public List<DiscoveryUpstreamDataSubscriber> getDiscoveryUpstreamDataSubscribers() {
        return discoveryUpstreamDataSubscribers;
    }
get discovery upstream data subscriber.

@return discovery upstream data subscriber
shenyu-sync-data-center/shenyu-sync-data-websocket/src/main/java/org/apache/shenyu/plugin/sync/data/websocket/WebsocketSyncDataService.java