Send websocket message to user across dynos - spring-boot

Question

I have a spring boot application running on heroku. I make use of websockets for sending messages to and from client and server for a specific user . I use spring boot's SimpMessagingTemplate.convertAndSendToUser to send and receive messages, which works fine for when a user needs get a message back from the server. I use Heroku session affinity which means that even if I scale up the number of sessions the user and websocket still share the same session.
My problem comes when I need a user to send a message to another user. It works fine if both users are sharing the session, but not if the message will not come through.
Is it possible to send a message from one user to another across different sessions using, SimpMessagingTemple? Or would I need to use a message broker, eg Redis.
I was looking into implementing sending a message using StringRedisTemplate but not sure how to send a message to a particular user.
private SimpMessagingTemplate messagingTemplate;
#Autowired
public MessageController(SimpMessagingTemplate messagingTemplate) {
this.messagingTemplate = messagingTemplate;
}
#MessageMapping("/secured/user-in")
public void sendToDevice(Message msg, #AuthenticationPrincipal User principal) throws Exception {
if (msg.getTo() != null) {
String email = msg.getTo();
Message out = new Message();
out.setMsg(msg.getMsg());
out.setFrom(msg.getFrom());
out.setTo(msg.getTo());
out.setSentTime(new Date());
out.setStatus(msg.getStatus());
messagingTemplate.convertAndSendToUser(email, "/secured/topic", out);
}
}
JS
function connect() {
var socket = new SockJS('/secured/user-in');
ST.stompClient = Stomp.over(socket);
var headers = {};
headers[ST.getHeader()] = ST.getToken();
ST.getStompClient().connect(headers, function (frame) {
retries = 1;
console.log('Connected: ' + frame);
ST.getStompClient().subscribe('/user/secured/topic', function (event){
var msg = JSON.parse(event.body);
showMessage(msg.msg);
});
});
}
UPDATE 1
I am guessing I could do something like this, as done here:
SimpMessageHeaderAccessor headerAccessor = SimpMessageHeaderAccessor
.create(SimpMessageType.MESSAGE);
headerAccessor.setSessionId(sessionId);
headerAccessor.setLeaveMutable(true);
messagingTemplate.convertAndSendToUser(sessionId,"/queue/something", payload,
headerAccessor.getMessageHeaders());
But how could I get the session id of another user, I am using Redis to store session info: #EnableRedisHttpSession

Answer 1

I had my terminology a bit mixed up I was trying to send a message to another user on another dyno rather than session.
Ended up using redis sub/pub.
So when a message is receive by the controller it is published to redis, and the redis MessageListenerAdapter envokes the convertAndSendToUser method.
#MessageMapping("/secured/user-in")
public void sendToDevice(Message msg, #AuthenticationPrincipal User principal) throws Exception {
publishMessageToRedis(msg);
}
private void publishMessageToRedis(Message message) throws JsonProcessingException {
ObjectMapper objectMapper = new ObjectMapper();
String messageString = objectMapper.writeValueAsString(message);
stringRedisTemplate.convertAndSend("message", messageString);
}
redis config
#Bean
RedisMessageListenerContainer container( MessageListenerAdapter chatMessageListenerAdapter) throws URISyntaxException {
RedisMessageListenerContainer container = new RedisMessageListenerContainer();
container.setConnectionFactory(connectionFactory());
container.addMessageListener(chatMessageListenerAdapter, new PatternTopic("message"));
return container;
}
#Bean("chatMessageListenerAdapter")
MessageListenerAdapter chatMessageListenerAdapter(RedisReceiver redisReceiver) {
return new MessageListenerAdapter(redisReceiver, "receiveChatMessage");
}
public class RedisReceiver {
private static final Logger LOG = LogManager.getLogger(RedisReceiver.class);
private final WebSocketMessageService webSocketMessageService;
#Autowired
public RedisReceiver(WebSocketMessageService webSocketMessageService) {
this.webSocketMessageService = webSocketMessageService;
}
// Invoked when message is publish to "chat" channel
public void receiveChatMessage(String messageStr) throws IOException {
ObjectMapper objectMapper = new ObjectMapper();
Message message = objectMapper.readValue(messageStr, Message.class);
webSocketMessageService.sendChatMessage(message);
}
}
#Service
public class WebSocketMessageService {
private final SimpMessagingTemplate template;
private static final Logger LOG = LogManager.getLogger(WebSocketMessageService.class);
public WebSocketMessageService(SimpMessagingTemplate template) {
this.template = template;
}
public void sendChatMessage(Message message) {
template.convertAndSendToUser(message.getTo(), "/secured/topic", message);
}
}
Solution was based off this git repository