Pass /admin/metadata along to the Icecast leader

node/http.go

@@ -12,6 +12,7 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"net/http/httputil"
 	"net/url"
 	"strconv"
 	"strings"
@@ -53,6 +54,25 @@ func newHTTPHandler(n *Node, icecastPort int, domain string) http.Handler {
 		mux.Handle("/debug/", h)
 	}
 
+	// A very narrow selection of Icecast API methods is served
+	// below /admin/ and forwarded to the Icecast master via a
+	// standard httputil.ReverseProxy.
+	adminHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		leaderAddr := n.leaderAddr()
+		if leaderAddr == "" {
+			http.Error(w, "No leader", http.StatusServiceUnavailable)
+			return
+		}
+
+		rp := httputil.NewSingleHostReverseProxy(&url.URL{
+			Scheme: "http",
+			Host:   leaderAddr,
+		})
+		rp.ServeHTTP(w, r)
+	})
+	mux.Handle("/admin/metadata", adminHandler)
+	mux.Handle("/admin/killsource", adminHandler)
+
 	// Requests for /_stream/ go straight to the local Icecast.
 	proxyHandler := http.StripPrefix(autoradio.IcecastMountPrefix,
 		withMount(n, func(m *pb.Mount, w http.ResponseWriter, r *http.Request) {