libbeat: monitor version (#26214) (#26222)

(cherry picked from commit 383f689)

CHANGELOG.next.asciidoc

@@ -438,6 +438,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Add new option `suffix` to `logging.files` to control how log files are rotated. {pull}25464[25464]
 - Validate that required functionality in Elasticsearch is available upon initial connection. {pull}25351[25351]
 - Improve ES output error insights. {pull}25825[25825]
+- Libbeat: report beat version to monitoring. {pull}26214[26214]
 
 *Auditbeat*
 

libbeat/cmd/instance/metrics/metrics_common.go

@@ -25,6 +25,7 @@ import (
 	"github.com/elastic/beats/v7/libbeat/logp"
 	"github.com/elastic/beats/v7/libbeat/monitoring"
 	"github.com/elastic/beats/v7/libbeat/monitoring/report/log"
+	"github.com/elastic/beats/v7/libbeat/version"
 )
 
 var (
@@ -59,4 +60,5 @@ func reportInfo(_ monitoring.Mode, V monitoring.Visitor) {
 	})
 
 	monitoring.ReportString(V, "ephemeral_id", ephemeralID.String())
+	monitoring.ReportString(V, "version", version.GetDefaultVersion())
 }

libbeat/cmd/instance/metrics/metrics_common_test.go

@@ -0,0 +1,33 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package metrics
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/elastic/beats/v7/libbeat/monitoring"
+	"github.com/elastic/beats/v7/libbeat/version"
+)
+
+func TestMonitoring(t *testing.T) {
+	metrics := monitoring.Default.GetRegistry("beat")
+	metricsSnapshot := monitoring.CollectFlatSnapshot(metrics, monitoring.Full, true)
+	assert.Equal(t, version.GetDefaultVersion(), metricsSnapshot.Strings["info.version"])
+}

libbeat/monitoring/report/log/log.go

@@ -66,6 +66,7 @@ var gauges = map[string]bool{
 // TODO: Change this when gauges are refactored, too.
 var strConsts = map[string]bool{
 	"beat.info.ephemeral_id": true,
+	"beat.info.version":      true,
 }
 
 var (