kata-monitor: add some links when generating pages for browsers

Add some links to rendered webpages for better user experience,
let users can jump to pages only by clicking links in browsers.

Fixes: #4061

Signed-off-by: bin <bin@hyper.sh>

src/runtime/cmd/kata-monitor/main.go

@@ -175,6 +175,15 @@ func main() {
 }
 
 func indexPage(w http.ResponseWriter, r *http.Request) {
+	htmlResponse := kataMonitor.IfReturnHTMLResponse(w, r)
+	if htmlResponse {
+		indexPageHTML(w, r)
+	} else {
+		indexPageText(w, r)
+	}
+}
+
+func indexPageText(w http.ResponseWriter, r *http.Request) {
 	w.Write([]byte("Available HTTP endpoints:\n"))
 
 	spacing := 0
@@ -184,13 +193,35 @@ func indexPage(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 	spacing = spacing + 3
+	formatter := fmt.Sprintf("%%-%ds: %%s\n", spacing)
 
-	formattedString := fmt.Sprintf("%%-%ds: %%s\n", spacing)
 	for _, endpoint := range endpoints {
-		w.Write([]byte(fmt.Sprintf(formattedString, endpoint.path, endpoint.desc)))
+		w.Write([]byte(fmt.Sprintf(formatter, endpoint.path, endpoint.desc)))
 	}
 }
 
+func indexPageHTML(w http.ResponseWriter, r *http.Request) {
+
+	w.Write([]byte("<h1>Available HTTP endpoints:</h1>\n"))
+
+	var formattedString string
+	needLinkPaths := []string{"/metrics", "/sandboxes"}
+
+	w.Write([]byte("<ul>"))
+	for _, endpoint := range endpoints {
+		formattedString = fmt.Sprintf("<b>%s</b>: %s\n", endpoint.path, endpoint.desc)
+		for _, linkPath := range needLinkPaths {
+			if linkPath == endpoint.path {
+				formattedString = fmt.Sprintf("<b><a href='%s'>%s</a></b>: %s\n", endpoint.path, endpoint.path, endpoint.desc)
+				break
+			}
+		}
+		formattedString = fmt.Sprintf("<li>%s</li>", formattedString)
+		w.Write([]byte(formattedString))
+	}
+	w.Write([]byte("</ul>"))
+}
+
 // initLog setup logger
 func initLog() {
 	kataMonitorLog := logrus.WithFields(logrus.Fields{

src/runtime/pkg/kata-monitor/metrics.go

@@ -78,6 +78,21 @@ func (km *KataMonitor) ProcessMetricsRequest(w http.ResponseWriter, r *http.Requ
 		scrapeDurationsHistogram.Observe(float64(time.Since(start).Nanoseconds() / int64(time.Millisecond)))
 	}()
 
+	// this is likely the same as `kata-runtime metrics <SANDBOX>`.
+	sandboxID, err := getSandboxIDFromReq(r)
+	if err == nil && sandboxID != "" {
+		metrics, err := GetSandboxMetrics(sandboxID)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte(err.Error()))
+			return
+		}
+		w.Write([]byte(metrics))
+		return
+	}
+
+	// if no sandbox provided, will get all sandbox's metrics.
+
 	// prepare writer for writing response.
 	contentType := expfmt.Negotiate(r.Header)
 

src/runtime/pkg/kata-monitor/monitor.go

@@ -27,6 +27,7 @@ const (
 	RuntimeCRIO                 = "cri-o"
 	fsMonitorRetryDelaySeconds  = 60
 	podCacheRefreshDelaySeconds = 5
+	contentTypeHtml             = "text/html"
 )
 
 // SetLogger sets the logger for katamonitor package.
@@ -194,7 +195,41 @@ func (km *KataMonitor) GetAgentURL(w http.ResponseWriter, r *http.Request) {
 // ListSandboxes list all sandboxes running in Kata
 func (km *KataMonitor) ListSandboxes(w http.ResponseWriter, r *http.Request) {
 	sandboxes := km.sandboxCache.getSandboxList()
+	htmlResponse := IfReturnHTMLResponse(w, r)
+	if htmlResponse {
+		listSandboxesHtml(sandboxes, w)
+	} else {
+		listSandboxesText(sandboxes, w)
+	}
+}
+
+func listSandboxesText(sandboxes []string, w http.ResponseWriter) {
 	for _, s := range sandboxes {
 		w.Write([]byte(fmt.Sprintf("%s\n", s)))
 	}
 }
+func listSandboxesHtml(sandboxes []string, w http.ResponseWriter) {
+	w.Write([]byte("<h1>Sandbox list</h1>\n"))
+	w.Write([]byte("<ul>\n"))
+	for _, s := range sandboxes {
+		w.Write([]byte(fmt.Sprintf("<li>%s: <a href='/debug/pprof/?sandbox=%s'>pprof</a>, <a href='/metrics?sandbox=%s'>metrics</a>, <a href='/agent-url?sandbox=%s'>agent-url</a></li>\n", s, s, s, s)))
+	}
+	w.Write([]byte("</ul>\n"))
+}
+
+// IfReturnHTMLResponse returns true if request accepts html response
+// NOTE: IfReturnHTMLResponse will also set response header to `text/html`
+func IfReturnHTMLResponse(w http.ResponseWriter, r *http.Request) bool {
+	accepts := r.Header["Accept"]
+	for _, accept := range accepts {
+		fields := strings.Split(accept, ",")
+		for _, field := range fields {
+			if field == contentTypeHtml {
+				w.Header().Set("Content-Type", contentTypeHtml)
+				return true
+			}
+		}
+	}
+
+	return false
+}

src/runtime/pkg/kata-monitor/pprof.go

@@ -55,8 +55,10 @@ func (km *KataMonitor) proxyRequest(w http.ResponseWriter, r *http.Request) {
 	}
 
 	uri := fmt.Sprintf("http://shim%s", r.URL.String())
+	monitorLog.Debugf("proxyRequest to: %s, uri: %s", socketAddress, uri)
 	resp, err := client.Get(uri)
 	if err != nil {
+		serveError(w, http.StatusInternalServerError, fmt.Sprintf("failed to request %s through %s", uri, socketAddress))
 		return
 	}