（转到）在ws循环中比较不断变化的变量

Question

Working on a loop that receives messages and processes them accordingly, basically a websocket echo-er with keep-alives and authentication, and I've been stuck in the keep-alive part for a little while now.

The concept is simple, when the server starts I create a goroutine with a ticker, and I initialize a uint64 pointer, each time that ticker ticks (every 2 seconds), I increment the pointer with atomic.AddUint64(clockTicks, 1), then for each websocket connection goroutine, I check the variable every tick with a compare and atomic.LoadUint64(clockTicks), and I send a ping/pong message.

Edit: Seems like something is blocking the for loop until a message is received, result:

i := atomic.LoadUint64(clockTicks)
    if i != cur {
        cur = i
        if act != true {
            fmt.Println("Quit Nao U filthy bot.")
            return
        } else {
            fmt.Println("Keep Going.")
            act = false
        }
    }

In this snippet, i := atomic.LoadUint64(clockTicks) & all the if block only runs when i message is sent (Prints "Keep Going." on msg), which is not what I want, I want the snippet to run every for iteration, and "Keep Going." & "Quit nao ..." to trigger everytime clockTicks is incremented

Here's the important code parts, I'm using Go and Gorilla's Websockets library:

func Clock() {
clockTicks = new(uint64)
*clockTicks = 0
clock := time.NewTicker(authIntervals).C
for {
    <-clock
    atomic.AddUint64(clockTicks, 1)
}
}

var wsu = websocket.Upgrader{
ReadBufferSize:  1024,
WriteBufferSize: 1024,
CheckOrigin:     OriginHandler,
}

func serveWS(w http.ResponseWriter, r *http.Request) {
if r.Method != "GET" {
    http.Error(w, "Method not allowed", 405)
    return
}

ws, err := wsu.Upgrade(w, r, nil)
if err != nil {
    fmt.Println(err)
    return
}

defer ws.Close()
cur := atomic.LoadUint64(clockTicks)
var act, val = true, false
for {
    i := atomic.LoadUint64(clockTicks)
    if i != cur { /* Only triggers when I receive a msg */
        cur = i
        if act != true {
            fmt.Println("Quit Nao U filthy bot.")
            return
        } else {
            fmt.Println("Keep Going.")
            act = false
        }
    }

    mtype, p, err := ws.ReadMessage()
    if err != nil {
        return
    }

    ...

}

Edit 2: Someone in IRC suggested that maybe ws.ReadMessage is blocking, but I'm not really sure (He says ioutil.ReadAll used in ws.ReadMessage implementation is blocking it, and he's pretty sure about it)

Answer 1

The websocket read methods call the network connection Read method to get data from the network. Because the network connection Read method blocks, the webscocket methods also block.

To send pings, use a ticker in the write loop as in the Gorilla chat example or run a separate goroutine for pings as in Gorilla command example.