Adding web.external-url and web.route-prefix flags

go.mod

@@ -6,10 +6,11 @@ require (
 	github.com/go-kit/kit v0.8.0
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/miekg/dns v1.1.14
-	github.com/pkg/errors v0.8.1 // indirect
+	github.com/pkg/errors v0.8.1
 	github.com/prometheus/client_golang v1.0.0
 	github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90
 	github.com/prometheus/common v0.6.0
+	github.com/stretchr/testify v1.3.0
 	golang.org/x/crypto v0.0.0-20190617133340-57b3e21c3d56 // indirect
 	golang.org/x/net v0.0.0-20190613194153-d28f0bde5980
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58 // indirect

main.go

@@ -18,16 +18,20 @@ import (
 	"context"
 	"fmt"
 	"html"
+	"net"
 	"net/http"
 	_ "net/http/pprof"
+	"net/url"
 	"os"
 	"os/signal"
 	"strconv"
+	"strings"
 	"syscall"
 	"time"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
+	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/common/expfmt"
@@ -51,6 +55,8 @@ var (
 	timeoutOffset = kingpin.Flag("timeout-offset", "Offset to subtract from timeout in seconds.").Default("0.5").Float64()
 	configCheck   = kingpin.Flag("config.check", "If true validate the config file and then exit.").Default().Bool()
 	historyLimit  = kingpin.Flag("history.limit", "The maximum amount of items to keep in the history.").Default("100").Uint()
+	externalURL   = kingpin.Flag("web.external-url", "The URL under which Blackbox exporter is externally reachable (for example, if Blackbox exporter is served via a reverse proxy). Used for generating relative and absolute links back to Blackbox exporter itself. If the URL has a path portion, it will be used to prefix all HTTP endpoints served by Blackbox exporter. If omitted, relevant URL components will be derived automatically.").PlaceHolder("<url>").String()
+	routePrefix   = kingpin.Flag("web.route-prefix", "Prefix for the internal routes of web endpoints. Defaults to path of --web.external-url.").PlaceHolder("<path>").String()
 
 	Probers = map[string]prober.ProbeFn{
 		"http": prober.ProbeHTTP,
@@ -217,6 +223,25 @@ func run() int {
 
 	level.Info(logger).Log("msg", "Loaded config file")
 
+	// Infer or set Blackbox exporter externalURL
+	beURL, err := extURL(logger, os.Hostname, *listenAddress, *externalURL)
+	if err != nil {
+		level.Error(logger).Log("msg", "failed to determine external URL", "err", err)
+		return 1
+	}
+	level.Debug(logger).Log("externalURL", beURL.String())
+
+	// Make routePrefix default to externalURL path if empty string.
+	if *routePrefix == "" {
+		*routePrefix = beURL.Path
+	}
+	*routePrefix = "/" + strings.Trim(*routePrefix, "/")
+	level.Debug(logger).Log("routePrefix", *routePrefix)
+
+	if *routePrefix == "/" {
+		*routePrefix = ""
+	}
+
 	hup := make(chan os.Signal, 1)
 	reloadCh := make(chan chan error)
 	signal.Notify(hup, syscall.SIGHUP)
@@ -241,7 +266,7 @@ func run() int {
 		}
 	}()
 
-	http.HandleFunc("/-/reload",
+	http.HandleFunc(fmt.Sprintf("%s/-/reload", *routePrefix),
 		func(w http.ResponseWriter, r *http.Request) {
 			if r.Method != "POST" {
 				w.WriteHeader(http.StatusMethodNotAllowed)
@@ -255,25 +280,27 @@ func run() int {
 				http.Error(w, fmt.Sprintf("failed to reload config: %s", err), http.StatusInternalServerError)
 			}
 		})
-	http.Handle("/metrics", promhttp.Handler())
-	http.HandleFunc("/probe", func(w http.ResponseWriter, r *http.Request) {
+	http.Handle(fmt.Sprintf("%s/metrics", *routePrefix), promhttp.Handler())
+	http.HandleFunc(fmt.Sprintf("%s/probe", *routePrefix), func(w http.ResponseWriter, r *http.Request) {
 		sc.Lock()
 		conf := sc.C
 		sc.Unlock()
 		probeHandler(w, r, conf, logger, rh)
 	})
-	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+	http.HandleFunc(fmt.Sprintf("%s/", *routePrefix), func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/html")
-		w.Write([]byte(`<html>
-    <head><title>Blackbox Exporter</title></head>
-    <body>
-    <h1>Blackbox Exporter</h1>
-    <p><a href="/probe?target=prometheus.io&module=http_2xx">Probe prometheus.io for http_2xx</a></p>
-    <p><a href="/probe?target=prometheus.io&module=http_2xx&debug=true">Debug probe prometheus.io for http_2xx</a></p>
-    <p><a href="/metrics">Metrics</a></p>
-    <p><a href="/config">Configuration</a></p>
-    <h2>Recent Probes</h2>
-    <table border='1'><tr><th>Module</th><th>Target</th><th>Result</th><th>Debug</th>`))
+		w.Write([]byte("<html>\n"))
+		w.Write([]byte("    <head><title>Blackbox Exporter</title></head>\n"))
+		w.Write([]byte("    <body>\n"))
+		w.Write([]byte("    <h1>Blackbox Exporter</h1>\n"))
+
+		w.Write([]byte(fmt.Sprintf("    <p><a href=\"%s/probe?target=prometheus.io&module=http_2xx\">Probe prometheus.io for http_2xx</a></p>\n", *routePrefix)))
+		w.Write([]byte(fmt.Sprintf("    <p><a href=\"%s/probe?target=prometheus.io&module=http_2xx&debug=true\">Debug probe prometheus.io for http_2xx</a></p>\n", *routePrefix)))
+		w.Write([]byte(fmt.Sprintf("    <p><a href=\"%s/metrics\">Metrics</a></p>\n", *routePrefix)))
+		w.Write([]byte(fmt.Sprintf("    <p><a href=\"%s/config\">Configuration</a></p>\n", *routePrefix)))
+
+		w.Write([]byte("    <h2>Recent Probes</h2>\n"))
+		w.Write([]byte("    <table border='1'><tr><th>Module</th><th>Target</th><th>Result</th><th>Debug</th>\n"))
 
 		results := rh.List()
 
@@ -291,7 +318,7 @@ func run() int {
     </html>`))
 	})
 
-	http.HandleFunc("/logs", func(w http.ResponseWriter, r *http.Request) {
+	http.HandleFunc(fmt.Sprintf("%s/logs", *routePrefix), func(w http.ResponseWriter, r *http.Request) {
 		id, err := strconv.ParseInt(r.URL.Query().Get("id"), 10, 64)
 		if err != nil {
 			http.Error(w, "Invalid probe id", 500)
@@ -306,7 +333,7 @@ func run() int {
 		w.Write([]byte(result.debugOutput))
 	})
 
-	http.HandleFunc("/config", func(w http.ResponseWriter, r *http.Request) {
+	http.HandleFunc(fmt.Sprintf("%s/config", *routePrefix), func(w http.ResponseWriter, r *http.Request) {
 		sc.RLock()
 		c, err := yaml.Marshal(sc.C)
 		sc.RUnlock()
@@ -366,3 +393,37 @@ func getTimeout(r *http.Request, module config.Module, offset float64) (timeoutS
 
 	return timeoutSeconds, nil
 }
+
+func extURL(logger log.Logger, hostnamef func() (string, error), listen, external string) (*url.URL, error) {
+	if external == "" {
+		hostname, err := hostnamef()
+		if err != nil {
+			return nil, err
+		}
+		_, port, err := net.SplitHostPort(listen)
+		if err != nil {
+			return nil, err
+		}
+		if port == "" {
+			level.Warn(logger).Log("msg", "no port found for listen address", "address", listen)
+		}
+
+		external = fmt.Sprintf("http://%s:%s/", hostname, port)
+	}
+
+	u, err := url.Parse(external)
+	if err != nil {
+		return nil, err
+	}
+	if u.Scheme != "http" && u.Scheme != "https" {
+		return nil, errors.Errorf("%q: invalid %q scheme, only 'http' and 'https' are supported", u.String(), u.Scheme)
+	}
+
+	ppref := strings.TrimRight(u.Path, "/")
+	if ppref != "" && !strings.HasPrefix(ppref, "/") {
+		ppref = "/" + ppref
+	}
+	u.Path = ppref
+
+	return u, nil
+}

main_test.go

@@ -15,12 +15,15 @@ package main
 
 import (
 	"bytes"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/go-kit/kit/log"
 	"github.com/prometheus/client_golang/prometheus"
 	pconfig "github.com/prometheus/common/config"
@@ -137,3 +140,79 @@ func TestTimeoutIsSetCorrectly(t *testing.T) {
 		}
 	}
 }
+
+func TestExternalURL(t *testing.T) {
+	hostname := "foo"
+	for _, tc := range []struct {
+		hostnameResolver func() (string, error)
+		external         string
+		listen           string
+
+		expURL string
+		err    bool
+	}{
+		{
+			listen: ":9093",
+			expURL: "http://" + hostname + ":9093",
+		},
+		{
+			listen: "localhost:9093",
+			expURL: "http://" + hostname + ":9093",
+		},
+		{
+			listen: "localhost:",
+			expURL: "http://" + hostname + ":",
+		},
+		{
+			external: "https://host.example.com",
+			expURL:   "https://host.example.com",
+		},
+		{
+			external: "https://host.example.com/",
+			expURL:   "https://host.example.com",
+		},
+		{
+			external: "http://host.example.com/alertmanager",
+			expURL:   "http://host.example.com/alertmanager",
+		},
+		{
+			external: "http://host.example.com/alertmanager/",
+			expURL:   "http://host.example.com/alertmanager",
+		},
+		{
+			external: "http://host.example.com/////alertmanager//",
+			expURL:   "http://host.example.com/////alertmanager",
+		},
+		{
+			err: true,
+		},
+		{
+			hostnameResolver: func() (string, error) { return "", fmt.Errorf("some error") },
+			err:              true,
+		},
+		{
+			external: "://broken url string",
+			err:      true,
+		},
+		{
+			external: "host.example.com:8080",
+			err:      true,
+		},
+	} {
+		tc := tc
+		if tc.hostnameResolver == nil {
+			tc.hostnameResolver = func() (string, error) {
+				return hostname, nil
+			}
+		}
+		t.Run(fmt.Sprintf("external=%q,listen=%q", tc.external, tc.listen), func(t *testing.T) {
+			u, err := extURL(log.NewNopLogger(), tc.hostnameResolver, tc.listen, tc.external)
+			if tc.err {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+			require.Equal(t, tc.expURL, u.String())
+		})
+	}
+}