Support expvar data

cmd/rqlited/main.go

@@ -31,6 +31,7 @@ const sqliteDSN = "db.sqlite"
 var httpAddr string
 var raftAddr string
 var joinAddr string
+var expvar bool
 var dsn string
 var inMem bool
 var disRedirect bool
@@ -42,6 +43,7 @@ func init() {
 	flag.StringVar(&httpAddr, "http", "localhost:4001", "HTTP query server bind address")
 	flag.StringVar(&raftAddr, "raft", "localhost:4002", "Raft communication bind address")
 	flag.StringVar(&joinAddr, "join", "", "host:port of leader to join")
+	flag.BoolVar(&expvar, "expvar", true, "Serve expvar data on HTTP server")
 	flag.StringVar(&dsn, "dsn", "", `SQLite DSN parameters. E.g. "cache=shared&mode=memory"`)
 	flag.BoolVar(&inMem, "mem", false, "Use an in-memory database")
 	flag.BoolVar(&disRedirect, "noredir", true, "Disable leader-redirect")
@@ -104,6 +106,7 @@ func main() {
 	// Create the HTTP query server.
 	s := httpd.New(httpAddr, store)
 	s.DisableRedirect = disRedirect
+	s.Expvar = expvar
 	if err := s.Start(); err != nil {
 		log.Fatalf("failed to start HTTP server: %s", err.Error())
 

http/service.go

@@ -4,6 +4,8 @@ package http
 
 import (
 	"encoding/json"
+	"expvar"
+	"fmt"
 	"io/ioutil"
 	"net"
 	"net/http"
@@ -72,6 +74,7 @@ type Service struct {
 	start      time.Time // Start up time.
 	lastBackup time.Time // Time of last successful backup.
 
+	Expvar          bool
 	DisableRedirect bool // Disable leader-redirection.
 }
 
@@ -125,6 +128,8 @@ func (s *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		s.handleJoin(w, r)
 	case strings.HasPrefix(r.URL.Path, "/status"):
 		s.handleStatus(w, r)
+	case r.URL.Path == "/debug/vars" && s.Expvar:
+		serveExpvar(w, r)
 	default:
 		w.WriteHeader(http.StatusNotFound)
 	}
@@ -353,6 +358,21 @@ func (s *Service) Addr() net.Addr {
 	return s.ln.Addr()
 }
 
+// serveExpvar serves registered expvar information over HTTP.
+func serveExpvar(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	fmt.Fprintf(w, "{\n")
+	first := true
+	expvar.Do(func(kv expvar.KeyValue) {
+		if !first {
+			fmt.Fprintf(w, ",\n")
+		}
+		first = false
+		fmt.Fprintf(w, "%q: %s", kv.Key, kv.Value)
+	})
+	fmt.Fprintf(w, "\n}\n")
+}
+
 func writeResponse(w http.ResponseWriter, r *http.Request, j *Response) {
 	var b []byte
 	var err error