Add BasicAuth support into the example app

examples/instrumentation/go-synthetic/Dockerfile

@@ -4,7 +4,7 @@ COPY . ./
 
 FROM buildbase as appbase
 
-RUN CGO_ENABLED=0 go build -o go-synthetic ./examples/instrumentation/go-synthetic/main.go
+RUN CGO_ENABLED=0 go build -o go-synthetic ./examples/instrumentation/go-synthetic
 
 FROM gcr.io/distroless/static-debian11:latest
 COPY --from=appbase /app/go-synthetic /bin/go-synthetic

examples/instrumentation/go-synthetic/README.md

@@ -9,6 +9,31 @@ types (including exotic OpenMetrics types and Native Histograms).
 It's used for testing and validation purposes, but also can be used to demo and debug
 Prometheus monitoring infrastructure.
 
+## Running Locally
+
+You can run this application locally via:
+
+```bash
+go run ./examples/instrumentation/go-synthetic/
+```
+
+Then, you can access the [`/metrics`](http://localhost:8080/metrics) endpoint. For example, via `curl`:
+
+```bash
+curl localhost:8080/metrics
+```
+
+### Authorization
+
+The example application can be protected with various authorization methods:
+
+#### BasicAuth
+
+```bash
+go run ./examples/instrumentation/go-synthetic/ --basic-auth-username=admin --basic-auth-password=pw
+curl localhost:8080/metrics -u "admin:pw"
+```
+
 ## Running on Kubernetes
 
 If running managed-collection on a Kubernetes cluster, the `go-synthetic` can be

examples/instrumentation/go-synthetic/auth.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"flag"
+	"net/http"
+)
+
+type basicAuthConfig struct {
+	username string
+	password string
+}
+
+func newBasicAuthConfigFromFlags() *basicAuthConfig {
+	c := &basicAuthConfig{}
+	flag.StringVar(&c.username, "basic-auth-username", "", "BasicAuth username")
+	flag.StringVar(&c.password, "basic-auth-password", "", "BasicAuth password")
+	return c
+}
+
+func (c *basicAuthConfig) isEnabled() bool {
+	return c.username != "" || c.password != ""
+}
+
+func (c *basicAuthConfig) handle(handler http.Handler) http.Handler {
+	if !c.isEnabled() {
+		return handler
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		username, password, ok := r.BasicAuth()
+		if ok && username == c.username && password == c.password {
+			handler.ServeHTTP(w, r)
+			return
+		}
+
+		w.Header().Set("WWW-Authenticate", `Basic realm="restricted", charset="UTF-8"`)
+		http.Error(w, "Unauthorized", http.StatusUnauthorized)
+	})
+}

examples/instrumentation/go-synthetic/main.go

@@ -172,6 +172,7 @@ var (
 )
 
 func main() {
+	basicAuthConfig := newBasicAuthConfigFromFlags()
 	flag.Parse()
 
 	metrics := prometheus.NewRegistry()
@@ -217,8 +218,16 @@ func main() {
 		)
 	}
 	{
-		server := &http.Server{Addr: *addr}
-		http.Handle("/metrics", promhttp.HandlerFor(metrics, promhttp.HandlerOpts{Registry: metrics, EnableOpenMetrics: true}))
+		mux := http.NewServeMux()
+		mux.Handle("/metrics", basicAuthConfig.handle(promhttp.HandlerFor(metrics, promhttp.HandlerOpts{
+			Registry:          metrics,
+			EnableOpenMetrics: true,
+		})))
+
+		server := &http.Server{
+			Addr:    *addr,
+			Handler: mux,
+		}
 
 		g.Add(func() error {
 			return server.ListenAndServe()
@@ -251,7 +260,7 @@ func main() {
 		)
 	}
 	if err := g.Run(); err != nil {
-		log.Println("Exit with error", err)
+		log.Println("Exit with error:", err)
 		os.Exit(1)
 	}
 }