golang websocket memory leak

We have a websocket service based on go-socket.io( the socket.io golang implementation) and gorilla websocket, but seems have a memory leak problem. The HeapAlloc is always increase even I using the debug.FreeOSMemroy to force release the memory.

The service is very simple. It will authenticate the come in request with jwt token, if authentication is successful, then will create a go-socket.io conn based on the gorilla websocket conn. But now seems that the *net/textproto.(Reader).ReadMIMEHeader (contains in net/http.readRequest which located in net/http.(*conn).serve) took much memory which confused me, because when the request hijack to the websocket conn, the net/http.(*conn).serve goroutine will return immediately.

1. heap in-use callgraph

https://lh3.googleusercontent.com/-mm2uAP5ihFM/V9IVWSlqUFI/AAAAAAAAAFc/8lLdQ3XgKCgeuCxQN81VQ8U5mDJcQxvWQCLcB/s1600/heap_in_use.png

2. heap alloc space callgraph

https://lh3.googleusercontent.com/-zKpnnKowYcc/V9IV5Ncxs3I/AAAAAAAAAFg/hcptQ-bmiwsmRbFYnvTEB9jNylbJ8nh3gCLcB/s1600/heap_alloc.png

3. gc trace log

<pre><code>

gc 440 @51045.897s 0%: 0.034+4182+0.96 ms clock, 0.13+0/4182/12246+3.8 ms cpu, 4304->4309->4143 MB, 8266 MB goal, 4 P
scvg340: inuse: 4404, idle: 15, sys: 4419, released: 0, consumed: 4419 (MB)
GC forced
gc 441 @51170.096s 0%: 3.7+4355+1.4 ms clock, 14+2.9/4357/12795+5.8 ms cpu, 4317->4323->4158 MB, 8287 MB goal, 4 P
GC forced
gc 442 @51294.460s 0%: 0.034+3987+1.2 ms clock, 0.13+1.5/3987/11701+4.9 ms cpu, 4336->4341->4169 MB, 8316 MB goal, 4 P
scvg341: inuse: 4318, idle: 133, sys: 4451, released: 0, consumed: 4451 (MB)
GC forced
gc 443 @51418.451s 0%: 0.36+3925+0.99 ms clock, 1.4+4.0/3925/11554+3.9 ms cpu, 4350->4356->4182 MB, 8338 MB goal, 4 P
scvg342: inuse: 4363, idle: 103, sys: 4466, released: 0, consumed: 4466 (MB)
GC forced
gc 444 @51542.394s 0%: 0.042+3986+1.6 ms clock, 0.16+0/3981/11757+6.5 ms cpu, 4361->4367->4194 MB, 8365 MB goal, 4 P
scvg343: inuse: 4404, idle: 74, sys: 4478, released: 0, consumed: 4478 (MB)
GC forced
gc 445 @51666.384s 0%: 3.4+3987+1.4 ms clock, 13+2.5/3986/11747+5.7 ms cpu, 4375->4382->4208 MB, 8388 MB goal, 4 P
scvg344: inuse: 4454, idle: 39, sys: 4493, released: 0, consumed: 4493 (MB)
GC forced
gc 446 @51790.379s 0%: 0.055+4147+1.5 ms clock, 0.22+0/4139/12125+6.2 ms cpu, 4396->4402->4220 MB, 8416 MB goal, 4 P
scvg345: inuse: 4509, idle: 5, sys: 4514, released: 0, consumed: 4514 (MB)
GC forced
gc 447 @51914.542s 0%: 0.052+4205+2.1 ms clock, 0.21+1.5/4199/12348+8.5 ms cpu, 4413->4420->4234 MB, 8441 MB goal, 4 P
GC forced
gc 448 @52038.752s 0%: 2.7+4517+1.8 ms clock, 11+2.3/4517/13245+7.2 ms cpu, 4428->4436->4247 MB, 8469 MB goal, 4 P
scvg346: inuse: 4406, idle: 142, sys: 4548, released: 0, consumed: 4548 (MB)
GC forced
gc 449 @52163.276s 0%: 0.033+4206+1.3 ms clock, 0.13+0/4206/12306+5.3 ms cpu, 4442->4449->4259 MB, 8495 MB goal, 4 P
scvg347: inuse: 4452, idle: 109, sys: 4561, released: 0, consumed: 4561 (MB)
GC forced
gc 450 @52287.491s 0%: 0.044+4262+2.0 ms clock, 0.17+0/4261/12565+8.2 ms cpu, 4452->4459->4272 MB, 8519 MB goal, 4 P
scvg348: inuse: 4498, idle: 74, sys: 4572, released: 0, consumed: 4572 (MB)
GC forced
gc 451 @52411.769s 0%: 0.028+4012+2.0 ms clock, 0.11+0.066/3992/11762+8.0 ms cpu, 4471->4477->4285 MB, 8544 MB goal, 4 P
scvg349: inuse: 4550, idle: 40, sys: 4590, released: 0, consumed: 4590 (MB)

</code></pre>

4. code example

    func (c *CometServer) initHTTPServer() {
   jwtMiddleware := jwtmiddleware.New(jwtmiddleware.Options{
   SigningMethod: jwt.SigningMethodHS256,
   ValidationKeyGetter: func(token *jwt.Token) (interface{}, error) {
   return []byte(setting.JwtSecret), nil
   },
   // get token from header, querystring, and cookie
   Extractor: jwtmiddleware.FromFirst(
   jwtmiddleware.FromParameter(setting.JwtTokenQueryStringField),
   TokenFromCookie(setting.JwtTokenCookieField),
   jwtmiddleware.FromAuthHeader,
   ),
   ErrorHandler: jwtErrorHandler,
   })
   r := mux.NewRouter()
   // Must call cotext.Clear after every request follow
   r.KeepContext = true
   socketHandler := jwtMiddleware.Handler(c.socketio)
   r.Handle("/socket.io/", socketHandler)
   if setting.DEBUG {
   r.PathPrefix("/debug/").Handler(http.DefaultServeMux)
   r.PathPrefix("/").Handler(http.FileServer(http.Dir("./asset/")))
   }
   // n.UseHandler(r)
   c.httpServer = &http.Server{
   Addr:    setting.HTTPListenAddr,
   Handler: r,
   }
   

   }

   // ....
   // go-socket.io code
   // ....
   func (c *CometServer) initSocketIO() error {
   server, err := socketio.NewServer(transports)
   if err != nil {
   return err
   }

    // ....
   server.On("error", func(so socketio.Socket, err error) {
   logger := SocketLogger(so)
   logger.Error("socket connect error")
   })
   server.On("connection", func(so socketio.Socket) {
   var (
   uid   string
   exist bool
   )
   logger := SocketLogger(so)
   claim := (context.Get(so.Request(), "user")).(*jwt.Token).Claims
   // after get the claims, should clear the request context
   context.Clear(so.Request())
   var rawUID interface{}
   if user, ok := claim.(jwt.MapClaims); ok {
   if rawUID, ok = user[setting.JwtUserClaimField]; !ok {
   logger.Error("invalid user claim")
   so.Emit("disconnect", "invalid user claim")
   }
   } else {
   logger.Errorf("invalid jwt claim %s", claim)
   so.Emit("disconnect", "invalid user claim")
   }
   if uid, exist = rawUID.(string); exist {
   // Multi connection for same user will be join to the same room
   so.Join(uid)
   // root for broadcast all user
   so.Join(Hourse)
   c.users.Add(uid, 1)
   logger.Debug("socket connected")
   if setting.DEBUG {
   so.Emit("debug", fmt.Sprintf("Your uid is %s, sid is %s", uid, so.Id()))
   }
   } else {
   so.Emit("disconnect", "invalid user claim")
   }
   so.On("debug", func(data string) {
   log.Debugf("debug data from client %s", data)
   })
   so.On("disconnection", func(data string) {
   logger.Debugf("socket disconnected")
   c.users.Add(uid, -1)
   })
   })
   c.socketio = server
   return nil
   

   }

Finally I fixed the problem.

I use the https://github.com/auth0/go-jwt-middleware to auth with JWT. I also open the KeepContext of gorilla mux router to true for that can get the jwt token of request from the goriila context. When I get the jwt token, will clear the request context (via context.Clear(r)) immediately. So far, all is work correctly. But when the go-jwt-middleware auth failed there is no chance to clear the request context because KeepContext of mux has been to true. This is the root cause.