Suporte a transações Spring Data MongoDB 4.0

ClientSession session = client.startSession(options);                   

template.withSession(session)
    .execute(action -> {
        session.startTransaction();                                     
        try {

            Step step = // ...;
            action.insert(step);
            process(step);
            action.update(Step.class).apply(Update.set("state", // ...
            session.commitTransaction();                                
        } catch (RuntimeException e) {
            session.abortTransaction();                                 
        }
    }, ClientSession::close)                                            
    .subscribe();