英文:
I cannot escape a for loop with a ticker
问题
我有一个API，它会每秒钟通过web-socket扫描司机的位置并发送。问题是，当客户端断开连接时，循环无法退出。它似乎会一直运行下去。我正在使用Gin和nhooyr websocket库。
var GetDriverLocations = func(c *gin.Context) {
wsoptions := websocket.AcceptOptions{InsecureSkipVerify: true}
wsconn, err := websocket.Accept(c.Writer, c.Request, &wsoptions)
if err != nil {
return
}
defer wsconn.Close(websocket.StatusInternalError, "the sky is falling")
driverLocation := &models.DriverLocation{}
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
for {
select {
case <-ticker.C:
case <-c.Request.Context().Done():
fmt.Println("done") //这句话永远不会被打印出来
return
}
coords, err := driverLocation.GetDrivers()
if err != nil {
break
}
err = wsjson.Write(c.Request.Context(), wsconn, &coords)
if websocket.CloseStatus(err) == websocket.StatusNormalClosure {
break
}
if err != nil {
break
}
}
fmt.Println("conn ended") //这句话永远不会被打印出来
}
我还尝试了这个循环，但也有同样的问题：
for range ticker.C{
coords, err := driverLocation.GetDrivers()
if err != nil {
break
}
err = wsjson.Write(c.Request.Context(), wsconn, &coords)
if websocket.CloseStatus(err) == websocket.StatusNormalClosure {
break
}
if err != nil {
break
}
}
英文:
I have this API that scans for drivers' locations and send them via web-socket every 1 second. The issue is that the loop cannot be escaped when client disconnects. It seems it is alive for ever. I am using Gin with nhooyr websocket library.
var GetDriverLocations = func(c *gin.Context) {
wsoptions := websocket.AcceptOptions{InsecureSkipVerify: true}
wsconn, err := websocket.Accept(c.Writer, c.Request, &wsoptions)
if err != nil {
return
}
defer wsconn.Close(websocket.StatusInternalError, "the sky is falling")
driverLocation := &models.DriverLocation{}
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
for {
select {
case <-ticker.C:
case <-c.Request.Context().Done():
fmt.Println("done") //this never gets printed
return
}
coords, err := driverLocation.GetDrivers()
if err != nil {
break
}
err = wsjson.Write(c.Request.Context(), wsconn, &coords)
if websocket.CloseStatus(err) == websocket.StatusNormalClosure {
break
}
if err != nil {
break
}
}
fmt.Println("conn ended") //this never gets printed
}
I also tried this loop but also has the same issue:
for range ticker.C{
coords, err := driverLocation.GetDrivers()
if err != nil {
break
}
err = wsjson.Write(c.Request.Context(), wsconn, &coords)
if websocket.CloseStatus(err) == websocket.StatusNormalClosure {
break
}
if err != nil {
break
}
}
答案1
得分: 0
因为网络连接被nhooyr websocket库从net/http服务器劫持，所以直到处理程序返回之前，上下文c.Request.Context()不会被取消。
调用CloseRead以获取在连接关闭时取消的上下文。在循环中使用该上下文。
var GetDriverLocations = func(c *gin.Context) {
wsoptions := websocket.AcceptOptions{InsecureSkipVerify: true}
wsconn, err := websocket.Accept(c.Writer, c.Request, &wsoptions)
if err != nil {
return
}
defer wsconn.Close(websocket.StatusInternalError, "")
ctx := wsconn.CloseRead(c.Request.Context())
driverLocation := &models.DriverLocation{}
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
for {
select {
case <-ticker.C:
case <-ctx.Done():
return
}
coords, err := driverLocation.GetDrivers()
if err != nil {
break
}
err = wsjson.Write(c.Request.Context(), wsconn, &coords)
if err != nil {
break
}
}
}
英文:
Because the network connection is hijacked from the net/http server by the nhooyr websocket library, the context c.Request.Context() is not canceled until handler returns.
Call CloseRead to get a context that's canceled when the connection is closed. Use that context in the loop.
var GetDriverLocations = func(c *gin.Context) {
wsoptions := websocket.AcceptOptions{InsecureSkipVerify: true}
wsconn, err := websocket.Accept(c.Writer, c.Request, &wsoptions)
if err != nil {
return
}
defer wsconn.Close(websocket.StatusInternalError, "")
ctx := wsconn.CloseRead(c.Request.Context())
driverLocation := &models.DriverLocation{}
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
for {
select {
case <-ticker.C:
case <-ctx.Done():
return
}
coords, err := driverLocation.GetDrivers()
if err != nil {
break
}
err = wsjson.Write(c.Request.Context(), wsconn, &coords)
if err != nil {
break
}
}
}
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