goroutines have high idle wake up calls

I'm using GoLang to run two websocket clients (one for private and one for public data) simultaneously using goroutines. On the surface, everything seems to work fine. Both clients receive data transmitted from the websocket server. I believe I may have set something up wrong, however, since when I check activity monitor, my program consistently has between 500 - 1500 Idle Wake Ups and is using >200% of my CPU. This doesn't seem normal for something as simple as two websocket clients.

I've put the code in snippets so there's less to read (hopefully that makes it easier to understand), but if you need the entire code, I can post that as well. Here is the code in my main func that runs the ws clients

comms := make(chan os.Signal, 1)
signal.Notify(comms, os.Interrupt, syscall.SIGTERM)
ctx := context.Background()
ctx, cancel := context.WithCancel(ctx)
var wg sync.WaitGroup

wg.Add(1)
go pubSocket.PubListen(ctx, &wg, &activeSubs, testing)
wg.Add(1)
go privSocket.PrivListen(ctx, &wg, &activeSubs, testing)

<- comms
cancel()
wg.Wait()

Here is the code for how the clients run the go routines

func (socket *Socket) PubListen(ctx context.Context, wg *sync.WaitGroup, subManager *ConnStatus, testing bool) {
	defer wg.Done()
	for {
		select {
		case <- ctx.Done():
			log.Println("closing public socket")
			socket.Close()
			return
		default:
			socket.OnTextMessage = func(message string, socket Socket) {
				log.Println(message)
				pubJsonDecoder(message, testing)
				//tradesParser(message);
			}
		}
	}
}

func (socket *Socket) PrivListen(ctx context.Context, wg *sync.WaitGroup, subManager *ConnStatus, testing bool) {
	defer wg.Done()
	for {
		select {
		case <- ctx.Done():
			log.Println("closing private socket")
			socket.Close()
			return
		default:
			socket.OnTextMessage = func(message string, socket Socket) {
				log.Println(message)
			}
		}
	}
}

Any ideas on why the Idle Wake Ups are so high? Should I be using multithreading instead of concurrency? Thanks in advance for any help!

You're wasting CPU here (superfluous loop):

  for {
       // ...
        default:
        // High CPU usage here.
        }
    }

Try something like this:

 func (socket *Socket) PubListen(ctx context.Context, wg *sync.WaitGroup, subManager *ConnStatus, testing bool) {
	defer wg.Done()
	defer socket.Close()

	socket.OnTextMessage = func(message string, socket Socket) {
		log.Println(message)
		pubJsonDecoder(message, testing)
		//tradesParser(message);
	}

	<-ctx.Done()
	log.Println("closing public socket")
}

func (socket *Socket) PrivListen(ctx context.Context, wg *sync.WaitGroup, subManager *ConnStatus, testing bool) {
	defer wg.Done()
	defer socket.Close()

	socket.OnTextMessage = func(message string, socket Socket) {
		log.Println(message)
	}

	<-ctx.Done()
	log.Println("closing private socket")
}

Also this may help:
https://github.com/gorilla/websocket/blob/master/examples/chat/client.go

tl/dr: websockets are hard

It looks like you might have a couple of spinners. You are assigning the handler function for OnTextMessage() in the default case of a for - select statement. The default case always executes if no other cases are ready. Because there is nothing that blocks in the default case, that for loop just spins out of control. Both goroutines spinning like this will likely peg 2 cores. Websockets are network IO and those goroutines are likely to run in parallel. This is why you are seeing 200% utilization.

Take a look at the gorilla/websocket library. I'm not going to say that it is better or worse than any other websocket library, I have a lot of experience with it.

https://github.com/gorilla/websocket

Below is an implementation that I have used many times.
The way it is set up is you register handler functions that are triggered when a certain message is received. Say one of the values in your message was "type" : "start-job", the websocket server will call the handler you assigned to the "start-job" websocket message. It feels like writing endpoints for an http router.

Package serverws

context.go

package serverws
import (
"errors"
"fmt"
"strings"
"sync"
)
// ConnContext is the connection context to track a connected websocket user
type ConnContext struct {
specialKey  string
supportGzip string
UserID      string
mu         sync.Mutex // Websockets are not thread safe, we'll use a mutex to lock writes.
}
// HashKeyAsCtx returns a ConnContext based on the hash provided
func HashKeyAsCtx(hashKey string) (*ConnContext, error) {
values := strings.Split(hashKey, ":")
if len(values) != 3 {
return nil, errors.New("Invalid Key received: " + hashKey)
}
return &ConnContext{values[0], values[1], values[2], sync.Mutex{}}, nil
}
// AsHashKey returns the hash key for a given connection context ConnContext
func (ctx *ConnContext) AsHashKey() string {
return strings.Join([]string{ctx.specialKey, ctx.supportGzip, ctx.UserID}, ":")
}
// String returns a string of the hash of a given connection context ConnContext
func (ctx *ConnContext) String() string {
return fmt.Sprint("specialkey: ", ctx.specialKey, " gzip ", ctx.supportGzip, " auth ", ctx.UserID)
}

wshandler.go

package serverws
import (
"encoding/json"
"errors"
"fmt"
"net/http"
"strings"
"sync"
"time"
"github.com/gorilla/websocket"
"github.com/rs/zerolog/log"
)
var (
receiveFunctionMap = make(map[string]ReceiveObjectFunc)
ctxHashMap         sync.Map
)
// ReceiveObjectFunc is a function signature for a websocket request handler
type ReceiveObjectFunc func(conn *websocket.Conn, ctx *ConnContext, t map[string]interface{})
// WebSocketHandler does what it says, handles WebSockets (makes them easier for us to deal with)
type WebSocketHandler struct {
wsupgrader websocket.Upgrader
}
// WebSocketMessage that is sent over a websocket.   Messages must have a conversation type so the server and the client JS know
// what is being discussed and what signals to raise on the server and the client.
// The "Notification" message instructs the client to display an alert popup.
type WebSocketMessage struct {
MessageType string      `json:"type"`
Message     interface{} `json:"message"`
}
// NewWebSocketHandler sets up a new websocket.
func NewWebSocketHandler() *WebSocketHandler {
wsh := new(WebSocketHandler)
wsh.wsupgrader = websocket.Upgrader{
ReadBufferSize:  4096,
WriteBufferSize: 4096,
}
return wsh
}
// RegisterMessageType sets up an event bus for a message type.   When messages arrive from the client that match messageTypeName,
// the function you wrote to handle that message is then called.
func (wsh *WebSocketHandler) RegisterMessageType(messageTypeName string, f ReceiveObjectFunc) {
receiveFunctionMap[messageTypeName] = f
}
// onMessage triggers when the underlying websocket has received a message.
func (wsh *WebSocketHandler) onMessage(conn *websocket.Conn, ctx *ConnContext, msg []byte, msgType int) {
//  Handling text messages or binary messages. Binary is usually some gzip text.
if msgType == websocket.TextMessage {
wsh.processIncomingTextMsg(conn, ctx, msg)
}
if msgType == websocket.BinaryMessage {
}
}
// onOpen triggers when the underlying websocket has established a connection.
func (wsh *WebSocketHandler) onOpen(conn *websocket.Conn, r *http.Request) (ctx *ConnContext, err error) {
//user, err := gothic.GetFromSession("ID", r)
user := "TestUser"
if err := r.ParseForm(); err != nil {
return nil, errors.New("parameter check error")
}
specialKey := r.FormValue("specialKey")
supportGzip := r.FormValue("support_gzip")
if user != "" && err == nil {
ctx = &ConnContext{specialKey, supportGzip, user, sync.Mutex{}}
} else {
ctx = &ConnContext{specialKey, supportGzip, "", sync.Mutex{}}
}
keyString := ctx.AsHashKey()
if oldConn, ok := ctxHashMap.Load(keyString); ok {
wsh.onClose(oldConn.(*websocket.Conn), ctx)
oldConn.(*websocket.Conn).Close()
}
ctxHashMap.Store(keyString, conn)
return ctx, nil
}
// onClose triggers when the underlying websocket has been closed down
func (wsh *WebSocketHandler) onClose(conn *websocket.Conn, ctx *ConnContext) {
//log.Info().Msg(("client close itself as " + ctx.String()))
wsh.closeConnWithCtx(ctx)
}
// onError triggers when a websocket connection breaks
func (wsh *WebSocketHandler) onError(errMsg string) {
//log.Error().Msg(errMsg)
}
// HandleConn happens when a user connects to us at the listening point.  We ask
// the user to authenticate and then send the required HTTP Upgrade return code.
func (wsh *WebSocketHandler) HandleConn(w http.ResponseWriter, r *http.Request) {
user := ""
if r.URL.Path == "/websocket" {
user = "TestUser" // authenticate however you want
if user == "" {
fmt.Println("UNAUTHENTICATED USER TRIED TO CONNECT TO WEBSOCKET FROM ", r.Header.Get("X-Forwarded-For"))
return
}
}
// don't do this.  You need to check the origin, but this is here as a place holder
wsh.wsupgrader.CheckOrigin = func(r *http.Request) bool {
return true
}
conn, err := wsh.wsupgrader.Upgrade(w, r, nil)
if err != nil {
log.Error().Msg("Failed to set websocket upgrade: " + err.Error())
return
}
defer conn.Close()
ctx, err := wsh.onOpen(conn, r)
if err != nil {
log.Error().Msg("Open connection failed " + err.Error() + r.URL.RawQuery)
if user != "" {
ctx.UserID = user
}
return
}
if user != "" {
ctx.UserID = user
}
conn.SetPingHandler(func(message string) error {
conn.WriteControl(websocket.PongMessage, []byte(message), time.Now().Add(time.Second))
return nil
})
// Message pump for the underlying websocket connection
for {
t, msg, err := conn.ReadMessage()
if err != nil {
// Read errors are when the user closes the tab. Ignore.
wsh.onClose(conn, ctx)
return
}
switch t {
case websocket.TextMessage, websocket.BinaryMessage:
wsh.onMessage(conn, ctx, msg, t)
case websocket.CloseMessage:
wsh.onClose(conn, ctx)
return
case websocket.PingMessage:
case websocket.PongMessage:
}
}
}
func (wsh *WebSocketHandler) closeConnWithCtx(ctx *ConnContext) {
keyString := ctx.AsHashKey()
ctxHashMap.Delete(keyString)
}
func (wsh *WebSocketHandler) processIncomingTextMsg(conn *websocket.Conn, ctx *ConnContext, msg []byte) {
//log.Debug().Msg("CLIENT SAID " + string(msg))
data := WebSocketMessage{}
// try to turn this into data
err := json.Unmarshal(msg, &data)
// And try to get at the data underneath
var raw = make(map[string]interface{})
terr := json.Unmarshal(msg, &raw)
if err == nil {
// What kind of message is this?
if receiveFunctionMap[data.MessageType] != nil {
// We'll try to cast this message and call the handler for it
if terr == nil {
if v, ok := raw["message"].(map[string]interface{}); ok {
receiveFunctionMap[data.MessageType](conn, ctx, v)
} else {
log.Debug().Msg("Nonsense sent over the websocket.")
}
} else {
log.Debug().Msg("Nonsense sent over the websocket.")
}
}
} else {
// Received garbage from the transmitter.
}
}
// SendJSONToSocket sends a specific message to a specific websocket
func (wsh *WebSocketHandler) SendJSONToSocket(socketID string, msg interface{}) {
fields := strings.Split(socketID, ":")
message, _ := json.Marshal(msg)
ctxHashMap.Range(func(key interface{}, value interface{}) bool {
if ctx, err := HashKeyAsCtx(key.(string)); err != nil {
wsh.onError(err.Error())
} else {
if ctx.specialKey == fields[0] {
ctx.mu.Lock()
if value != nil {
err = value.(*websocket.Conn).WriteMessage(websocket.TextMessage, message)
}
ctx.mu.Unlock()
}
if err != nil {
ctx.mu.Lock() // We'll lock here even though we're going to destroy this
wsh.onClose(value.(*websocket.Conn), ctx)
value.(*websocket.Conn).Close()
ctxHashMap.Delete(key) // Remove the websocket immediately
//wsh.onError("WRITE ERR TO USER " + key.(string) + " ERR: " + err.Error())
}
}
return true
})
}

package wsocket

types.go

package wsocket
// Acknowledgement is for ACKing simple messages and sending errors
type Acknowledgement struct {
ResponseID string `json:"responseId"`
Status     string `json:"status"`
IPAddress  string `json:"ipaddress"`
ErrorText  string `json:"errortext"`
}

wsocket.go

package wsocket
import (
"fmt"
server "project/serverws"
"project/utils"
"sync"
"time"
"github.com/gin-gonic/gin"
"github.com/gorilla/websocket"
// "github.com/mitchellh/mapstructure"
"github.com/inconshreveable/log15"
)
var (
WebSocket         *server.WebSocketHandler // So other packages can send out websocket messages
WebSocketLocation string
Log               log15.Logger = log15.New("package", "wsocket"
)
func SetupWebsockets(r *gin.Engine, socket *server.WebSocketHandler, debug_mode bool) {
WebSocket = socket
WebSocketLocation = "example.mydomain.com"
//WebSocketLocation = "example.mydomain.com"
r.GET("/websocket", func(c *gin.Context) {
socket.HandleConn(c.Writer, c.Request)
})
socket.RegisterMessageType("Hello", func(conn *websocket.Conn, ctx *server.ConnContext, data map[string]interface{}) {
response := Acknowledgement{
ResponseID: "Hello",
Status:     fmt.Sprintf("OK/%v", ctx.AuthID),
IPAddress:  conn.RemoteAddr().String(),
}
// mapstructure.Decode(data, &request) -- used if we wanted to read what was fed in
socket.SendJSONToSocket(ctx.AsHashKey(), &response)
})
socket.RegisterMessageType("start-job", func(conn *websocket.Conn, ctx *server.ConnContext, data map[string]interface{}) {
response := Acknowledgement{
ResponseID: "starting_job",
Status:     fmt.Sprintf("%s is being dialed.", data["did"]),
IPAddress:  conn.RemoteAddr().String(),
}
// mapstructure.Decode(data, &request) -- used if we wanted to read what was fed in to a struct.
socket.SendJSONToSocket(ctx.AsHashKey(), &response)
})

This implementation was for a web application. This is a simplified version of the client side in javascript. You can handle many concurrent connections with this implementation and all you do to communicate is define objects/structs that contain a responseID that matches a case in the switch below, it is basically one long switch statement, serialize it and send it to the other side, and the other side will ack. I have some version of this running in several production environments.

websocket.js

$(() => {
function wsMessage(object) {
switch (object.responseId) {
case "Hello": // HELLO! :-)
console.log("Heartbeat received, we're connected.");
break;
case "Notification":
if (object.errortext != "") {
$.notify({
// options
message: '<center><B><i class="fas fa-exclamation-triangle"></i>  ' + object.errortext + '</B></center>',
}, {
// settings
type: 'danger',
offset: 50,
placement: {
align: 'center',
}
});
} else {
$.notify({
// options
message: '<center><B>' + object.status + '</B></center>',
}, {
// settings
type: 'success',
offset: 50,
placement: {
align: 'center',
}
});
}
break;
}
}
$(document).ready(function () {
function heartbeat() {
if (!websocket) return;
if (websocket.readyState !== 1) return;
websocket.send("{\"type\": \"Hello\", \"message\": { \"RequestID\": \"Hello\", \"User\":\"" + /*getCookie("_loginuser")*/"TestUser" + "\"} }");
setTimeout(heartbeat, 24000);
}
//TODO: CHANGE TO WSS once tls is enabled.
function wireUpWebsocket() {
websocket = new WebSocket('wss://' + WEBSOCKET_LOCATION + '/websocket?specialKey=' + WEBSOCKET_KEY + '&support_gzip=0');
websocket.onopen = function (event) {
console.log("Websocket connected.");
heartbeat();
//if it exists
if (typeof (wsReady) !== 'undefined') {
//execute it
wsReady();
}
};
websocket.onerror = function (event) {
console.log("WEBSOCKET ERROR " + event.data);
};
websocket.onmessage = function (event) {
wsMessage(JSON.parse(event.data));
};
websocket.onclose = function () {
// Don't close!
// Replace key
console.log("WEBSOCKET CLOSED");
WEBSOCKET_KEY = Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15);
websocketreconnects++;
if (websocketreconnects > 30) { // Too much, time to bounce
// location.reload(); Don't reload the page anymore, just re-connect.
}
setTimeout(function () { wireUpWebsocket(); }, 3000);
};
}
wireUpWebsocket();
});
});
function getCookie(name) {
var value = "; " + document.cookie;
var parts = value.split("; " + name + "=");
if (parts.length == 2) return parts.pop().split(";").shift();
}
function setCookie(cname, cvalue, exdays) {
var d = new Date();
d.setTime(d.getTime() + (exdays * 24 * 60 * 60 * 1000));
var expires = "expires=" + d.toUTCString();
document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}

Assigning handler functions over and over again in an infinite loop is definitely not going to work.

https://github.com/gorilla/websocket