std::unordered_map<Output, BackproppedGradients, OutputHash, OutputEq>
      backprops_;

  // pending[i] is count-down counter for i-th node's expected
  // backprops.  When pending[i] becomes zero, we collected all
  // backprop gradients for all outputs of the ith-node.
  std::vector<int> pending_;

  // `ready` keeps track of nodes that have been completely

                        PendingOperation pending = pendings.remove(finish.id);
                        assert pending != null;

                        List<BuildOperationRecord> children = childrens.remove(finish.id);
                        assert children != null;

                        SerializedOperationStart start = pending.start;

// pending value in the cache.
func (cache *EndpointSliceCache) esDataChanged(serviceKey types.NamespacedName, sliceKey string, esData *endpointSliceData) bool {
	if _, ok := cache.trackerByServiceMap[serviceKey]; ok {
		appliedData, appliedOk := cache.trackerByServiceMap[serviceKey].applied[sliceKey]
		pendingData, pendingOk := cache.trackerByServiceMap[serviceKey].pending[sliceKey]

// Every time envoy makes a fresh connection to the agent, we reestablish a new connection to the upstream xds
// This ensures that a new connection between istiod and agent doesn't end up consuming pending messages from envoy
// as the new connection may not go to the same istiod. Vice versa case also applies.
func (p *XdsProxy) DeltaAggregatedResources(downstream DeltaDiscoveryStream) error {

      },
      {
         "datasource": {
            "type": "datasource",
            "uid": "-- Mixed --"
         },
         "description": "Count of active and pending proxies managed by each instance.\nPending is expected to converge to zero.\n",
         "fieldConfig": {
            "defaults": {
               "custom": {
                  "fillOpacity": 10,
                  "gradientMode": "hue",

    NodeVisitState state = visitedNodes.get(node);
    if (state == NodeVisitState.COMPLETE) {
      return false;
    }
    if (state == NodeVisitState.PENDING) {
      return true;
    }

    visitedNodes.put(node, NodeVisitState.PENDING);
    for (N nextNode : graph.successors(node)) {
      if (canTraverseWithoutReusingEdge(graph, nextNode, previousNode)

    NodeVisitState state = visitedNodes.get(node);
    if (state == NodeVisitState.COMPLETE) {
      return false;
    }
    if (state == NodeVisitState.PENDING) {
      return true;
    }

    visitedNodes.put(node, NodeVisitState.PENDING);
    for (N nextNode : graph.successors(node)) {
      if (canTraverseWithoutReusingEdge(graph, nextNode, previousNode)

public interface PendingDependenciesVisitor {

    enum PendingState {
        PENDING(true),
        NOT_PENDING(false),
        NOT_PENDING_ACTIVATING(false);

        private final boolean pending;

        PendingState(boolean pending) {
            this.pending = pending;
        }

        boolean isPending() {
            return this.pending;
        }
    }

            while (!finished && pending == null) {
                try {
                    lock.wait();
                } catch (InterruptedException e) {
                    throw UncheckedException.throwAsUncheckedException(e);
                }
            }
            if (pending != null) {
                UserInput result = pending;
                pending = null;
                return result;
            }

    @Override
    public boolean isEmpty() {
        return values.isEmpty() && pending.isEmpty();
    }

    @Override
    public boolean constantTimeIsEmpty() {
        return values.isEmpty() && pending.isEmpty();
    }

    @Override
    public int size() {
        int pendingSize = 0;
        for (Collectors.TypedCollector<T> collector : pending) {
            pendingSize += collector.size();
        }