Sending message from Kafka Streams to a WebSocket with Quarkus

Question

So I'm not sure how to do this. I've done this using Quarkus and the MicroProfile Reactive Messaging framework and the javax.websocket library stuff but I'm not sure how I can port this to using Kafka Streams. With MP Reactive Messaging I can just have an @Outgoing annotation on a channel in one of my other classes and then with my WebSocket service I can inject from that channel like so.

@ServerEndpoint("/validatedmessages")
@ApplicationScoped
public class WebSocket {

@Inject @Channel("post-final-check") Flowable<CustomMessage> finalizedMessages;
//private Jsonb jsonb;
ObjectMapper obj = new ObjectMapper(); 

private static final Logger LOGGER = Logger.getLogger(WebSocket.class);

private List<Session> sessions = new CopyOnWriteArrayList<>();
private Disposable subscription;

@OnOpen
public void onOpen(Session session) {
    sessions.add(session);
}

@OnClose
public void onClose(Session session) {
    sessions.remove(session);
}

@PostConstruct
public void subscribe() {
    subscription = finalizedMessages.subscribe(message -> sessions.forEach(session -> {
        try {
            write(session, message);
        } catch (JsonProcessingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }));
}

@PreDestroy
public void cleanup() throws Exception {
    subscription.dispose();
    //jsonb.close();
}

Is it possible to do this with Kafka Streams?

did you ever found a solution to this? – dondragon2 Jul 18 '22 at 20:02 — dondragon2, Jul 18 '22 at 20:02

score 0 · Answer 1 · answered Jul 17 '20 at 08:51

Where do you store your output of Kafka Streams ? In topics or KTable ?

If it is the first, then you can inject a Publisher or use @Incoming(topic). Otherwise you need to use InteractiveQueries, see here for an example:

https://quarkus.io/guides/kafka-streams#interactive-queries

Sending message from Kafka Streams to a WebSocket with Quarkus

1 Answers1