Add reload handler to web

cmd/prometheus/main.go

@@ -104,7 +104,11 @@ func Main() int {
 	signal.Notify(hup, syscall.SIGHUP)
 	go func() {
 		<-hupReady
-		for range hup {
+		for {
+			select {
+			case <-hup:
+			case <-webHandler.Reload():
+			}
 			reloadConfig(cfg.configFile, status, targetManager, ruleManager)
 		}
 	}()

web/web.go

@@ -61,6 +61,7 @@ type Handler struct {
 
 	router     *route.Router
 	quitCh     chan struct{}
+	reloadCh   chan bool // boolean saves as placeholder, actual value does not matter
 	options    *Options
 	statusInfo *PrometheusStatus
 
@@ -111,6 +112,7 @@ func New(st local.Storage, qe *promql.Engine, rm *rules.Manager, status *Prometh
 	h := &Handler{
 		router:     router,
 		quitCh:     make(chan struct{}),
+		reloadCh: make(chan bool),
 		options:    o,
 		statusInfo: status,
 
@@ -171,6 +173,7 @@ func New(st local.Storage, qe *promql.Engine, rm *rules.Manager, status *Prometh
 		router.Post("/-/quit", h.quit)
 	}
 
+	router.Post("/reload", h.reload)
 	router.Get("/debug/*subpath", http.DefaultServeMux.ServeHTTP)
 
 	return h
@@ -181,6 +184,11 @@ func (h *Handler) Quit() <-chan struct{} {
 	return h.quitCh
 }
 
+
+func (h *Handler) Reload() <-chan bool {
+	return h.reloadCh
+}
+
 // Run serves the HTTP endpoints.
 func (h *Handler) Run() {
 	log.Infof("Listening on %s", h.options.ListenAddress)
@@ -293,6 +301,11 @@ func (h *Handler) quit(w http.ResponseWriter, r *http.Request) {
 	close(h.quitCh)
 }
 
+func (h *Handler) reload(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "Reloading configuration file...")
+	h.reloadCh <- true
+}
+
 func (h *Handler) getTemplateFile(name string) (string, error) {
 	if h.options.UseLocalAssets {
 		file, err := ioutil.ReadFile(fmt.Sprintf("web/blob/templates/%s.html", name))