/** Checks consistency after all operations. */
  private void consistencyCheck() {
    if (CONSISTENCY_CHECK) {
      assert lock.writeLock().isHeldByCurrentThread();

      if (node2part == null) return;

      for (Map.Entry<UUID, GridDhtPartitionMap> e : node2part.entrySet()) {
        for (Integer p : e.getValue().keySet()) {
          Set<UUID> nodeIds = part2node.get(p);

          assert nodeIds != null
              : "Failed consistency check [part=" + p + ", nodeId=" + e.getKey() + ']';
          assert nodeIds.contains(e.getKey())
              : "Failed consistency check [part="
                  + p
                  + ", nodeId="
                  + e.getKey()
                  + ", nodeIds="
                  + nodeIds
                  + ']';
        }
      }

      for (Map.Entry<Integer, Set<UUID>> e : part2node.entrySet()) {
        for (UUID nodeId : e.getValue()) {
          GridDhtPartitionMap map = node2part.get(nodeId);

          assert map != null
              : "Failed consistency check [part=" + e.getKey() + ", nodeId=" + nodeId + ']';
          assert map.containsKey(e.getKey())
              : "Failed consistency check [part=" + e.getKey() + ", nodeId=" + nodeId + ']';
        }
      }
    }
  }
  /** {@inheritDoc} */
  @Nullable
  @Override
  public GridDhtPartitionMap partitions(UUID nodeId) {
    lock.readLock().lock();

    try {
      return node2part.get(nodeId);
    } finally {
      lock.readLock().unlock();
    }
  }
  /** {@inheritDoc} */
  @Override
  public GridDhtPartitionState partitionState(UUID nodeId, int part) {
    lock.readLock().lock();

    try {
      GridDhtPartitionMap partMap = node2part.get(nodeId);

      if (partMap != null) {
        GridDhtPartitionState state = partMap.get(part);

        return state == null ? EVICTED : state;
      }

      return EVICTED;
    } finally {
      lock.readLock().unlock();
    }
  }
  /**
   * @param p Partition.
   * @param nodeId Node ID.
   * @param match State to match.
   * @param matches Additional states.
   * @return Filter for owners of this partition.
   */
  private boolean hasState(
      final int p,
      @Nullable UUID nodeId,
      final GridDhtPartitionState match,
      final GridDhtPartitionState... matches) {
    if (nodeId == null) return false;

    GridDhtPartitionMap parts = node2part.get(nodeId);

    // Set can be null if node has been removed.
    if (parts != null) {
      GridDhtPartitionState state = parts.get(p);

      if (state == match) return true;

      if (matches != null && matches.length > 0)
        for (GridDhtPartitionState s : matches) if (state == s) return true;
    }

    return false;
  }
  /** {@inheritDoc} */
  @SuppressWarnings({"MismatchedQueryAndUpdateOfCollection"})
  @Nullable
  @Override
  public GridDhtPartitionMap update(
      @Nullable GridDhtPartitionExchangeId exchId, GridDhtPartitionFullMap partMap) {
    if (log.isDebugEnabled())
      log.debug(
          "Updating full partition map [exchId=" + exchId + ", parts=" + fullMapString() + ']');

    assert partMap != null;

    lock.writeLock().lock();

    try {
      if (stopping) return null;

      if (exchId != null && lastExchangeId != null && lastExchangeId.compareTo(exchId) >= 0) {
        if (log.isDebugEnabled())
          log.debug(
              "Stale exchange id for full partition map update (will ignore) [lastExchId="
                  + lastExchangeId
                  + ", exchId="
                  + exchId
                  + ']');

        return null;
      }

      if (node2part != null && node2part.compareTo(partMap) >= 0) {
        if (log.isDebugEnabled())
          log.debug(
              "Stale partition map for full partition map update (will ignore) [lastExchId="
                  + lastExchangeId
                  + ", exchId="
                  + exchId
                  + ", curMap="
                  + node2part
                  + ", newMap="
                  + partMap
                  + ']');

        return null;
      }

      long updateSeq = this.updateSeq.incrementAndGet();

      if (exchId != null) lastExchangeId = exchId;

      if (node2part != null) {
        for (GridDhtPartitionMap part : node2part.values()) {
          GridDhtPartitionMap newPart = partMap.get(part.nodeId());

          // If for some nodes current partition has a newer map,
          // then we keep the newer value.
          if (newPart != null && newPart.updateSequence() < part.updateSequence()) {
            if (log.isDebugEnabled())
              log.debug(
                  "Overriding partition map in full update map [exchId="
                      + exchId
                      + ", curPart="
                      + mapString(part)
                      + ", newPart="
                      + mapString(newPart)
                      + ']');

            partMap.put(part.nodeId(), part);
          }
        }

        for (Iterator<UUID> it = partMap.keySet().iterator(); it.hasNext(); ) {
          UUID nodeId = it.next();

          if (!cctx.discovery().alive(nodeId)) {
            if (log.isDebugEnabled())
              log.debug(
                  "Removing left node from full map update [nodeId="
                      + nodeId
                      + ", partMap="
                      + partMap
                      + ']');

            it.remove();
          }
        }
      }

      node2part = partMap;

      Map<Integer, Set<UUID>> p2n = new HashMap<>(cctx.affinity().partitions(), 1.0f);

      for (Map.Entry<UUID, GridDhtPartitionMap> e : partMap.entrySet()) {
        for (Integer p : e.getValue().keySet()) {
          Set<UUID> ids = p2n.get(p);

          if (ids == null)
            // Initialize HashSet to size 3 in anticipation that there won't be
            // more than 3 nodes per partitions.
            p2n.put(p, ids = U.newHashSet(3));

          ids.add(e.getKey());
        }
      }

      part2node = p2n;

      boolean changed = checkEvictions(updateSeq);

      consistencyCheck();

      if (log.isDebugEnabled()) log.debug("Partition map after full update: " + fullMapString());

      return changed ? localPartitionMap() : null;
    } finally {
      lock.writeLock().unlock();
    }
  }
  /**
   * Updates value for single partition.
   *
   * @param p Partition.
   * @param nodeId Node ID.
   * @param state State.
   * @param updateSeq Update sequence.
   */
  @SuppressWarnings({"MismatchedQueryAndUpdateOfCollection"})
  private void updateLocal(int p, UUID nodeId, GridDhtPartitionState state, long updateSeq) {
    assert lock.isWriteLockedByCurrentThread();
    assert nodeId.equals(cctx.nodeId());

    // In case if node joins, get topology at the time of joining node.
    ClusterNode oldest = CU.oldestAliveCacheServerNode(cctx.shared(), topVer);

    assert oldest != null;

    // If this node became the oldest node.
    if (oldest.id().equals(cctx.nodeId())) {
      long seq = node2part.updateSequence();

      if (seq != updateSeq) {
        if (seq > updateSeq) {
          if (this.updateSeq.get() < seq) {
            // Update global counter if necessary.
            boolean b = this.updateSeq.compareAndSet(this.updateSeq.get(), seq + 1);

            assert b
                : "Invalid update sequence [updateSeq="
                    + updateSeq
                    + ", seq="
                    + seq
                    + ", curUpdateSeq="
                    + this.updateSeq.get()
                    + ", node2part="
                    + node2part.toFullString()
                    + ']';

            updateSeq = seq + 1;
          } else updateSeq = seq;
        }

        node2part.updateSequence(updateSeq);
      }
    }

    GridDhtPartitionMap map = node2part.get(nodeId);

    if (map == null)
      node2part.put(
          nodeId,
          map =
              new GridDhtPartitionMap(
                  nodeId,
                  updateSeq,
                  Collections.<Integer, GridDhtPartitionState>emptyMap(),
                  false));

    map.updateSequence(updateSeq);

    map.put(p, state);

    Set<UUID> ids = part2node.get(p);

    if (ids == null) part2node.put(p, ids = U.newHashSet(3));

    ids.add(nodeId);
  }
  /** {@inheritDoc} */
  @SuppressWarnings({"MismatchedQueryAndUpdateOfCollection"})
  @Nullable
  @Override
  public GridDhtPartitionMap update(
      @Nullable GridDhtPartitionExchangeId exchId, GridDhtPartitionMap parts) {
    if (log.isDebugEnabled())
      log.debug(
          "Updating single partition map [exchId=" + exchId + ", parts=" + mapString(parts) + ']');

    if (!cctx.discovery().alive(parts.nodeId())) {
      if (log.isDebugEnabled())
        log.debug(
            "Received partition update for non-existing node (will ignore) [exchId="
                + exchId
                + ", parts="
                + parts
                + ']');

      return null;
    }

    lock.writeLock().lock();

    try {
      if (stopping) return null;

      if (lastExchangeId != null && exchId != null && lastExchangeId.compareTo(exchId) > 0) {
        if (log.isDebugEnabled())
          log.debug(
              "Stale exchange id for single partition map update (will ignore) [lastExchId="
                  + lastExchangeId
                  + ", exchId="
                  + exchId
                  + ']');

        return null;
      }

      if (exchId != null) lastExchangeId = exchId;

      if (node2part == null)
        // Create invalid partition map.
        node2part = new GridDhtPartitionFullMap();

      GridDhtPartitionMap cur = node2part.get(parts.nodeId());

      if (cur != null && cur.updateSequence() >= parts.updateSequence()) {
        if (log.isDebugEnabled())
          log.debug(
              "Stale update sequence for single partition map update (will ignore) [exchId="
                  + exchId
                  + ", curSeq="
                  + cur.updateSequence()
                  + ", newSeq="
                  + parts.updateSequence()
                  + ']');

        return null;
      }

      long updateSeq = this.updateSeq.incrementAndGet();

      node2part = new GridDhtPartitionFullMap(node2part, updateSeq);

      boolean changed = false;

      if (cur == null || !cur.equals(parts)) changed = true;

      node2part.put(parts.nodeId(), parts);

      part2node = new HashMap<>(part2node);

      // Add new mappings.
      for (Integer p : parts.keySet()) {
        Set<UUID> ids = part2node.get(p);

        if (ids == null)
          // Initialize HashSet to size 3 in anticipation that there won't be
          // more than 3 nodes per partition.
          part2node.put(p, ids = U.newHashSet(3));

        changed |= ids.add(parts.nodeId());
      }

      // Remove obsolete mappings.
      if (cur != null) {
        for (Integer p : F.view(cur.keySet(), F0.notIn(parts.keySet()))) {
          Set<UUID> ids = part2node.get(p);

          if (ids != null) changed |= ids.remove(parts.nodeId());
        }
      }

      changed |= checkEvictions(updateSeq);

      consistencyCheck();

      if (log.isDebugEnabled()) log.debug("Partition map after single update: " + fullMapString());

      return changed ? localPartitionMap() : null;
    } finally {
      lock.writeLock().unlock();
    }
  }