/** {@inheritDoc} */
  @Override
  public Map<GridRichNode, Collection<K>> mapKeysToNodes(Collection<? extends K> keys) {
    Map<GridRichNode, Collection<K>> map = new HashMap<GridRichNode, Collection<K>>();

    for (K key : keys) {
      Collection<GridRichNode> nodes = ctx.allNodes(key);

      for (GridRichNode node : nodes) {
        Collection<K> keyCol = map.get(node);

        if (keyCol == null) map.put(node, keyCol = new LinkedList<K>());

        keyCol.add(key);
      }
    }

    return map;
  }
  /** {@inheritDoc} */
  @Override
  public void unlockAll(
      Collection<? extends K> keys, GridPredicate<? super GridCacheEntry<K, V>>[] filter) {
    if (keys.isEmpty()) return;

    try {
      GridCacheVersion ver = null;

      Collection<GridRichNode> affNodes = null;

      int keyCnt = -1;

      Map<GridRichNode, GridNearUnlockRequest<K, V>> map = null;

      Collection<K> locKeys = new LinkedList<K>();

      GridCacheVersion obsoleteVer = ctx.versions().next();

      for (K key : keys) {
        while (true) {
          GridDistributedCacheEntry<K, V> entry = peekExx(key);

          if (entry == null || !ctx.isAll(entry.wrap(false), filter)) break; // While.

          try {
            GridCacheMvccCandidate<K> cand =
                entry.candidate(ctx.nodeId(), Thread.currentThread().getId());

            if (cand != null) {
              ver = cand.version();

              if (affNodes == null) {
                affNodes = CU.allNodes(ctx, cand.topologyVersion());

                keyCnt = (int) Math.ceil((double) keys.size() / affNodes.size());

                map = new HashMap<GridRichNode, GridNearUnlockRequest<K, V>>(affNodes.size());
              }

              // Send request to remove from remote nodes.
              GridRichNode primary = CU.primary0(ctx.affinity(key, affNodes));

              GridNearUnlockRequest<K, V> req = map.get(primary);

              if (req == null) {
                map.put(primary, req = new GridNearUnlockRequest<K, V>(keyCnt));

                req.version(ver);
              }

              // Remove candidate from local node first.
              GridCacheMvccCandidate<K> rmv = entry.removeLock();

              if (rmv != null) {
                if (!rmv.reentry()) {
                  if (ver != null && !ver.equals(rmv.version()))
                    throw new GridException(
                        "Failed to unlock (if keys were locked separately, "
                            + "then they need to be unlocked separately): "
                            + keys);

                  if (!primary.isLocal()) {
                    assert req != null;

                    req.addKey(entry.key(), entry.getOrMarshalKeyBytes(), ctx);
                  } else locKeys.add(key);

                  if (log.isDebugEnabled()) log.debug("Removed lock (will distribute): " + rmv);
                } else if (log.isDebugEnabled())
                  log.debug(
                      "Current thread still owns lock (or there are no other nodes)"
                          + " [lock="
                          + rmv
                          + ", curThreadId="
                          + Thread.currentThread().getId()
                          + ']');
              }

              // Try to evict near entry if it's dht-mapped locally.
              evictNearEntry(entry, obsoleteVer);
            }

            break;
          } catch (GridCacheEntryRemovedException ignore) {
            if (log.isDebugEnabled())
              log.debug("Attempted to unlock removed entry (will retry): " + entry);
          }
        }
      }

      if (ver == null) return;

      for (Map.Entry<GridRichNode, GridNearUnlockRequest<K, V>> mapping : map.entrySet()) {
        GridRichNode n = mapping.getKey();

        GridDistributedUnlockRequest<K, V> req = mapping.getValue();

        if (n.isLocal()) dht.removeLocks(ctx.nodeId(), req.version(), locKeys, true);
        else if (!req.keyBytes().isEmpty())
          // We don't wait for reply to this message.
          ctx.io().send(n, req);
      }
    } catch (GridException ex) {
      U.error(log, "Failed to unlock the lock for keys: " + keys, ex);
    }
  }