go - 如何将一些事件更新从 http 处理程序发送到 WebSocket 处理程序

Question

我是 Go 语言的新手，正在尝试了解 channel 。为了理清我的理解，我观看了视频教程，阅读了一些书籍，但在使用 Go 编写的 Web 应用程序中进行实际编码和 channel 使用时，我仍然感到困惑。

我想要做的是拥有 2 个 URL:

1. 显示或获取值的通常的正常 GET 或 POST URL 和处理它。在后端做一些处理，我希望处理要在 websocket 更新中发送的输出URL，因此不需要窗口刷新/重新加载。
2. 基于 Gorilla 包的 websockets URL。

以下是迄今为止我尝试过的测试代码，它仍然是我试图制定解决方案的困惑代码的精简版本:

//file main.go
package main

import (
    "io"
    "net/http"
    "fmt"
    "math/rand"
    "log"
    "time"
    "github.com/gorilla/websocket"
)


func logging(f http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        log.Println(r.URL.Path)
        if r.URL.Path == `/ws` {
            log.Println("WebSocket is accessed from ws://localhost:8080/ws")
        }
        f(w, r)
    }
}

type hotcat int

func (c hotcat) ServeHTTP(res http.ResponseWriter, req *http.Request) {
    io.WriteString(res, "cat cat cat")

    //Some code here who's output I want to pass to websockets url ws://localhost:8080/ws
    n := timeConsumingWork(4)
    fmt.Println("Random Number Print from cat: ", n)
    //Example the value of n I need to pass to ws://localhost:8080/ws, how can I do it?

    // Some other example test code just giving some random output from hotcat http handler
    // Would like to pass it's output to ws://localhost:8080/ws to print in websocckets output in browser
    go func(){
        out := make(chan string)
        go func(){
            for i := 0; ; i++ {
                out <- `foo said something`
                time.Sleep(time.Duration(rand.Intn(2e3)) * time.Millisecond)
            }
            //out <- `foo said something`
        }()
        printer(out)
    }()
}

var upgrader = websocket.Upgrader{
    ReadBufferSize:  1024,
    WriteBufferSize: 1024,
    CheckOrigin: func(r *http.Request) bool {
        return true
    },
}

// Execute this in browser console to initiate websococket connection and to send ws.send() commands etc.
/*
var ws = new WebSocket("ws://localhost:8080/ws")
ws.addEventListener("message", function(e) {console.log(e);});
ws.onmessage = function (event) {
    console.log(event.data);
}

ws.send("foo")
ws.send(JSON.stringify({username: "Sat"}))

ws.readyState
ws.CLOSED
ws.OPEN
ws.close()
*/
func ws(w http.ResponseWriter, r *http.Request) {
    socket, err := upgrader.Upgrade(w, r, nil)
    if err != nil {
        fmt.Println(err)
        return
    }
    for {
        msgType, msg, err := socket.ReadMessage()
        if err != nil {
            fmt.Println(err)
            return
        }
        fmt.Println(string(msg))
        if err = socket.WriteMessage(msgType, msg); err != nil {
            fmt.Println(err)
        }
    }
}

func main() {
    var c hotcat

    http.Handle("/cat", c)
    http.HandleFunc("/ws", logging(ws))

    http.ListenAndServe(":8080", nil)
}


func timeConsumingWork(n int) int {
    time.Sleep(time.Microsecond * time.Duration(rand.Intn(500)))
    return n + rand.Intn(1000)
}


func printer(in <-chan string) {
    //log.Println(<-in)
    go func() {
        for {
            log.Println(<-in)
        }
    }()
}

# command shell output
$ go run main.go 

Random Number Print from cat:  891
2019/03/11 14:15:32 foo said something
2019/03/11 14:15:33 /ws
2019/03/11 14:15:33 WebSocket is accessed from ws://localhost:8080/ws
foo
2019/03/11 14:15:34 foo said something
2019/03/11 14:15:34 foo said something
2019/03/11 14:15:34 foo said something
2019/03/11 14:15:36 foo said something
2019/03/11 14:15:36 foo said something
^Csignal: interrupt
$ 

我想显示随机输出字符串“2019/03/11 14:15:34 foo said something”，就像浏览器中 websocket 输出中的输出一样。

我真的很感激一些指导或帮助。

我认为这个问题的代码、终端输出和浏览器截图中的注释应该清楚我正在尝试做什么，但如果这个问题仍然不清楚，请告诉我，我会尝试扩展它更多。

感谢和问候，

桑德

更新 1:

我阅读并尝试了聊天应用程序的 Mat Ryer 示例:https://github.com/matryer/goblueprints/tree/master/chapter1/chat

这是可能的代码副本:https://github.com/satindergrewal/golang-practice/tree/master/chat-examples/mychat02

从示例中我了解到，如果我有一个 Web 套接字句柄，我可以将消息从该 WebSocket http 句柄传送到其他连接的 Web 客户端。但我仍然很困惑如何将消息从非 websocket http 句柄发送到 websocket 句柄路由/地址。

我知道我不能只将此代码用于 / 的 ServeHTTP:

// ServeHTTP handles the HTTP request.
func (t *templateHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    t.once.Do(func() {
        t.templ = template.Must(template.ParseFiles(filepath.Join("templates", t.filename)))
    })
    fmt.Println(r.Host)
    t.templ.Execute(w, r)
    var room *room
    socket, _ := upgrader.Upgrade(w, r, nil)
    client := &client{
        socket: socket,
        send:   make(chan []byte, messageBufferSize),
        room:   room,
    }
    room.join <- client
    go func() {
        for i := 0; i < 10; i++ {
            time.Sleep(time.Duration(rand.Intn(8e3)) * time.Millisecond)
            client.socket.WriteMessage(websocket.TextMessage, []byte("Hello from / ServeHTTP Handle"))
            //fmt.Println("Sending automatic hello from root ServeHTTP handle to web page!")
        }
    }()
}

它已经给我以下错误:

localhost:8080
2019/03/25 11:19:18 http: superfluous response.WriteHeader call from github.com/gorilla/websocket.(*Upgrader).returnError (server.go:81)
2019/03/25 11:19:18 http: panic serving [::1]:52691: runtime error: invalid memory address or nil pointer dereference
goroutine 39 [running]:
net/http.(*conn).serve.func1(0xc00013e140)
        /usr/local/Cellar/go/1.12.1/libexec/src/net/http/server.go:1769 +0x139
panic(0x13a3e00, 0x172dc20)
        /usr/local/Cellar/go/1.12.1/libexec/src/runtime/panic.go:522 +0x1b5
main.(*templateHandler).ServeHTTP(0xc00008ef60, 0x14954a0, 0xc0001dc380, 0xc000214200)
        /Users/satinder/go/src/golang-practice/chat-examples/mychat02/main.go:40 +0x209
net/http.(*ServeMux).ServeHTTP(0x173cfa0, 0x14954a0, 0xc0001dc380, 0xc000214200)
        /usr/local/Cellar/go/1.12.1/libexec/src/net/http/server.go:2375 +0x1d6
net/http.serverHandler.ServeHTTP(0xc000130000, 0x14954a0, 0xc0001dc380, 0xc000214200)
        /usr/local/Cellar/go/1.12.1/libexec/src/net/http/server.go:2774 +0xa8
net/http.(*conn).serve(0xc00013e140, 0x1495ba0, 0xc0000a0380)
        /usr/local/Cellar/go/1.12.1/libexec/src/net/http/server.go:1878 +0x851
created by net/http.(*Server).Serve
        /usr/local/Cellar/go/1.12.1/libexec/src/net/http/server.go:2884 +0x2f4

更新 2: 在重新阅读评论的第一个回复后，尝试了不同的方法。

// ServeHTTP handles the HTTP request.
func (t *templateHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    t.once.Do(func() {
        t.templ = template.Must(template.ParseFiles(filepath.Join("templates", t.filename)))
    })
    fmt.Println(r.Host)
    t.templ.Execute(w, r)

    room := newRoom()
    go func() {
        for i := 0; i < 10; i++ {
            time.Sleep(time.Duration(rand.Intn(8e3)) * time.Millisecond)
            room.forward <- []byte("Hello from / ServeHTTP Handle")
            //client.socket.WriteMessage(websocket.TextMessage, []byte("Hello from / ServeHTTP Handle"))
            fmt.Println("Sending automatic hello from root ServeHTTP handle to web page!")
        }
    }()
}

现在它没有给出错误，但我没有看到控制台显示添加的第二个客户端，我期望通过命令行添加 /。

GoldenBook:mychat02 satinder$ go build -o chat 
GoldenBook:mychat02 satinder$ ./chat 
2019/03/25 11:37:49 Starting web server on :8080
localhost:8080
New client joined
^C

再次尝试使用以前和新的代码组合，结果如下:

// ServeHTTP handles the HTTP request.
func (t *templateHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    t.once.Do(func() {
        t.templ = template.Must(template.ParseFiles(filepath.Join("templates", t.filename)))
    })
    fmt.Println(r.Host)
    t.templ.Execute(w, r)

    room := newRoom()
    socket, _ := upgrader.Upgrade(w, r, nil)
    client := &client{
        socket: socket,
        send:   make(chan []byte, messageBufferSize),
        room:   room,
    }
    room.join <- client
    go func() {
        for i := 0; i < 10; i++ {
            time.Sleep(time.Duration(rand.Intn(8e3)) * time.Millisecond)
            room.forward <- []byte("Hello from / ServeHTTP Handle")
            //client.socket.WriteMessage(websocket.TextMessage, []byte("Hello from / ServeHTTP Handle"))
            //fmt.Println("Sending automatic hello from root ServeHTTP handle to web page!")
        }
    }()
}

GoldenBook:mychat02 satinder$ go build -o chat 
GoldenBook:mychat02 satinder$ ./chat 
2019/03/25 11:40:44 Starting web server on :8080
localhost:8080
2019/03/25 11:40:50 http: superfluous response.WriteHeader call from github.com/gorilla/websocket.(*Upgrader).returnError (server.go:81)
^C

还是一头雾水……

有人可以给我一个解决方案吗？非常感谢您的帮助。

提前致谢。

桑德

Answer 1

我想我已经解决了。至少它正在做我想象中的代码来做我想做的事情，即使它可能不是正确的做事方式。正确的做事方式或做这件事的有效方式，我想你们中的许多人可能会纠正我并帮助我这样做，我希望如此，所以如果您认为它是错误的或低效的，请发表评论并纠正我。

我是这样解决的:

我查看了 gorilla 的 websocket 示例的 echo 示例 ( https://github.com/gorilla/websocket/blob/master/examples/echo/client.go )，并从 clients.go 文件中获取了一些基本代码，它是 make作为客户端连接到 websocket。

我的最终目标是将事件更新从另一个 http 句柄发送到 websocket，因此我在控制台输出中模拟了一些字符串的打印日志示例。

这是我在 Mat Ryer 聊天示例代码的 main.go 文件中所做的更改:

// ServeHTTP handles the HTTP request.
func (t *templateHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    t.once.Do(func() {
        t.templ = template.Must(template.ParseFiles(filepath.Join("templates", t.filename)))
    })
    fmt.Println(r.Host)
    t.templ.Execute(w, r)

    // Creating the URL scheme to use with websocket Dialer
    // to connnect to ws://localhost:8080/room
    u := url.URL{Scheme: "ws", Host: "localhost:8080", Path: "/room"}
    log.Printf("connecting to %s", u.String())

    // Initiate the websocket connection from the go code **as a client** to connect to the chat room
    c, _, err := websocket.DefaultDialer.Dial(u.String(), nil)
    if err != nil {
        log.Fatal("dial:", err)
    }

    go func() {
        for i := 0; i < 10; i++ {
            time.Sleep(time.Duration(rand.Intn(8e3)) * time.Millisecond)
            // Just printing the log of the same message in command line. Might better to ignore it.
            // log.Println("Sending automatic hello from root ServeHTTP handle to web page!")

            // Write the Message as Text message to the web socket connection
            // which will show up in the chat box
            err := c.WriteMessage(websocket.TextMessage, []byte("Sending automatic hello from root ServeHTTP handle to web page!"))
            if err != nil {
                log.Println("write:", err)
                return
            }
        }
    }()
}

构建二进制文件后运行此代码会在控制台中打印以下示例输出:

GoldenBook:mychat02 satinder$ ./chat 
2019/03/31 03:44:27 Starting web server on :8080
localhost:8080
2019/03/31 03:44:31 connecting to ws://localhost:8080/room
New client joined
New client joined
2019/03/31 03:44:33 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
2019/03/31 03:44:36 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
2019/03/31 03:44:43 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
2019/03/31 03:44:45 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
2019/03/31 03:44:45 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
Message received: HELLO
-- sent to client
-- sent to client
2019/03/31 03:44:48 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
2019/03/31 03:44:48 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
2019/03/31 03:44:49 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
2019/03/31 03:44:52 Sending automatic hello from root ServeHTTP handle to web page!
Message received: Sending automatic hello from root ServeHTTP handle to web page!
-- sent to client
-- sent to client
^C

以下是在 http://localhost:8080/ 的网页中显示的输出

这是完整的代码更新: https://github.com/satindergrewal/golang-practice/tree/master/chat-examples/mychat02

因为这是我想为我的实际应用程序解决的示例代码，它是一个基于 WebTTY 的应用程序，我将能够使用此代码将 WebTTY session 结束事件更新从其他一些 http 句柄发送到 websocket位。

我仍然可以使用在线围棋大师的一些帮助。

我需要在某个地方添加靠近此拨号器的 channel 吗？我想我知道，但如果有人可以修复其中的任何错误或预期的低效率，我将不胜感激。

非常感谢 @cerise-limón 到目前为止对我的帮助。 :-)