PMM-12350 Fix node type detection. (#782)

* PMM-12350 Fix node type detection.

* PMM-12350 Fix node type detection.

---------

Co-authored-by: Alex Demidoff <[email protected]>

Author: BupycHuk

exporter/exporter.go

@@ -138,11 +138,6 @@ func (e *Exporter) makeRegistry(ctx context.Context, client *mongo.Client, topol
 		e.logger.Errorf("Registry - Cannot get node type to check if this is a mongos : %s", err)
 	}
 
-	isArbiter, err := isArbiter(ctx, client)
-	if err != nil {
-		e.logger.Errorf("Registry - Cannot get arbiterOnly to check if this is arbiter role : %s", err)
-	}
-
 	// Enable collectors like collstats and indexstats depending on the number of collections
 	// present in the database.
 	limitsOk := false
@@ -168,7 +163,7 @@ func (e *Exporter) makeRegistry(ctx context.Context, client *mongo.Client, topol
 	}
 
 	// arbiter only have isMaster privileges
-	if isArbiter {
+	if nodeType == typeArbiter {
 		e.opts.EnableDBStats = false
 		e.opts.EnableDBStatsFreeStorage = false
 		e.opts.EnableCollStats = false

exporter/topology_info.go

@@ -41,6 +41,7 @@ const (
 	typeMongos      mongoDBNodeType = "mongos"
 	typeMongod      mongoDBNodeType = "mongod"
 	typeShardServer mongoDBNodeType = "shardsvr"
+	typeArbiter     mongoDBNodeType = "arbiter"
 	typeOther       mongoDBNodeType = ""
 )
 
@@ -114,14 +115,14 @@ func (t *topologyInfo) loadLabels(ctx context.Context) error {
 		t.labels[labelReplicasetName] = rs.Config.ID
 	}
 
-	isArbiter, err := isArbiter(ctx, t.client)
+	nodeType, err := getNodeType(ctx, t.client)
 	if err != nil {
 		return err
 	}
 
 	cid, err := util.ClusterID(ctx, t.client)
 	if err != nil {
-		if !isArbiter { // arbiters don't have a cluster ID
+		if nodeType != typeArbiter { // arbiters don't have a cluster ID
 			return errors.Wrapf(ErrCannotGetTopologyLabels, "error getting cluster ID: %s", err)
 		}
 	}
@@ -136,26 +137,14 @@ func (t *topologyInfo) loadLabels(ctx context.Context) error {
 	return nil
 }
 
-func isArbiter(ctx context.Context, client *mongo.Client) (bool, error) {
-	doc := struct {
-		ArbiterOnly bool `bson:"arbiterOnly"`
-	}{}
-
-	if err := client.Database("admin").RunCommand(ctx, primitive.M{"isMaster": 1}).Decode(&doc); err != nil {
-		return false, errors.Wrap(err, "cannot check if the instance is an arbiter")
-	}
-
-	return doc.ArbiterOnly, nil
-}
-
 func getNodeType(ctx context.Context, client *mongo.Client) (mongoDBNodeType, error) {
 	md := proto.MasterDoc{}
 	if err := client.Database("admin").RunCommand(ctx, primitive.M{"isMaster": 1}).Decode(&md); err != nil {
 		return "", err
 	}
 
-	if md.SetName != nil || md.Hosts != nil {
-		return typeShardServer, nil
+	if md.ArbiterOnly {
+		return typeArbiter, nil
 	} else if md.Msg == typeIsDBGrid {
 		// isdbgrid is always the msg value when calling isMaster on a mongos
 		// see http://docs.mongodb.org/manual/core/sharded-cluster-query-router/

exporter/v1_compatibility.go

@@ -814,7 +814,7 @@ func specialMetrics(ctx context.Context, client *mongo.Client, m bson.M, l *logr
 		}).Errorf("Cannot get node type: %s", err)
 	}
 
-	if nodeType == typeMongod {
+	if nodeType == typeMongod || nodeType == typeArbiter {
 		if engine, err := storageEngine(m); err != nil {
 			l.Errorf("cannot retrieve engine type: %s", err)
 		} else {
@@ -823,8 +823,8 @@ func specialMetrics(ctx context.Context, client *mongo.Client, m bson.M, l *logr
 	}
 	metrics = append(metrics, serverVersion(buildInfo))
 
-	if isArbiter, _ := isArbiter(ctx, client); isArbiter {
-		if hm := myRole(ctx, client, l); hm != nil {
+	if nodeType == typeArbiter {
+		if hm := arbiterMetrics(ctx, client, l); hm != nil {
 			metrics = append(metrics, hm...)
 		}
 	} else {
@@ -931,34 +931,32 @@ func myState(ctx context.Context, client *mongo.Client) prometheus.Metric {
 	return metric
 }
 
-// myRole returns metrics based on the role of the mongo instance.
-func myRole(ctx context.Context, client *mongo.Client, l *logrus.Logger) []prometheus.Metric {
+// arbiterMetrics returns metrics for mongoDB arbiter instances.
+func arbiterMetrics(ctx context.Context, client *mongo.Client, l *logrus.Logger) []prometheus.Metric {
 	response, err := util.MyRole(ctx, client)
 	if err != nil {
 		l.Errorf("cannot get role of the running instance: %s", err)
 		return nil
 	}
 
 	var metrics []prometheus.Metric
-	if response.ArbiterOnly {
-		createMetric := func(name, help string, value float64, labels map[string]string) {
-			const prefix = "mongodb_mongod_replset_"
-			d := prometheus.NewDesc(prefix+name, help, nil, labels)
-			metrics = append(metrics, prometheus.MustNewConstMetric(d, prometheus.GaugeValue, value))
-		}
+	createMetric := func(name, help string, value float64, labels map[string]string) {
+		const prefix = "mongodb_mongod_replset_"
+		d := prometheus.NewDesc(prefix+name, help, nil, labels)
+		metrics = append(metrics, prometheus.MustNewConstMetric(d, prometheus.GaugeValue, value))
+	}
 
-		createMetric("my_state",
-			"An integer between 0 and 10 that represents the replica state of the current member",
-			float64(ArbiterState), map[string]string{
-				"set": response.SetName,
-			})
+	createMetric("my_state",
+		"An integer between 0 and 10 that represents the replica state of the current member",
+		float64(ArbiterState), map[string]string{
+			"set": response.SetName,
+		})
 
-		createMetric("number_of_members",
-			"The number of replica set members.",
-			float64(len(response.Hosts)+len(response.Arbiters)), map[string]string{
-				"set": response.SetName,
-			})
-	}
+	createMetric("number_of_members",
+		"The number of replica set members.",
+		float64(len(response.Hosts)+len(response.Arbiters)), map[string]string{
+			"set": response.SetName,
+		})
 
 	return metrics
 }

exporter/v1_compatibility_test.go

@@ -260,7 +260,7 @@ func TestMyState(t *testing.T) {
 	}
 }
 
-func TestMyRole(t *testing.T) {
+func TestArbiterMetrics(t *testing.T) {
 	t.Parallel()
 	t.Run("correctly gets member count from arbiter node", func(t *testing.T) {
 		t.Parallel()
@@ -273,7 +273,7 @@ func TestMyRole(t *testing.T) {
 		port, err := tu.PortForContainer(containerName)
 		require.NoError(t, err)
 		client := tu.TestClient(ctx, port, t)
-		metrics := myRole(ctx, client, logger)
+		metrics := arbiterMetrics(ctx, client, logger)
 		var rsMembers dto.Metric
 		for _, m := range metrics {
 			if strings.HasPrefix(m.Desc().String(), `Desc{fqName: "mongodb_mongod_replset_number_of_members"`) {

internal/proto/proto.go

@@ -16,7 +16,8 @@
 package proto
 
 type MasterDoc struct {
-	SetName interface{} `bson:"setName"`
-	Hosts   interface{} `bson:"hosts"`
-	Msg     string      `bson:"msg"`
+	SetName     interface{} `bson:"setName"`
+	Hosts       interface{} `bson:"hosts"`
+	Msg         string      `bson:"msg"`
+	ArbiterOnly bool        `bson:"arbiterOnly"`
 }