logger("%s: Send failure for node:%s resources:%d size:%s%s: %v",
				v3.GetShortType(w.TypeUrl), con.proxy.ID, len(res), util.ByteCount(configSize), info, err)
		}
		return err
	}

	switch {
	case !req.Full:
		if deltaLog.DebugEnabled() {
			deltaLog.Debugf("%s: %s%s for node:%s resources:%d size:%s%s",
				v3.GetShortType(w.TypeUrl), ptype, req.PushReason(), con.proxy.ID, len(res), util.ByteCount(configSize), info)

			if req.TypeUrl == model.HealthInfoType && !initialRequestsSent.Load() {
				// only send healthcheck probe after LDS request has been sent
				continue
			}
			log.WithLabels(
				"type", model.GetShortType(req.TypeUrl),
				"sub", len(req.ResourceNamesSubscribe),
				"unsub", len(req.ResourceNamesUnsubscribe),
				"nonce", req.ResponseNonce,
				"initial", len(req.InitialResourceVersions),
			).Debugf("delta request")

// using WatchedResource for previous state and discovery request for the current state.
func ShouldRespond(w Watcher, id string, request *discovery.DiscoveryRequest) (bool, ResourceDelta) {
	stype := model.GetShortType(request.TypeUrl)

	// If there is an error in request that means previous response is erroneous.
	// We do not have to respond in that case. In this case request's version info

)

var deltaLog = log.RegisterScope("deltaadsc", "delta adsc debugging")

type resourceKey struct {
	Name    string
	TypeURL string
}

func (k resourceKey) shortName() string {
	return v3.GetShortType(k.TypeURL) + "/" + k.Name
}

type keySet = sets.Set[resourceKey]

// resourceNode represents a resource state in the dynamic tree structure of the service mesh.

// protection. Original code avoided the mutexes by doing both 'push' and 'process requests' in same thread.
func (s *DiscoveryServer) processRequest(req *discovery.DiscoveryRequest, con *Connection) error {
	stype := v3.GetShortType(req.TypeUrl)
	log.Debugf("ADS:%s: REQ %s resources:%d nonce:%s version:%s ", stype,
		con.ID(), len(req.ResourceNames), req.ResponseNonce, req.VersionInfo)
	if req.TypeUrl == v3.HealthInfoType {

		select {
		case resp := <-con.responsesChan:
			// TODO: separate upstream response handling from requests sending, which are both time costly
			proxyLog.WithLabels(
				"id", con.conID,
				"type", model.GetShortType(resp.TypeUrl),
				"resources", len(resp.Resources),
			).Debugf("upstream response")
			metrics.XdsProxyResponses.Increment()
			if h, f := p.handlers[resp.TypeUrl]; f {
				if len(resp.Resources) == 0 {