Merge pull request #20 from booster-proj/issue/19

Add metrics.json endpoint. Add configurable prometheusPort config field

booster.go

@@ -25,15 +25,6 @@ import (
 	"upspin.io/log"
 )
 
-type Config struct {
-	Version   string `json:"version"`
-	Commit    string `json:"commit"`
-	BuildTime string `json:"build_time"`
-
-	ProxyPort  int    `json:"proxy_port"`
-	ProxyProto string `json:"proxy_proto"`
-}
-
 // New returns an instance of a booster dialer.
 func New(b *core.Balancer) core.Dialer {
 	return &dialer{b}

cmd/booster/main.go

@@ -55,7 +55,8 @@ var (
 	rawProto = flag.String("proto", "socks5", "Proxy protocol used. Available protocols: http, socks5.")
 
 	// API configuration
-	apiPort = flag.Int("api-port", 7764, "API server listening port")
+	apiPort  = flag.Int("api-port", 7764, "API server listening port")
+	promPort = flag.Int("prometheus-port", 9090, "Port of a local prometheus server. Used for forwarding")
 
 	// Log configuration
 	verbose     = flag.Bool("verbose", false, "If set, makes the logger print also debug messages")
@@ -81,12 +82,13 @@ func main() {
 		log.Fatal(err)
 	}
 
-	config := booster.Config{
+	remote.StaticConf = remote.Config{
 		Version:    version,
 		Commit:     commit,
 		BuildTime:  buildTime,
 		ProxyPort:  *pPort,
 		ProxyProto: *rawProto,
+		PromPort:   *promPort,
 	}
 
 	b := new(core.Balancer)
@@ -99,7 +101,6 @@ func main() {
 	d := booster.New(b)
 
 	router := remote.NewRouter()
-	router.Config = config
 	router.Store = rs
 	router.MetricsProvider = mb
 	router.SetupRoutes()

remote/endpoints.go

@@ -19,28 +19,28 @@ package remote
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
+	"net"
 	"net/http"
+	"net/url"
 
-	"github.com/booster-proj/booster"
 	"github.com/booster-proj/booster/store"
 	"github.com/gorilla/mux"
 	"upspin.io/log"
 )
 
-func makeHealthCheckHandler(config booster.Config) func(w http.ResponseWriter, r *http.Request) {
-	return func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusOK)
-		w.Header().Set("Content-Type", "application/json")
-
-		json.NewEncoder(w).Encode(struct {
-			Alive bool `json:"alive"`
-			booster.Config
-		}{
-			Alive:  true,
-			Config: config,
-		})
-	}
+func healthCheckHandler(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	w.Header().Set("Content-Type", "application/json")
+
+	json.NewEncoder(w).Encode(struct {
+		Alive bool `json:"alive"`
+		Config
+	}{
+		Alive:  true,
+		Config: StaticConf,
+	})
 }
 
 func makeSourcesHandler(s *store.SourceStore) func(w http.ResponseWriter, r *http.Request) {
@@ -83,6 +83,8 @@ func makeBlockHandler(s *store.SourceStore) func(w http.ResponseWriter, r *http.
 			},
 		}
 
+		w.Header().Set("Content-Type", "application/json")
+
 		if r.Method == "POST" {
 			// Add a reason if available in the body.
 			var payload struct {
@@ -104,3 +106,33 @@ func makeBlockHandler(s *store.SourceStore) func(w http.ResponseWriter, r *http.
 		w.WriteHeader(http.StatusOK)
 	}
 }
+
+func metricsForwardHandler(w http.ResponseWriter, r *http.Request) {
+	oHost, _, err := net.SplitHostPort(r.Host)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusServiceUnavailable)
+		return
+	}
+
+	URL, _ := url.Parse(r.URL.String())
+	URL.Scheme = "http"
+	URL.Host = fmt.Sprintf("%s:%d", oHost, StaticConf.PromPort)
+	URL.Path = "api/v1/query"
+
+	req, err := http.NewRequest(r.Method, URL.String(), r.Body)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusServiceUnavailable)
+		return
+	}
+
+	req.Header = r.Header
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusServiceUnavailable)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	io.Copy(w, resp.Body)
+}

remote/router.go

@@ -20,15 +20,25 @@ package remote
 import (
 	"net/http"
 
-	"github.com/booster-proj/booster"
 	"github.com/booster-proj/booster/store"
 	"github.com/gorilla/mux"
 )
 
+type Config struct {
+	Version   string `json:"version"`
+	Commit    string `json:"commit"`
+	BuildTime string `json:"build_time"`
+
+	ProxyPort  int    `json:"proxy_port"`
+	ProxyProto string `json:"proxy_proto"`
+	PromPort   int    `json:"-"`
+}
+
+var StaticConf Config = Config{}
+
 type Router struct {
 	r *mux.Router
 
-	Config          booster.Config
 	Store           *store.SourceStore
 	MetricsProvider http.Handler
 }
@@ -43,7 +53,7 @@ func NewRouter() *Router {
 // properly.
 func (r *Router) SetupRoutes() {
 	router := r.r
-	router.HandleFunc("/health.json", makeHealthCheckHandler(r.Config))
+	router.HandleFunc("/health.json", healthCheckHandler)
 	if store := r.Store; store != nil {
 		router.HandleFunc("/sources.json", makeSourcesHandler(store))
 		router.HandleFunc("/sources/{name}/block.json", makeBlockHandler(store)).Methods("POST", "DELETE")
@@ -52,6 +62,7 @@ func (r *Router) SetupRoutes() {
 	if handler := r.MetricsProvider; handler != nil {
 		router.Handle("/metrics", handler)
 	}
+	router.HandleFunc("/metrics.json", metricsForwardHandler)
 	router.Use(loggingMiddleware)
 }