Introduce WebReporter to hold web-related options

app/api_topologies.go

@@ -548,17 +548,17 @@ func (r *Registry) RendererForTopology(topologyID string, values url.Values, rpt
 	return topology.renderer, nil, nil
 }
 
-type reporterHandler func(context.Context, Reporter, string, http.ResponseWriter, *http.Request)
+type reporterHandler func(context.Context, Reporter, http.ResponseWriter, *http.Request)
 
-func captureReporter(rep Reporter, metricsGraphURL string, f reporterHandler) CtxHandlerFunc {
+func captureReporter(rep Reporter, f reporterHandler) CtxHandlerFunc {
 	return func(ctx context.Context, w http.ResponseWriter, r *http.Request) {
-		f(ctx, rep, metricsGraphURL, w, r)
+		f(ctx, rep, w, r)
 	}
 }
 
 type rendererHandler func(context.Context, render.Renderer, render.Decorator, report.RenderContext, http.ResponseWriter, *http.Request)
 
-func (r *Registry) captureRenderer(rep Reporter, metricsGraphURL string, f rendererHandler) CtxHandlerFunc {
+func (r *Registry) captureRenderer(rep Reporter, f rendererHandler) CtxHandlerFunc {
 	return func(ctx context.Context, w http.ResponseWriter, req *http.Request) {
 		var (
 			topologyID = mux.Vars(req)["topology"]
@@ -579,6 +579,6 @@ func (r *Registry) captureRenderer(rep Reporter, metricsGraphURL string, f rende
 			respondWith(w, http.StatusInternalServerError, err)
 			return
 		}
-		f(ctx, renderer, decorator, report.RenderContext{Report: rpt, MetricsGraphURL: metricsGraphURL}, w, req)
+		f(ctx, renderer, decorator, RenderContextForReporter(rep, rpt), w, req)
 	}
 }

app/api_topology.go

@@ -56,7 +56,6 @@ func handleNode(ctx context.Context, renderer render.Renderer, decorator render.
 func handleWebsocket(
 	ctx context.Context,
 	rep Reporter,
-	metricsGraphURL string,
 	w http.ResponseWriter,
 	r *http.Request,
 ) {
@@ -124,10 +123,7 @@ func handleWebsocket(
 			log.Errorf("Error generating report: %v", err)
 			return
 		}
-		newTopo := detailed.Summaries(
-			report.RenderContext{Report: re, MetricsGraphURL: metricsGraphURL},
-			renderer.Render(re, decorator),
-		)
+		newTopo := detailed.Summaries(RenderContextForReporter(rep, re), renderer.Render(re, decorator))
 		diff := detailed.TopoDiff(previousTopo, newTopo)
 		previousTopo = newTopo
 

app/collector.go

@@ -34,6 +34,23 @@ type Reporter interface {
 	UnWait(context.Context, chan struct{})
 }
 
+// WebReporter is a reporter that creates reports whose data is eventually
+// displayed on websites. It carries fields that will be forwarded to the
+// report.RenderContext
+type WebReporter struct {
+	Reporter
+	MetricsGraphURL string
+}
+
+// RenderContextForReporter creates the rendering context for the given reporter.
+func RenderContextForReporter(rep Reporter, r report.Report) report.RenderContext {
+	rc := report.RenderContext{Report: r}
+	if wrep, ok := rep.(WebReporter); ok {
+		rc.MetricsGraphURL = wrep.MetricsGraphURL
+	}
+	return rc
+}
+
 // Adder is something that can accept reports. It's a convenient interface for
 // parts of the app, and several experimental components.  It takes the following
 // arguments:

app/router.go

@@ -91,7 +91,7 @@ func gzipHandler(h http.HandlerFunc) http.HandlerFunc {
 }
 
 // RegisterTopologyRoutes registers the various topology routes with a http mux.
-func RegisterTopologyRoutes(router *mux.Router, r Reporter, capabilities map[string]bool, metricsGraphURL string) {
+func RegisterTopologyRoutes(router *mux.Router, r Reporter, capabilities map[string]bool) {
 	get := router.Methods("GET").Subrouter()
 	get.HandleFunc("/api",
 		gzipHandler(requestContextDecorator(apiHandler(r, capabilities))))
@@ -99,15 +99,15 @@ func RegisterTopologyRoutes(router *mux.Router, r Reporter, capabilities map[str
 		gzipHandler(requestContextDecorator(topologyRegistry.makeTopologyList(r))))
 	get.
 		HandleFunc("/api/topology/{topology}",
-			gzipHandler(requestContextDecorator(topologyRegistry.captureRenderer(r, metricsGraphURL, handleTopology)))).
+			gzipHandler(requestContextDecorator(topologyRegistry.captureRenderer(r, handleTopology)))).
 		Name("api_topology_topology")
 	get.
 		HandleFunc("/api/topology/{topology}/ws",
-			requestContextDecorator(captureReporter(r, metricsGraphURL, handleWebsocket))). // NB not gzip!
+			requestContextDecorator(captureReporter(r, handleWebsocket))). // NB not gzip!
 		Name("api_topology_topology_ws")
 	get.
 		MatcherFunc(URLMatcher("/api/topology/{topology}/{id}")).HandlerFunc(
-		gzipHandler(requestContextDecorator(topologyRegistry.captureRenderer(r, metricsGraphURL, handleNode)))).
+		gzipHandler(requestContextDecorator(topologyRegistry.captureRenderer(r, handleNode)))).
 		Name("api_topology_topology_id")
 	get.HandleFunc("/api/report",
 		gzipHandler(requestContextDecorator(makeRawReportHandler(r))))

prog/app.go

@@ -61,7 +61,7 @@ func router(collector app.Collector, controlRouter app.ControlRouter, pipeRouter
 	app.RegisterReportPostHandler(collector, router)
 	app.RegisterControlRoutes(router, controlRouter)
 	app.RegisterPipeRoutes(router, pipeRouter)
-	app.RegisterTopologyRoutes(router, collector, capabilities, metricsGraphURL)
+	app.RegisterTopologyRoutes(router, app.WebReporter{Reporter: collector, MetricsGraphURL: metricsGraphURL}, capabilities)
 
 	uiHandler := http.FileServer(GetFS(externalUI))
 	router.PathPrefix("/ui").Name("static").Handler(