【发布时间】：2019-04-24 06:40:43
【问题描述】：
我有一个通过 API 和 websocket 进行通信的应用程序。 如果在数据库中发生更改，websocket 用于将更新的用户数据发布到客户端 - 这非常有效，除了在某些情况下 websocket 没有接收任何数据的情况。几秒钟后，websocket 又开始工作了。
服务器日志（首先websocket不工作，重新开始工作）
msg="向 Websocket 写入数据失败：websocket: 关闭发送"
msg="向客户端发送 Ping 消息"
msg="无法将 ping 消息写入 Websocket: websocket: close sent"
msg="向客户端发送 Ping 消息"
msg="向客户端发送 Ping 消息"
msg="向客户端发送 Ping 消息"
msg="向客户端发送 Ping 消息"
客户端代码：
<html>
<body>
<p id="data"></p>
</body>
<script>
var ws = new WebSocket("wss://example.com/ws");
function unloadPage() {
toggleLoader();
ws.onclose = function () {};
ws.close();
}
ws.onopen = function () {
ws.send('Ping');
};
ws.onerror = function (error) {
console.log('WebSocket Error ' + error);
var d = document.getElementById("data");
d.innerHTML += "<tr><td>Failed to connect to Server.</td></tr>"
};
ws.onmessage = function (e) {
console.log(e);
var data = e.data;
var d = document.getElementById("data");
var parsedjson = JSON.parse(data);
d.innerHTML = "";
for (var i = 0; i < parsedjson.length; i++) {
d.innerHTML += parsedjson;
}
};
ws.onclose = function () {
console.log("Websocket has been closed");
};
window.addEventListener("beforeunload", unloadPage);
</script>
</html>
Go 代码（通过 gorilla mux 路由）：
var (
upgrader = websocket.Upgrader{
ReadBufferSize: 1024,
WriteBufferSize: 1024,
CheckOrigin: func(r *http.Request) bool { return true },
}
pingPeriod = (pongPeriod * 9) / 10
pongPeriod = 60 * time.Second
writeWait = 10 * time.Second
)
func PingResponse(ws *websocket.Conn) {
conf := storage.GetConfig()
defer ws.Close()
ws.SetReadLimit(512)
ws.SetReadDeadline(time.Now().Add(pongPeriod))
ws.SetPongHandler(func(string) error { ws.SetReadDeadline(time.Now().Add(pongPeriod)); return nil })
for {
_, _, err := ws.ReadMessage()
if err != nil {
if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway) {
conf.Log.Debugf("Websocket Ping Read Failed: %v", err)
}
return
} else {
conf.Log.Debugf("Received message from Websocket client")
}
}
}
func ServeAllUsersWebsocket(datachan chan *[]storage.UserResponse) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
conf := storage.GetConfig()
ws, err := upgrader.Upgrade(w, r, nil)
if err != nil {
conf.Log.Debugf("Failed to upgrade data to Websocket: %v", err)
return
}
go allUserWebsocketWriter(ws, datachan)
go PingResponse(ws)
})
}
func allUserWebsocketWriter(ws *websocket.Conn, datachan chan *[]storage.UserResponse) {
conf := storage.GetConfig()
pingticker := time.NewTicker(pingPeriod)
defer func() {
pingticker.Stop()
ws.Close()
}()
userresponse, err := conf.Database.GetAllUsers()
if err != nil {
conf.Log.Errorf("Failed to query users from database: %v", err)
return
}
ws.SetWriteDeadline(time.Now().Add(writeWait))
err = ws.WriteJSON(&userresponse)
if err != nil {
conf.Log.Debugf("Failed to write initial user response: %v", err)
return
}
for {
select {
case data := <-datachan:
ws.SetWriteDeadline(time.Now().Add(writeWait))
err := ws.WriteJSON(&data)
if err != nil {
conf.Log.Debugf("Failed to write data to Websocket: %v", err)
return
}
case <-pingticker.C:
ws.SetWriteDeadline(time.Now().Add(writeWait))
conf.Log.Debugf("Sending Ping Message to Client")
if err := ws.WriteMessage(websocket.PingMessage, []byte{}); err != nil {
conf.Log.Debugf("Failed to write ping message to Websocket: %v", err)
return
}
}
}
}
基本上，当更新时，我们会将当前数据发布到新的 Websocket 连接 - 这总是有效的。之后，如果数据库发生变化，它会将更新的用户列表发布到通道中——然后 websocket 应该将其发布到更新列表的客户端。我们还发送 ping 消息 - 失败（如上面的日志所示）。客户端本身不会记录任何错误或关闭 websocket。
【问题讨论】：