下面left()方法, 很奇怪, 在遍历中移除竟然没报错, 猜测是 线程池submit吃掉了异常, 具体没深入看.

public abstract class AbstractWsHandler implements WsHandler {
    protected Set<String> rooms;
    public void left(String room) {
        if (!Strings.isBlank(room)) {
            rooms.remove(room);
            room = prefix + room;
            log.debugf("session(id=%s) left room(name=%s)", session.getId(), room);
            roomProvider.left(room, session.getId());
        }
    }

    public void depose() {
        for (String room : rooms) {
            left(room);
        }
    }
}

建议改成

for (Object room : mRooms.toArray()) {
        left(String.valueOf(room));
 }