web: add a reverse proxy to Grafana

cmd/serve.go

@@ -31,6 +31,7 @@ type ServeConfiguration struct {
 	GeoIP     geoip.Configuration
 	Kafka     kafka.Configuration
 	Core      core.Configuration
+	Web       web.Configuration
 }
 
 // DefaultServeConfiguration is the default configuration for the serve command.
@@ -42,6 +43,7 @@ var DefaultServeConfiguration = ServeConfiguration{
 	GeoIP:     geoip.DefaultConfiguration,
 	Kafka:     kafka.DefaultConfiguration,
 	Core:      core.DefaultConfiguration,
+	Web:       web.DefaultConfiguration,
 }
 
 type serveOptions struct {
@@ -156,7 +158,7 @@ func daemonStart(r *reporter.Reporter, config ServeConfiguration, checkOnly bool
 	if err != nil {
 		return fmt.Errorf("unable to initialize core component: %w", err)
 	}
-	webComponent, err := web.New(r, web.Dependencies{
+	webComponent, err := web.New(r, config.Web, web.Dependencies{
 		HTTP: httpComponent,
 	})
 	if err != nil {

docs/configuration.md

@@ -5,6 +5,7 @@ configured through a different section:
 
 - `reporting`: [Log and metric reporting](#reporting)
 - `http`: [Builtin HTTP server](#http)
+- `web`: [Web interface](#web)
 - `flow`: [Flow ingestion](#flow)
 - `snmp`: [SNMP poller](#snmp)
 - `geoip`: [GeoIP database](#geoip)
@@ -34,6 +35,14 @@ http:
   listen: 0.0.0.0:8000
 ```
 
+## Web
+
+The web interface presents the landing page of *Akvorado*. It also
+embeds the documentation. It accepts only the following key:
+
+- `grafanaurl` to specify the URL to Grafana and exposes it as
+  `/grafana`.
+
 ## Flow
 
 The flow component handles flow ingestion. It supports the following

docs/index.md

@@ -23,5 +23,6 @@ The embedded HTTP server serves the following endpoints:
 - [`/healthcheck`](/healthcheck){ target=http }: are we alive?
 - [`/flows`](/flows?limit=1){ target=http }: next available flow
 - [`/flow.proto`](/flow.proto){ target=http }: protocol buffers definition
+- [`/grafana`](/grafana): Grafana web interface (if configured)
 
 <iframe name="http" style="width: 100%; height: 200px; border: 0; background-color: #1111"></iframe>

web/config.go

@@ -0,0 +1,10 @@
+package web
+
+// Configuration describes the configuration for the web component.
+type Configuration struct {
+	// GrafanaURL is the URL to acess Grafana.
+	GrafanaURL string
+}
+
+// DefaultConfiguration represents the default configuration for the web exporter.
+var DefaultConfiguration = Configuration{}

web/root.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"io/fs"
 	netHTTP "net/http"
+	"net/http/httputil"
+	"net/url"
 
 	"akvorado/http"
 	"akvorado/reporter"
@@ -18,6 +20,7 @@ var rootSite embed.FS
 type Component struct {
 	r      *reporter.Reporter
 	d      *Dependencies
+	config Configuration
 }
 
 // Dependencies define the dependencies of the web component.
@@ -26,15 +29,33 @@ type Dependencies struct {
 }
 
 // New creates a new web component.
-func New(reporter *reporter.Reporter, dependencies Dependencies) (*Component, error) {
+func New(reporter *reporter.Reporter, config Configuration, dependencies Dependencies) (*Component, error) {
 	c := Component{
 		r:      reporter,
 		d:      &dependencies,
+		config: config,
 	}
 	data, err := fs.Sub(rootSite, "data")
 	if err != nil {
 		return nil, fmt.Errorf("unable to get embedded website: %w", err)
 	}
 	c.d.HTTP.AddHandler("/", netHTTP.FileServer(netHTTP.FS(data)))
+	if c.config.GrafanaURL != "" {
+		// Provide a proxy for Grafana
+		url, err := url.Parse(config.GrafanaURL)
+		if err != nil {
+			return nil, fmt.Errorf("unable to parse Grafana URL %q: %w", config.GrafanaURL, err)
+		}
+		proxy := httputil.NewSingleHostReverseProxy(url)
+		proxy.Transport = &netHTTP.Transport{
+			Proxy: nil, // Disable proxy
+		}
+		proxyHandler := netHTTP.HandlerFunc(
+			func(w netHTTP.ResponseWriter, r *netHTTP.Request) {
+				fmt.Println("hello")
+				proxy.ServeHTTP(w, r)
+			})
+		c.d.HTTP.AddHandler("/grafana/", proxyHandler)
+	}
 	return &c, nil
 }

web/root_test.go

@@ -0,0 +1,49 @@
+package web
+
+import (
+	"fmt"
+	"io/ioutil"
+	netHTTP "net/http"
+	"net/http/httptest"
+	"testing"
+
+	"akvorado/helpers"
+	"akvorado/http"
+	"akvorado/reporter"
+)
+
+func TestProxy(t *testing.T) {
+	// Mock HTTP server
+	server := httptest.NewServer(
+		netHTTP.HandlerFunc(
+			func(w netHTTP.ResponseWriter, r *netHTTP.Request) {
+				fmt.Fprintf(w, "hello world!")
+			}))
+	defer server.Close()
+
+	r := reporter.NewMock(t)
+	h := http.NewMock(t, r)
+	_, err := New(r, Configuration{
+		GrafanaURL: server.URL,
+	}, Dependencies{HTTP: h})
+	if err != nil {
+		t.Fatalf("New() error:\n%+v", err)
+	}
+
+	// Check the proxy works as expected
+	resp, err := netHTTP.Get(fmt.Sprintf("http://%s/grafana/test", h.Address))
+	if err != nil {
+		t.Fatalf("GET /grafana/test:\n%+v", err)
+	}
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatalf("GET /grafana/test: cannot read body:\n%+v", err)
+	}
+	if resp.StatusCode != 200 {
+		t.Errorf("GET /grafana/test: got status code %d, not 200", resp.StatusCode)
+	}
+	if diff := helpers.Diff(string(body), "hello world!"); diff != "" {
+		t.Errorf("GET /grafana/test (-got, +want):\n%s", diff)
+	}
+}