Reactive Spring Data Mongodb Query is returning old data when it should not

Question

I am trying to only fetch newly created messages from a reactive Mongodb repository using Spring Data.

The client is fetching the messages via SSE. I am using an "after"-query, which should only return messages which were sent after "LocalDateTime.now()".

Unfortunately the SSE is pushing out old messages which are older than "now", too. I have no clue why it returns those old messages.

My controller method:

    @GetMapping(value = "/receiving-sse", produces = "text/event-stream")
    public Flux<Message> streamEvents() {
        Mono<String> username = getUsernameFromAuth();

        Flux<Message> message = findOrCreateUser(username)
                .flatMapMany(user -> messageRepository
                        .findAllBySenderIdOrReceiverIdAndSentAtAfter(user.getId(), user.getId(), LocalDateTime.now()));

        Flux<Message> heartBeat = Flux.interval(Duration.ofSeconds(30)).map(sequence -> {
            Message heartBeatMessage = new Message();
            heartBeatMessage.setHeartbeat(true);
            return heartBeatMessage;
        });

        return Flux.merge(message, heartBeat);
    }

My repository:

public interface MessageRepository extends ReactiveMongoRepository<Message, String> {

    Flux<Message> findAllByReceiverId(String receiverId);

    @Tailable
    Flux<Message> findAllBySenderIdOrReceiverIdAndSentAtAfter(String senderId, String receiverId, LocalDateTime sentAt);

    Flux<Message> findAllBySenderId(String senderId);

    Flux<Message> findAllByIdIn(Collection<String> ids);

}

And my document:

@Data
@Document
public class Message {

    private String id;

    private LocalDateTime sentAt;

    private String message;

    private boolean heartbeat;

    @DBRef
    private User sender;

    @DBRef
    private User receiver;
}

Any hints on why the repo is fetching messages that have a "sentAt" older than "LocalDateTime.now()" is much appreciated.

Answer 1

Problem is in LocalDateTime.now() . LocalDateTime creates a time during initialization of a Flux<Message> message variable.

You need to replace it with construction like Mono.defer() . It will create LocalDateTime in every subscribe.

More you can read here