/**
   * @param cctx Cache context.
   * @param prj Projection (optional).
   * @return Collection of data nodes in provided projection (if any).
   */
  private static Collection<ClusterNode> nodes(
      final GridCacheContext<?, ?> cctx,
      @Nullable final ClusterGroup prj,
      @Nullable final Integer part) {
    assert cctx != null;

    final AffinityTopologyVersion topVer = cctx.affinity().affinityTopologyVersion();

    Collection<ClusterNode> affNodes = CU.affinityNodes(cctx);

    if (prj == null && part == null) return affNodes;

    final Set<ClusterNode> owners =
        part == null
            ? Collections.<ClusterNode>emptySet()
            : new HashSet<>(cctx.topology().owners(part, topVer));

    return F.view(
        affNodes,
        new P1<ClusterNode>() {
          @Override
          public boolean apply(ClusterNode n) {

            return cctx.discovery().cacheAffinityNode(n, cctx.name())
                && (prj == null || prj.node(n.id()) != null)
                && (part == null || owners.contains(n));
          }
        });
  }
  /**
   * @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()));
  }
  /**
   * @param cacheCtx Cache context.
   * @throws IgniteCheckedException If failed.
   */
  private void initTopology(GridCacheContext cacheCtx) throws IgniteCheckedException {
    if (stopping(cacheCtx.cacheId())) return;

    if (canCalculateAffinity(cacheCtx)) {
      if (log.isDebugEnabled())
        log.debug(
            "Will recalculate affinity [locNodeId="
                + cctx.localNodeId()
                + ", exchId="
                + exchId
                + ']');

      cacheCtx.affinity().calculateAffinity(exchId.topologyVersion(), discoEvt);
    } else {
      if (log.isDebugEnabled())
        log.debug(
            "Will request affinity from remote node [locNodeId="
                + cctx.localNodeId()
                + ", exchId="
                + exchId
                + ']');

      // Fetch affinity assignment from remote node.
      GridDhtAssignmentFetchFuture fetchFut =
          new GridDhtAssignmentFetchFuture(
              cacheCtx,
              exchId.topologyVersion(),
              CU.affinityNodes(cacheCtx, exchId.topologyVersion()));

      fetchFut.init();

      List<List<ClusterNode>> affAssignment = fetchFut.get();

      if (log.isDebugEnabled())
        log.debug(
            "Fetched affinity from remote node, initializing affinity assignment [locNodeId="
                + cctx.localNodeId()
                + ", topVer="
                + exchId.topologyVersion()
                + ']');

      if (affAssignment == null) {
        affAssignment = new ArrayList<>(cacheCtx.affinity().partitions());

        List<ClusterNode> empty = Collections.emptyList();

        for (int i = 0; i < cacheCtx.affinity().partitions(); i++) affAssignment.add(empty);
      }

      cacheCtx.affinity().initializeAffinity(exchId.topologyVersion(), affAssignment);
    }
  }
  /**
   * @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();
    }
  }