Emitters sending unnecessarily

[channyeintun]

List emitters = new ArrayList<>();
//...
emitters.forEach(emitter -> {
try {
emitter.send(SseEmitter
.event()
.name(username)
.data(payload));

        } catch (IOException e) {
            deadEmitters.add(emitter);
        }
    });

Above code is not efficient. You should use Map instead of List.

// Should use map
private Map<String, SseEmitter> emitters = new ConcurrentHashMap<>();
// Store in map
emitters.put(username,emitter);
// Get from map
SseEmitter emitter=emitters.get(username);
// you can validate if emitter is null
try {

            emitter.send(SseEmitter
                    .event()
                    .name(username)
                    .data(payload));

        } catch (IOException e) {
             // remove from map
            emitters.remove(username);

}