linting, remove some unnecessary code

src/github.com/matrix-org/dendrite/cmd/dendrite-federation-sender-server/main.go

@@ -31,13 +31,6 @@ func main() {
 
 	federation := base.CreateFederationClient()
 
-	/* TODO delete
-	err = tracers.InitGlobalTracer("Dendrite - Federation Sender")
-	if err != nil {
-		log.WithError(err).Fatalf("Failed to start tracer")
-	}
-	*/
-
 	_, _, query := base.CreateHTTPRoomserverAPIs()
 
 	federationsender.SetupFederationSenderComponent(

src/github.com/matrix-org/dendrite/common/httpapi.go

@@ -18,7 +18,7 @@ type statusCodeResponseWriter struct {
 	statusCode int
 }
 
-func NewStatusCodeResponseWriter(w http.ResponseWriter) *statusCodeResponseWriter {
+func newStatusCodeResponseWriter(w http.ResponseWriter) *statusCodeResponseWriter {
 	return &statusCodeResponseWriter{w, http.StatusOK}
 }
 
@@ -60,7 +60,7 @@ func MakeExternalAPI(tracer opentracing.Tracer, metricsName string, f func(*http
 		ext.HTTPMethod.Set(span, req.Method)
 
 		req = req.WithContext(opentracing.ContextWithSpan(req.Context(), span))
-		rw := NewStatusCodeResponseWriter(w)
+		rw := newStatusCodeResponseWriter(w)
 
 		h.ServeHTTP(w, req)
 		ext.HTTPStatusCode.Set(span, uint16(rw.statusCode))
@@ -91,7 +91,7 @@ func MakeInternalAPI(tracer opentracing.Tracer, metricsName string, f func(*http
 		ext.HTTPUrl.Set(span, req.URL.String())
 		ext.HTTPMethod.Set(span, req.Method)
 
-		// TODO: Do we need to do the NewStatusCodeResponseWriter stuff?
+		// TODO: Do we need to do the newStatusCodeResponseWriter stuff?
 
 		req = req.WithContext(opentracing.ContextWithSpan(req.Context(), span))
 		h.ServeHTTP(w, req)

src/github.com/matrix-org/dendrite/common/tracers.go

@@ -24,43 +24,29 @@ import (
 	jaegermetrics "github.com/uber/jaeger-lib/metrics"
 )
 
+// Tracers is a collection of Jaeger OpenTracing tracers. There is one tracer
+// per Dendrite component, and each is kept track of with a single Tracers
+// object. Upon shutdown, each tracer is closed by calling the Tracers' Close()
+// method.
 type Tracers struct {
 	cfg     *config.Dendrite
 	closers []io.Closer
 }
 
+// NoopTracers is a Tracers object that will never contain any tracers. Disables tracing.
 func NoopTracers() *Tracers {
 	return &Tracers{}
 }
 
+// NewTracers creates a new Tracers object with the given Dendrite config.
 func NewTracers(cfg *config.Dendrite) *Tracers {
 	return &Tracers{
 		cfg: cfg,
 	}
 }
 
-func (t *Tracers) InitGlobalTracer(serviceName string) error {
+// SetupNewTracer creates a new tracer and adds it to those being kept track of
-	if t.cfg == nil {
+// on the linked Tracers object.
-		return nil
-	}
-
-	// Set up GlobalTracer
-	closer, err := t.cfg.Tracing.Jaeger.InitGlobalTracer(
-		serviceName,
-		jaegerconfig.Logger(logrusLogger{logrus.StandardLogger()}),
-		jaegerconfig.Metrics(jaegermetrics.NullFactory),
-	)
-
-	if err != nil {
-		return err
-	}
-
-	t.closers = append(t.closers, closer)
-
-	return nil
-}
-
-// SetupTracing configures the opentracing using the supplied configuration.
 func (t *Tracers) SetupNewTracer(serviceName string) opentracing.Tracer {
 	if t.cfg == nil {
 		return opentracing.NoopTracer{}
@@ -81,6 +67,7 @@ func (t *Tracers) SetupNewTracer(serviceName string) opentracing.Tracer {
 	return tracer
 }
 
+// Close will close all Jaeger OpenTracing tracers associated with the Tracers object.
 func (t *Tracers) Close() error {
 	for _, c := range t.closers {
 		c.Close() // nolint: errcheck
@@ -94,10 +81,12 @@ type logrusLogger struct {
 	l *logrus.Logger
 }
 
+// Error prints an error message to the logger
 func (l logrusLogger) Error(msg string) {
 	l.l.Error(msg)
 }
 
+// Infof prints an info message with printf formatting to the logger
 func (l logrusLogger) Infof(msg string, args ...interface{}) {
 	l.l.Infof(msg, args...)
 }

src/github.com/matrix-org/dendrite/roomserver/input/input.go

@@ -95,17 +95,14 @@ func (r *RoomserverInputAPI) SetupHTTP(servMux *http.ServeMux, tracer opentracin
 	)
 }
 
+// InProcessRoomServerInput is a RoomserverInput database linked with a
+// OpenTracing tracer, providing metrics
 type InProcessRoomServerInput struct {
 	db     RoomserverInputAPI
 	tracer opentracing.Tracer
 }
 
-func NewInProcessRoomServerInput(db RoomserverInputAPI, tracer opentracing.Tracer) *InProcessRoomServerInput {
+// InputRoomEvents is a wrapper providing opentracing metrics data around room events
-	return &InProcessRoomServerInput{
-		db: db, tracer: tracer,
-	}
-}
-
 func (r *InProcessRoomServerInput) InputRoomEvents(
 	ctx context.Context,
 	request *api.InputRoomEventsRequest,

src/github.com/matrix-org/dendrite/roomserver/query/query.go

@@ -711,11 +711,14 @@ func (r *RoomserverQueryAPI) SetupHTTP(servMux *http.ServeMux, tracer opentracin
 	)
 }
 
+// InProcessRoomServerQueryAPI is a RoomserverQueryAPI database linked with a
+// OpenTracing tracer, providing metrics
 type InProcessRoomServerQueryAPI struct {
 	db     RoomserverQueryAPI
 	tracer opentracing.Tracer
 }
 
+// NewInProcessRoomServerQueryAPI creates a new InProcessRoomServerQueryAPI
 func NewInProcessRoomServerQueryAPI(db RoomserverQueryAPI, tracer opentracing.Tracer) InProcessRoomServerQueryAPI {
 	return InProcessRoomServerQueryAPI{
 		db:     db,