetricsReporter) memberUsage() []serf.Member {
@@ -266,3 +272,26 @@ func (u *UsageMetricsReporter) memberUsage() []serf.Member {
 
 	return out
 }
+
+func (u *UsageMetricsReporter) emitVersion() {
+	// consul version metric with labels
+	metrics.SetGaugeWithLabels(
+		[]string{"version"},
+		1,
+		[]metrics.Label{
+			{Name: "version", Value: versionWithMetadata()},
+			{Name: "pre_release", Value: version.VersionPrerelease},
+		},
+	)
+}
+
+func versionWithMetadata() string {
+	vsn := version.Version
+	metadata := version.VersionMetadata
+
+	if metadata != "" {
+		vsn += "+" + metadata
+	}
+
+	return vsn
+}

agent/consul/usagemetrics/usagemetrics_ce_test.go

@@ -7,6 +7,7 @@
 package usagemetrics
 
 import (
+	"fmt"
 	"testing"
 	"time"
 
@@ -21,6 +22,7 @@ import (
 	"github.com/hashicorp/consul/agent/structs"
 	"github.com/hashicorp/consul/proto/private/pbpeering"
 	"github.com/hashicorp/consul/sdk/testutil"
+	"github.com/hashicorp/consul/version"
 )
 
 func newStateStore() (*state.Store, error) {
@@ -504,6 +506,15 @@ var baseCases = map[string]testCase{
 					{Name: "kind", Value: "control-plane-request-limit"},
 				},
 			},
+			// --- version ---
+			fmt.Sprintf("consul.usage.test.version;version=%s;pre_release=%s", versionWithMetadata(), version.VersionPrerelease): {
+				Name:  "consul.usage.test.version",
+				Value: 1,
+				Labels: []metrics.Label{
+					{Name: "version", Value: versionWithMetadata()},
+					{Name: "pre_release", Value: version.VersionPrerelease},
+				},
+			},
 		},
 		getMembersFunc: func() []serf.Member { return []serf.Member{} },
 	},
@@ -995,6 +1006,15 @@ var baseCases = map[string]testCase{
 					{Name: "kind", Value: "control-plane-request-limit"},
 				},
 			},
+			// --- version ---
+			fmt.Sprintf("consul.usage.test.version;version=%s;pre_release=%s", versionWithMetadata(), version.VersionPrerelease): {
+				Name:  "consul.usage.test.version",
+				Value: 1,
+				Labels: []metrics.Label{
+					{Name: "version", Value: versionWithMetadata()},
+					{Name: "pre_release", Value: version.VersionPrerelease},
+				},
+			},
 		},
 	},
 }

agent/consul/usagemetrics/usagemetrics_test.go

@@ -27,7 +27,7 @@ func assertEqualGaugeMaps(t *testing.T, expectedMap, foundMap map[string]metrics
 
 	for key := range foundMap {
 		if _, ok := expectedMap[key]; !ok {
-			t.Errorf("found unexpected gauge key:      %s", key)
+			t.Errorf("found unexpected gauge key: %s with value: %v", key, foundMap[key])
 		}
 	}