add comments for readability

Signed-off-by: Abhilash Gnan <abhilashgnan@gmail.com>

cmd/flags/admin.go

@@ -113,8 +113,10 @@ func (s *AdminServer) serveWithListener(l net.Listener) {
 	s.server = &http.Server{Handler: recoveryHandler(s.mux)}
 	s.logger.Info("Starting admin HTTP server", zap.Int("http-port", s.adminPort))
 	go func() {
-		err := s.server.Serve(l)
-		if err != nil && err != http.ErrServerClosed {
+		switch err := s.server.Serve(l); err {
+		case nil, http.ErrServerClosed:
+			// normal exit, nothing to do
+		default:
 			s.logger.Error("failed to serve", zap.Error(err))
 			s.hc.Set(healthcheck.Broken)
 		}

cmd/query/app/server.go

@@ -109,6 +109,7 @@ func (s *Server) Start() error {
 
 		switch err := s.httpServer.Serve(httpListener); err {
 		case nil, http.ErrServerClosed, cmux.ErrListenerClosed:
+			// normal exit, nothing to do
 		default:
 			s.svc.Logger.Error("Could not start HTTP server", zap.Error(err))
 		}
@@ -118,6 +119,7 @@ func (s *Server) Start() error {
 	// Start GRPC server concurrently
 	go func() {
 		s.svc.Logger.Info("Starting GRPC server", zap.Int("port", s.queryOptions.Port))
+
 		if err := s.grpcServer.Serve(grpcListener); err != nil {
 			s.svc.Logger.Error("Could not start GRPC server", zap.Error(err))
 		}
@@ -129,6 +131,7 @@ func (s *Server) Start() error {
 		s.svc.Logger.Info("Starting CMUX server", zap.Int("port", s.queryOptions.Port))
 
 		err := cmuxServer.Serve()
+		// TODO: Remove string comparision when https://github.com/soheilhy/cmux/pull/69 is merged
 		if err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
 			s.svc.Logger.Error("Could not start multiplexed server", zap.Error(err))
 		}