fix: adds WebSocket ping to interactive terminal (#14191)

server/application/terminal.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"io"
 	"net/http"
+	"time"
 
 	"github.com/argoproj/gitops-engine/pkg/utils/kube"
 	log "github.com/sirupsen/logrus"
@@ -228,6 +229,10 @@ func (s *terminalHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 	defer session.Done()
 
+	// send pings across the WebSocket channel at regular intervals to keep it alive through
+	// load balancers which may close an idle connection after some period of time
+	go session.StartKeepalives(time.Second * 5)
+
 	if isValidShell(s.allowedShells, shell) {
 		cmd := []string{shell}
 		err = startProcess(kubeClientset, config, namespace, podName, container, cmd, session)

server/application/websocket.go

@@ -51,6 +51,23 @@ func (t *terminalSession) Done() {
 	close(t.doneChan)
 }
 
+func (t *terminalSession) StartKeepalives(dur time.Duration) {
+	ticker := time.NewTicker(dur)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			err := t.Ping()
+			if err != nil {
+				log.Errorf("ping error: %v", err)
+				return
+			}
+		case <-t.doneChan:
+			return
+		}
+	}
+}
+
 // Next called in a loop from remotecommand as long as the process is running
 func (t *terminalSession) Next() *remotecommand.TerminalSize {
 	select {
@@ -86,6 +103,17 @@ func (t *terminalSession) Read(p []byte) (int, error) {
 	}
 }
 
+// Ping called periodically to ensure connection stays alive through load balancers
+func (t *terminalSession) Ping() error {
+	t.writeLock.Lock()
+	err := t.wsConn.WriteMessage(websocket.PingMessage, []byte("ping"))
+	t.writeLock.Unlock()
+	if err != nil {
+		log.Errorf("ping message err: %v", err)
+	}
+	return err
+}
+
 // Write called from remotecommand whenever there is any output
 func (t *terminalSession) Write(p []byte) (int, error) {
 	msg, err := json.Marshal(TerminalMessage{