avoid concurrent write to websocket when sending keep-alive messages

fixes #213

this probably only happen in very busy clusters :)

backend/actions.go

@@ -9,6 +9,7 @@ type Action struct {
 }
 
 const (
+	keepAlive           = "INTERNAL_KEEP_ALIVE"
 	errorNotification   = "ERROR_NOTIFICATION"
 	successNotification = "SUCCESS_NOTIFICATION"
 )

backend/nomad_connection.go

@@ -299,7 +299,7 @@ func (c *NomadConnection) keepAlive() {
 			return
 		case <-ticker.C:
 			logger.Debugf("Sending keep-alive packet")
-			c.socket.WriteMessage(websocket.PingMessage, []byte("keepalive"))
+			c.send <- &Action{Type: keepAlive, Payload: "hello-world", Index: 0}
 		}
 	}
 }