func wsWriter(ws *websocket.Conn) {
graphIn := broker.Get().Subscribe()
pingTicker := time.NewTicker(pingPeriod)
defer func() {
pingTicker.Stop()
broker.Get().Unsubscribe(graphIn)
ws.Close()
}()
// write the current graph state first, before entering loop
graphToSock(ws, latestGraph)
var g system.CoreGraph
for {
select {
case <-pingTicker.C:
// ensure client connection is healthy
ws.SetWriteDeadline(time.Now().Add(writeWait))
if err := ws.WriteMessage(websocket.PingMessage, []byte{}); err != nil {
return
}
case g = <-graphIn:
graphToSock(ws, g)
}
}
}
func graphToSock(ws *websocket.Conn, g system.CoreGraph) {
j, err := graphToJSON(g)
if err != nil {
logrus.WithFields(logrus.Fields{
"system": "webapp",
"err": err,
}).Error("Error while marshaling graph into JSON for transmission over websocket")
}
if j != nil {
ws.SetWriteDeadline(time.Now().Add(writeWait))
if err := ws.WriteMessage(websocket.TextMessage, j); err != nil {
logrus.WithFields(logrus.Fields{
"system": "webapp",
"err": err,
}).Error("Error while writing graph data to websocket")
return
}
}
}
func writer(ws *websocket.Conn, lastMod time.Time) {
lastError := ""
pingTicker := time.NewTicker(pingPeriod)
fileTicker := time.NewTicker(filePeriod)
defer func() {
pingTicker.Stop()
fileTicker.Stop()
ws.Close()
}()
for {
select {
case <-fileTicker.C:
var p []byte
var err error
p, lastMod, err = readFileIfModified(lastMod)
if err != nil {
if s := err.Error(); s != lastError {
lastError = s
p = []byte(lastError)
}
} else {
lastError = ""
}
if p != nil {
ws.SetWriteDeadline(time.Now().Add(writeWait))
if err := ws.WriteMessage(websocket.TextMessage, p); err != nil {
return
}
}
case <-pingTicker.C:
ws.SetWriteDeadline(time.Now().Add(writeWait))
if err := ws.WriteMessage(websocket.PingMessage, []byte{}); err != nil {
return
}
}
}
}