/**
   * @param cacheCtx Cache context.
   * @return {@code True} if local node can calculate affinity on it's own for this partition map
   *     exchange.
   */
  private boolean canCalculateAffinity(GridCacheContext cacheCtx) {
    AffinityFunction affFunc = cacheCtx.config().getAffinity();

    // Do not request affinity from remote nodes if affinity function is not centralized.
    if (!U.hasAnnotation(affFunc, AffinityCentralizedFunction.class)) return true;

    // If local node did not initiate exchange or local node is the only cache node in grid.
    Collection<ClusterNode> affNodes = CU.affinityNodes(cacheCtx, exchId.topologyVersion());

    return !exchId.nodeId().equals(cctx.localNodeId())
        || (affNodes.size() == 1 && affNodes.contains(cctx.localNode()));
  }
  /** {@inheritDoc} */
  @Override
  public Collection<ClusterNode> nodes(int p, AffinityTopologyVersion topVer) {
    Collection<ClusterNode> affNodes = cctx.affinity().nodes(p, topVer);

    lock.readLock().lock();

    try {
      assert node2part != null && node2part.valid()
          : "Invalid node-to-partitions map [topVer1="
              + topVer
              + ", topVer2="
              + this.topVer
              + ", cache="
              + cctx.name()
              + ", node2part="
              + node2part
              + ']';

      Collection<ClusterNode> nodes = null;

      Collection<UUID> nodeIds = part2node.get(p);

      if (!F.isEmpty(nodeIds)) {
        Collection<UUID> affIds = new HashSet<>(F.viewReadOnly(affNodes, F.node2id()));

        for (UUID nodeId : nodeIds) {
          if (!affIds.contains(nodeId) && hasState(p, nodeId, OWNING, MOVING, RENTING)) {
            ClusterNode n = cctx.discovery().node(nodeId);

            if (n != null
                && (topVer.topologyVersion() < 0 || n.order() <= topVer.topologyVersion())) {
              if (nodes == null) {
                nodes = new ArrayList<>(affNodes.size() + 2);

                nodes.addAll(affNodes);
              }

              nodes.add(n);
            }
          }
        }
      }

      return nodes != null ? nodes : affNodes;
    } finally {
      lock.readLock().unlock();
    }
  }
  /**
   * @param p Partition.
   * @param topVer Topology version ({@code -1} for all nodes).
   * @param state Partition state.
   * @param states Additional partition states.
   * @return List of nodes for the partition.
   */
  private List<ClusterNode> nodes(
      int p,
      AffinityTopologyVersion topVer,
      GridDhtPartitionState state,
      GridDhtPartitionState... states) {
    Collection<UUID> allIds =
        topVer.topologyVersion() > 0 ? F.nodeIds(CU.affinityNodes(cctx, topVer)) : null;

    lock.readLock().lock();

    try {
      assert node2part != null && node2part.valid()
          : "Invalid node-to-partitions map [topVer="
              + topVer
              + ", allIds="
              + allIds
              + ", node2part="
              + node2part
              + ", cache="
              + cctx.name()
              + ']';

      Collection<UUID> nodeIds = part2node.get(p);

      // Node IDs can be null if both, primary and backup, nodes disappear.
      int size = nodeIds == null ? 0 : nodeIds.size();

      if (size == 0) return Collections.emptyList();

      List<ClusterNode> nodes = new ArrayList<>(size);

      for (UUID id : nodeIds) {
        if (topVer.topologyVersion() > 0 && !allIds.contains(id)) continue;

        if (hasState(p, id, state, states)) {
          ClusterNode n = cctx.discovery().node(id);

          if (n != null && (topVer.topologyVersion() < 0 || n.order() <= topVer.topologyVersion()))
            nodes.add(n);
        }
      }

      return nodes;
    } finally {
      lock.readLock().unlock();
    }
  }