Expose kubernetes logs to browser through websocket - web

Question

I am trying to use sidecar mode in kubernetes to create a logs sidecar to expose specific container logs. And I am using kubernetes client to fetch logs from kubernetes api and send it out by websocket. The code shows below:
func serveWs(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Access-Control-Allow-Origin", "*")
conn, err := upgrader.Upgrade(w, r, nil)
if err != nil {
if _, ok := err.(websocket.HandshakeError); !ok {
log.Println(err)
}
return
}
defer conn.Close()
logsClient, err := InitKubeLogsClient(config.InCluster)
if err != nil {
log.Fatalln(err)
}
stream, err := logsClient.GetLogs(config.Namespace, config.PodName, config.ContainerName)
if err != nil {
log.Fatalln(err)
}
defer stream.Close()
reader := bufio.NewReader(stream)
for {
line, err := reader.ReadString('\n')
if err != nil {
log.Fatalln(err)
}
conn.WriteMessage(websocket.TextMessage, []byte(line))
}
}
I am using https://github.com/gorilla/websocket as the websocket lib. And on the browser
Is this the best way to do what I want? Is there some better way to just expose the logs api from k8s to websocket?

Answer 1

Put my final code here, thanks for the tips from #Peter:
func serveWs(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Access-Control-Allow-Origin", "*")
conn, err := upgrader.Upgrade(w, r, nil)
if err != nil {
if _, ok := err.(websocket.HandshakeError); !ok {
log.Println(err)
}
return
}
log.Println("create new connection")
defer func() {
conn.Close()
log.Println("connection close")
}()
logsClient, err := InitKubeLogsClient(config.InCluster)
if err != nil {
log.Println(err)
return
}
stream, err := logsClient.GetLogs(config.Namespace, config.PodName, config.ContainerName)
if err != nil {
log.Println(err)
return
}
defer stream.Close()
reader := bufio.NewReaderSize(stream, 16)
lastLine := ""
for {
data, isPrefix, err := reader.ReadLine()
if err != nil {
log.Println(err)
return
}
lines := strings.Split(string(data), "\r")
length := len(lines)
if len(lastLine) > 0 {
lines[0] = lastLine + lines[0]
lastLine = ""
}
if isPrefix {
lastLine = lines[length-1]
lines = lines[:(length - 1)]
}
for _, line := range lines {
if err := conn.WriteMessage(websocket.TextMessage, []byte(line)); err != nil {
log.Println(err)
return
}
}
}
}