PMM-13477 a bit of refactoring.

exporter/exporter.go

@@ -145,10 +145,6 @@ func (e *Exporter) makeRegistry(ctx context.Context, client *mongo.Client, topol
 	gc := newGeneralCollector(ctx, client, nodeType, e.opts.Logger)
 	registry.MustRegister(gc)
 
-	if client == nil {
-		return registry
-	}
-
 	// Enable collectors like collstats and indexstats depending on the number of collections
 	// present in the database.
 	limitsOk := false
@@ -340,13 +336,18 @@ func (e *Exporter) Handler() http.Handler {
 			gatherers = append(gatherers, prometheus.DefaultGatherer)
 		}
 
+		var registry *prometheus.Registry
 		var ti *topologyInfo
 		if client != nil {
 			// Topology can change between requests, so we need to get it every time.
 			ti = newTopologyInfo(ctx, client, e.logger)
+			registry = e.makeRegistry(ctx, client, ti, requestOpts)
+		} else {
+			registry = prometheus.NewRegistry()
+			gc := newGeneralCollector(ctx, client, "", e.opts.Logger)
+			registry.MustRegister(gc)
 		}
 
-		registry := e.makeRegistry(ctx, client, ti, requestOpts)
 		gatherers = append(gatherers, registry)
 
 		// Delegate http serving to Prometheus client library, which will call collector.Collect.

exporter/general_collector.go

@@ -60,18 +60,17 @@ func mongodbUpMetric(ctx context.Context, client *mongo.Client, nodeType mongoDB
 	if client != nil {
 		if err := client.Ping(ctx, readpref.PrimaryPreferred()); err == nil {
 			value = 1
+			switch nodeType { //nolint:exhaustive
+			case typeMongos:
+				clusterRole = typeMongos
+			case typeArbiter:
+				clusterRole = typeArbiter
+			default:
+				clusterRole = typeMongod
+			}
 		} else {
 			log.Errorf("error while checking mongodb connection: %s. mongo_up is set to 0", err.Error())
 		}
-
-		switch nodeType { //nolint:exhaustive
-		case typeMongos:
-			clusterRole = typeMongos
-		case typeArbiter:
-			clusterRole = typeArbiter
-		default:
-			clusterRole = typeMongod
-		}
 	}
 
 	labels := map[string]string{"cluster_role": string(clusterRole)}

exporter/server.go

@@ -147,18 +147,24 @@ func OverallTargetsHandler(exporters []*Exporter, logger *logrus.Logger) http.Ha
 				}()
 			}
 
+			var registry *prometheus.Registry
 			var ti *topologyInfo
 			if client != nil {
 				// Topology can change between requests, so we need to get it every time.
 				ti = newTopologyInfo(ctx, client, e.logger)
+				registry = e.makeRegistry(ctx, client, ti, requestOpts)
+			} else {
+				registry = prometheus.NewRegistry()
+				gc := newGeneralCollector(ctx, client, "", e.opts.Logger)
+				registry.MustRegister(gc)
 			}
 
 			hostlabels := prometheus.Labels{
 				"instance": e.opts.NodeName,
 			}
 
-			registry := NewGathererWrapper(e.makeRegistry(ctx, client, ti, requestOpts), hostlabels)
-			gatherers = append(gatherers, registry)
+			gw := NewGathererWrapper(registry, hostlabels)
+			gatherers = append(gatherers, gw)
 		}
 
 		// Delegate http serving to Prometheus client library, which will call collector.Collect.