Golang WebSocket保存多文件时连接异常断开问题排查

问题描述 #

尝试通过WebSocket在Golang服务器上保存多个音频文件，但每次创建单个文件后，WebSocket连接就会断开，报错websocket: close 1001 (going away)。移除文件保存的代码块后，循环可以正常运行。请排查客户端导致连接断开的原因。

服务端代码 #

conn, err := upgrader.Upgrade(c.Writer, c.Request, nil)
if err != nil {
    fmt.Println("Error upgrading to WebSocket:", err)
    return
}
defer conn.Close()
for i := 0; ; i++ {
    questionaire:= questionaires[i].msg //a couple of questions to be sent to client
    if i == 0 {
        // send initial message to frontend
        sendServerMessageToClient(conn, questionaire)
    } else {
        messageType, msg, err := conn.ReadMessage()
        if err != nil || err == io.EOF {
            fmt.Println(err) // this line here logs the websocket error
            break
        }
        response = ""
        if messageType == websocket.BinaryMessage {

            // if this blocks of code here is removed, it works, otherwise restarts the websocket connection
            fileName := fmt.Sprintf("answer%d.wav", i)
            file, err := os.Create(fileName)
            if err != nil {
                fmt.Println(err)
            }
              
            _, err = file.Write(msg)
            if err != nil {
                fmt.Println(err)
            }
            // til here
           // handle the saved file and call to speech to text api 
            
           response = "yes" //assumed the response is "yes"
        }
        switch response {
        case "yes":
            if i < len(questionaires) {
                sendServerMessageToClient(conn, questionaire)
            } else {
                sendServerMessageToClient(conn, "end")
                return
            }
        case "no":
            sendServerMessage(conn, "Exiting")
            return
        default:
            i--
        }
    }
}

客户端代码 #

....
    <div id="statusLabel">Status: Waiting for server...</div><br><br>
    <audio controls id="audioPlayer"></audio><br><br>
    <button onclick="startRecording()">Start Recording</button>
    <button onclick="stopRecording()">Stop Recording</button>

    <script>
        const statusLabel = document.getElementById('statusLabel');
        const audioPlayer = document.getElementById('audioPlayer');
        let mediaRecorder;
        let audioChunks = [];
        let ws;

        function startRecording() {
            navigator.mediaDevices.getUserMedia({ audio: true })
                .then((stream) => {
                    audioChunks = [];
                    statusLabel.textContent = "Status: Recording...";
                    mediaRecorder = new MediaRecorder(stream);
                    mediaRecorder.ondataavailable = (event) => {
                        if (event.data.size > 0) {
                            audioChunks.push(event.data);
                            ws.send(event.data);
                        }
                    };
                    mediaRecorder.onstop = () => {
                        const audioBlob = new Blob(audioChunks, { type: 'audio/wav' });
                        const audioUrl = URL.createObjectURL(audioBlob);
                        audioPlayer.src = audioUrl;
                    };
                    mediaRecorder.start();
                })
                .catch((error) => console.error('Error accessing microphone:', error));
        }

        function stopRecording() {
            statusLabel.textContent = "Stopped recording";
            ws.send("stop"); // Notify the server to stop recording
            mediaRecorder.stop();
        }

        // Establish WebSocket connection
        ws = new WebSocket("ws://golang-server.com/ws");

        ws.onmessage = (event) => {
            statusLabel.textContent = `${event.data}`;
        };

        ws.onclose = (event) => {
            statusLabel.textContent = "Connection closed";
        };
    </script>
 ...

问题排查与修复方案 #

客户端侧核心问题 #

1. 分片发送音频数据导致服务器阻塞超时
   MediaRecorder.start()默认会每隔几百毫秒触发ondataavailable事件，客户端每次收到数据就调用ws.send(event.data)发送小二进制块。服务器在处理文件写入时（磁盘IO操作）会阻塞ReadMessage()循环，无法及时响应客户端的后续消息，客户端因长时间未收到服务器反馈，主动触发连接断开（1001错误）。

2. 发送的"stop"文本消息未被服务器处理
   点击停止时客户端发送字符串"stop"（文本类型），但服务器仅处理BinaryMessage类型，此时response为空进入default分支，i--导致循环卡住，服务器无法继续发送消息，客户端长期无响应后主动断开。

修复建议 #

客户端修改

• 合并音频后一次性发送：移除ondataavailable中的ws.send(event.data)，仅在onstop时发送完整的音频Blob，减少频繁通信对服务器的压力：

mediaRecorder.ondataavailable = (event) => {
    if (event.data.size > 0) {
        audioChunks.push(event.data);
        // 移除此处的ws.send(event.data)
    }
};
mediaRecorder.onstop = () => {
    const audioBlob = new Blob(audioChunks, { type: 'audio/wav' });
    const audioUrl = URL.createObjectURL(audioBlob);
    audioPlayer.src = audioUrl;
    // 一次性发送完整音频
    ws.send(audioBlob);
};

• 调整停止逻辑：如果需要保留"stop"通知，需确保服务器能处理文本消息，或者改为在发送完完整音频后由服务器判断流程结束。

服务端配套修改

• 关闭文件句柄：文件写入后必须关闭，避免句柄泄漏和磁盘缓存阻塞：

fileName := fmt.Sprintf("answer%d.wav", i)
file, err := os.Create(fileName)
if err != nil {
    fmt.Println(err)
    continue
}
defer file.Close() // 新增：确保文件关闭
_, err = file.Write(msg)
if err != nil {
    fmt.Println(err)
}

• 处理文本消息：添加文本消息分支，处理客户端的"stop"指令：

if messageType == websocket.BinaryMessage {
    // 原文件保存逻辑
} else if messageType == websocket.TextMessage {
    msgStr := string(msg)
    if msgStr == "stop" {
        sendServerMessage(conn, "Exiting")
        return
    }
}

• 添加心跳机制：服务器定期发送Ping帧，客户端回复Pong，避免因长时间无通信被客户端判定为连接失效。

内容的提问来源于stack exchange，提问作者San