Merge pull request #864 from prometheus/configurable-scheme

Consolidate external reachability flags into one.

cmd/prometheus/config.go

@@ -17,6 +17,7 @@ import (
 	"flag"
 	"fmt"
 	"net"
+	"net/url"
 	"os"
 	"strings"
 	"text/template"
@@ -68,17 +69,13 @@ func init() {
 	)
 
 	// Web.
-	cfg.fs.StringVar(
-		&cfg.web.PathPrefix, "web.path-prefix", "",
-		"Prefix for all web paths.",
-	)
 	cfg.fs.StringVar(
 		&cfg.web.ListenAddress, "web.listen-address", ":9090",
 		"Address to listen on for the web interface, API, and telemetry.",
 	)
 	cfg.fs.StringVar(
-		&cfg.web.Hostname, "web.hostname", "",
-		"Hostname on which the server is available.",
+		&cfg.prometheusURL, "web.external-url", "",
+		"The URL under which Prometheus is externally reachable (for example, if Prometheus is served via a reverse proxy). Used for generating relative and absolute links back to Prometheus itself. If omitted, relevant URL components will be derived automatically.",
 	)
 	cfg.fs.StringVar(
 		&cfg.web.MetricsPath, "web.telemetry-path", "/metrics",
@@ -98,7 +95,7 @@ func init() {
 	)
 	cfg.fs.StringVar(
 		&cfg.web.ConsoleTemplatesPath, "web.console.templates", "consoles",
-		"Path to the console template directory, available at /console.",
+		"Path to the console template directory, available at /consoles.",
 	)
 	cfg.fs.StringVar(
 		&cfg.web.ConsoleLibrariesPath, "web.console.libraries", "console_libraries",
@@ -224,24 +221,29 @@ func parse(args []string) error {
 		return err
 	}
 
-	ppref := strings.TrimRight(cfg.web.PathPrefix, "/")
-	if ppref != "" && !strings.HasPrefix(ppref, "/") {
-		ppref = "/" + ppref
-	}
-	cfg.web.PathPrefix = ppref
-
-	if cfg.web.Hostname == "" {
-		cfg.web.Hostname, err = os.Hostname()
+	if cfg.prometheusURL == "" {
+		hostname, err := os.Hostname()
 		if err != nil {
 			return err
 		}
+		_, port, err := net.SplitHostPort(cfg.web.ListenAddress)
+		if err != nil {
+			return err
+		}
+		cfg.prometheusURL = fmt.Sprintf("http://%s:%s/", hostname, port)
 	}
 
-	_, port, err := net.SplitHostPort(cfg.web.ListenAddress)
+	promURL, err := url.Parse(cfg.prometheusURL)
 	if err != nil {
 		return err
 	}
-	cfg.prometheusURL = fmt.Sprintf("http://%s:%s%s/", cfg.web.Hostname, port, cfg.web.PathPrefix)
+	cfg.web.ExternalURL = promURL
+
+	ppref := strings.TrimRight(cfg.web.ExternalURL.Path, "/")
+	if ppref != "" && !strings.HasPrefix(ppref, "/") {
+		ppref = "/" + ppref
+	}
+	cfg.web.ExternalURL.Path = ppref
 
 	return nil
 }

cmd/prometheus/main.go

@@ -75,8 +75,7 @@ func Main() int {
 		SampleAppender:      sampleAppender,
 		NotificationHandler: notificationHandler,
 		QueryEngine:         queryEngine,
-		PrometheusURL:       cfg.prometheusURL,
-		PathPrefix:          cfg.web.PathPrefix,
+		ExternalURL:         cfg.web.ExternalURL,
 	})
 
 	flags := map[string]string{}

rules/manager.go

@@ -16,8 +16,8 @@ package rules
 import (
 	"fmt"
 	"io/ioutil"
+	"net/url"
 	"path/filepath"
-	"strings"
 	"sync"
 	"time"
 
@@ -103,8 +103,7 @@ type Manager struct {
 	sampleAppender      storage.SampleAppender
 	notificationHandler *notification.NotificationHandler
 
-	prometheusURL string
-	pathPrefix    string
+	externalURL *url.URL
 }
 
 // ManagerOptions bundles options for the Manager.
@@ -115,8 +114,7 @@ type ManagerOptions struct {
 	NotificationHandler *notification.NotificationHandler
 	SampleAppender      storage.SampleAppender
 
-	PrometheusURL string
-	PathPrefix    string
+	ExternalURL *url.URL
 }
 
 // NewManager returns an implementation of Manager, ready to be started
@@ -130,7 +128,7 @@ func NewManager(o *ManagerOptions) *Manager {
 		sampleAppender:      o.SampleAppender,
 		queryEngine:         o.QueryEngine,
 		notificationHandler: o.NotificationHandler,
-		prometheusURL:       o.PrometheusURL,
+		externalURL:         o.ExternalURL,
 	}
 	return manager
 }
@@ -211,7 +209,7 @@ func (m *Manager) queueAlertNotifications(rule *AlertingRule, timestamp clientmo
 		defs := "{{$labels := .Labels}}{{$value := .Value}}"
 
 		expand := func(text string) string {
-			tmpl := template.NewTemplateExpander(defs+text, "__alert_"+rule.Name(), tmplData, timestamp, m.queryEngine, m.pathPrefix)
+			tmpl := template.NewTemplateExpander(defs+text, "__alert_"+rule.Name(), tmplData, timestamp, m.queryEngine, m.externalURL.Path)
 			result, err := tmpl.Expand()
 			if err != nil {
 				result = err.Error()
@@ -230,7 +228,7 @@ func (m *Manager) queueAlertNotifications(rule *AlertingRule, timestamp clientmo
 			Value:        aa.Value,
 			ActiveSince:  aa.ActiveSince.Time(),
 			RuleString:   rule.String(),
-			GeneratorURL: m.prometheusURL + strings.TrimLeft(strutil.GraphLinkForExpression(rule.vector.String()), "/"),
+			GeneratorURL: m.externalURL.String() + strutil.GraphLinkForExpression(rule.vector.String()),
 		})
 	}
 	m.notificationHandler.SubmitReqs(notifications)

web/blob/templates/_base.html

@@ -33,7 +33,7 @@
         </div>
         <div id="navbar" class="navbar-collapse collapse">
           <ul class="nav navbar-nav navbar-left">
-            {{$consoles := getConsoles}}
+            {{$consoles := consolesPath}}
             {{if $consoles}}
             <li><a href="{{$consoles}}">Consoles</a></li>
             {{ end }}

web/web.go

@@ -18,12 +18,12 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net"
 	"net/http"
 	"net/url"
 	"os"
 	"path/filepath"
 	"sort"
-	"strings"
 	"sync"
 	"time"
 
@@ -93,9 +93,8 @@ func (s *PrometheusStatus) ApplyConfig(conf *config.Config) bool {
 
 // Options for the web Handler.
 type Options struct {
-	PathPrefix           string
 	ListenAddress        string
-	Hostname             string
+	ExternalURL          *url.URL
 	MetricsPath          string
 	UseLocalAssets       bool
 	UserAssetsPath       string
@@ -131,12 +130,12 @@ func New(st local.Storage, qe *promql.Engine, rm *rules.Manager, status *Prometh
 		},
 	}
 
-	if o.PathPrefix != "" {
+	if o.ExternalURL.Path != "" {
 		// If the prefix is missing for the root path, prepend it.
 		router.Get("/", func(w http.ResponseWriter, r *http.Request) {
-			http.Redirect(w, r, o.PathPrefix, http.StatusFound)
+			http.Redirect(w, r, o.ExternalURL.Path, http.StatusFound)
 		})
-		router = router.WithPrefix(o.PathPrefix)
+		router = router.WithPrefix(o.ExternalURL.Path)
 	}
 
 	instrf := prometheus.InstrumentHandlerFunc
@@ -248,7 +247,7 @@ func (h *Handler) consoles(w http.ResponseWriter, r *http.Request) {
 		Path:      name,
 	}
 
-	tmpl := template.NewTemplateExpander(string(text), "__console_"+name, data, clientmodel.Now(), h.queryEngine, h.options.PathPrefix)
+	tmpl := template.NewTemplateExpander(string(text), "__console_"+name, data, clientmodel.Now(), h.queryEngine, h.options.ExternalURL.Path)
 	filenames, err := filepath.Glob(h.options.ConsoleLibrariesPath + "/*.lib")
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
@@ -308,13 +307,13 @@ func (h *Handler) getTemplateFile(name string) (string, error) {
 	return string(file), nil
 }
 
-func (h *Handler) getConsoles() string {
+func (h *Handler) consolesPath() string {
 	if _, err := os.Stat(h.options.ConsoleTemplatesPath + "/index.html"); !os.IsNotExist(err) {
-		return h.options.PathPrefix + "/consoles/index.html"
+		return h.options.ExternalURL.Path + "/consoles/index.html"
 	}
 	if h.options.UserAssetsPath != "" {
 		if _, err := os.Stat(h.options.UserAssetsPath + "/index.html"); !os.IsNotExist(err) {
-			return h.options.PathPrefix + "/user/index.html"
+			return h.options.ExternalURL.Path + "/user/index.html"
 		}
 	}
 	return ""
@@ -332,17 +331,11 @@ func (h *Handler) getTemplate(name string) (string, error) {
 	return baseTmpl + pageTmpl, nil
 }
 
-func (h *Handler) executeTemplate(w http.ResponseWriter, name string, data interface{}) {
-	text, err := h.getTemplate(name)
-	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-	}
-
-	tmpl := template.NewTemplateExpander(text, name, data, clientmodel.Now(), h.queryEngine, h.options.PathPrefix)
-	tmpl.Funcs(template_text.FuncMap{
-		"since":       time.Since,
-		"getConsoles": h.getConsoles,
-		"pathPrefix":  func() string { return h.options.PathPrefix },
+func tmplFuncs(consolesPath string, opts *Options) template_text.FuncMap {
+	return template_text.FuncMap{
+		"since":        time.Since,
+		"consolesPath": func() string { return consolesPath },
+		"pathPrefix":   func() string { return opts.ExternalURL.Path },
 		"stripLabels": func(lset clientmodel.LabelSet, labels ...clientmodel.LabelName) clientmodel.LabelSet {
 			for _, ln := range labels {
 				delete(lset, ln)
@@ -350,9 +343,39 @@ func (h *Handler) executeTemplate(w http.ResponseWriter, name string, data inter
 			return lset
 		},
 		"globalURL": func(u *url.URL) *url.URL {
+			host, port, err := net.SplitHostPort(u.Host)
+			if err != nil {
+				return u
+			}
 			for _, lhr := range localhostRepresentations {
-				if strings.HasPrefix(u.Host, lhr+":") {
-					u.Host = strings.Replace(u.Host, lhr+":", h.options.Hostname+":", 1)
+				if host == lhr {
+					_, ownPort, err := net.SplitHostPort(opts.ListenAddress)
+					if err != nil {
+						return u
+					}
+
+					if port == ownPort {
+						// Only in the case where the target is on localhost and its port is
+						// the same as the one we're listening on, we know for sure that
+						// we're monitoring our own process and that we need to change the
+						// scheme, hostname, and port to the externally reachable ones as
+						// well. We shouldn't need to touch the path at all, since if a
+						// path prefix is defined, the path under which we scrape ourselves
+						// should already contain the prefix.
+						u.Scheme = opts.ExternalURL.Scheme
+						u.Host = opts.ExternalURL.Host
+					} else {
+						// Otherwise, we only know that localhost is not reachable
+						// externally, so we replace only the hostname by the one in the
+						// external URL. It could be the wrong hostname for the service on
+						// this port, but it's still the best possible guess.
+						host, _, err := net.SplitHostPort(opts.ExternalURL.Host)
+						if err != nil {
+							return u
+						}
+						u.Host = host + ":" + port
+					}
+					break
 				}
 			}
 			return u
@@ -379,7 +402,17 @@ func (h *Handler) executeTemplate(w http.ResponseWriter, name string, data inter
 				panic("unknown alert state")
 			}
 		},
-	})
+	}
+}
+
+func (h *Handler) executeTemplate(w http.ResponseWriter, name string, data interface{}) {
+	text, err := h.getTemplate(name)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+	}
+
+	tmpl := template.NewTemplateExpander(text, name, data, clientmodel.Now(), h.queryEngine, h.options.ExternalURL.Path)
+	tmpl.Funcs(tmplFuncs(h.consolesPath(), h.options))
 
 	result, err := tmpl.ExpandHTML(nil)
 	if err != nil {