Allow use of server status collector with new flag

This is useful when running the exporter against mongos instances where
getDiagnosticData is not available.

Author: trvrnrth

exporter/exporter.go

@@ -65,6 +65,7 @@ type Opts struct {
 	EnableDBStats          bool
 	EnableDiagnosticData   bool
 	EnableReplicasetStatus bool
+	EnableServerStatus     bool
 	EnableTopMetrics       bool
 	EnableIndexStats       bool
 	EnableCollStats        bool
@@ -168,6 +169,7 @@ func (e *Exporter) makeRegistry(ctx context.Context, client *mongo.Client, topol
 		e.opts.EnableCollStats = true
 		e.opts.EnableTopMetrics = true
 		e.opts.EnableReplicasetStatus = true
+		e.opts.EnableServerStatus = true
 		e.opts.EnableIndexStats = true
 	}
 
@@ -221,6 +223,12 @@ func (e *Exporter) makeRegistry(ctx context.Context, client *mongo.Client, topol
 		registry.MustRegister(rsgsc)
 	}
 
+	if e.opts.EnableServerStatus {
+		ssc := newServerStatusCollector(ctx, client, e.opts.Logger,
+			e.opts.CompatibleMode, topologyInfo)
+		registry.MustRegister(ssc)
+	}
+
 	return registry
 }
 
@@ -282,6 +290,8 @@ func (e *Exporter) Handler() http.Handler {
 				requestOpts.EnableDiagnosticData = true
 			case "replicasetstatus":
 				requestOpts.EnableReplicasetStatus = true
+			case "serverstatus":
+				requestOpts.EnableServerStatus = true
 			case "dbstats":
 				requestOpts.EnableDBStats = true
 			case "topmetrics":

main.go

@@ -47,6 +47,7 @@ type GlobalFlags struct {
 
 	EnableDiagnosticData   bool `name:"collector.diagnosticdata" help:"Enable collecting metrics from getDiagnosticData"`
 	EnableReplicasetStatus bool `name:"collector.replicasetstatus" help:"Enable collecting metrics from replSetGetStatus"`
+	EnableServerStatus     bool `name:"collector.serverstatus" help:"Enable collecting metrics from serverStatus"`
 	EnableDBStats          bool `name:"collector.dbstats" help:"Enable collecting metrics from dbStats"`
 	EnableTopMetrics       bool `name:"collector.topmetrics" help:"Enable collecting metrics from top admin command"`
 	EnableIndexStats       bool `name:"collector.indexstats" help:"Enable collecting metrics from $indexStats"`
@@ -125,6 +126,7 @@ func buildExporter(opts GlobalFlags) *exporter.Exporter {
 
 		EnableDiagnosticData:   opts.EnableDiagnosticData,
 		EnableReplicasetStatus: opts.EnableReplicasetStatus,
+		EnableServerStatus:     opts.EnableServerStatus,
 		EnableTopMetrics:       opts.EnableTopMetrics,
 		EnableDBStats:          opts.EnableDBStats,
 		EnableIndexStats:       opts.EnableIndexStats,