/**
   * @param nodeId Node ID.
   * @param req Request.
   */
  @SuppressWarnings({"RedundantTypeArguments"})
  public void clearLocks(UUID nodeId, GridDhtUnlockRequest<K, V> req) {
    assert nodeId != null;

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

    List<K> keys = req.nearKeys();

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

          try {
            if (entry != null) {
              entry.doneRemote(
                  req.version(), req.version(), req.committedVersions(), req.rolledbackVersions());

              // Note that we don't reorder completed versions here,
              // as there is no point to reorder relative to the version
              // we are about to remove.
              if (entry.removeLock(req.version())) {
                if (log.isDebugEnabled())
                  log.debug("Removed lock [lockId=" + req.version() + ", key=" + key + ']');

                // Try to evict near entry dht-mapped locally.
                evictNearEntry(entry, obsoleteVer);
              } else {
                if (log.isDebugEnabled())
                  log.debug(
                      "Received unlock request for unknown candidate "
                          + "(added to cancelled locks set): "
                          + req);
              }
            } else if (log.isDebugEnabled())
              log.debug("Received unlock request for entry that could not be found: " + req);

            break;
          } catch (GridCacheEntryRemovedException ignored) {
            if (log.isDebugEnabled())
              log.debug(
                  "Received remove lock request for removed entry (will retry) [entry="
                      + entry
                      + ", req="
                      + req
                      + ']');
          }
        }
      }
    }
  }
  /**
   * Removes locks regardless of whether they are owned or not for given version and keys.
   *
   * @param ver Lock version.
   * @param keys Keys.
   */
  @SuppressWarnings({"unchecked"})
  public void removeLocks(GridCacheVersion ver, Collection<? extends K> keys) {
    if (keys.isEmpty()) return;

    try {
      Collection<GridRichNode> affNodes = null;

      int keyCnt = -1;

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

      for (K key : keys) {
        // Send request to remove from remote nodes.
        GridNearUnlockRequest<K, V> req = null;

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

          try {
            if (entry != null) {
              GridCacheMvccCandidate<K> cand = entry.candidate(ver);

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

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

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

                GridRichNode primary = CU.primary0(ctx.affinity(key, affNodes));

                if (!primary.isLocal()) {
                  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.
                if (entry.removeLock(cand.version())) {
                  if (primary.isLocal()) {
                    dht.removeLocks(primary.id(), ver, F.asList(key), true);

                    assert req == null;

                    continue;
                  }

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

            break;
          } catch (GridCacheEntryRemovedException ignored) {
            if (log.isDebugEnabled())
              log.debug(
                  "Attempted to remove lock from removed entry (will retry) [rmvVer="
                      + ver
                      + ", entry="
                      + entry
                      + ']');
          }
        }
      }

      if (map == null || map.isEmpty()) return;

      Collection<GridCacheVersion> committed = ctx.tm().committedVersions(ver);
      Collection<GridCacheVersion> rolledback = ctx.tm().rolledbackVersions(ver);

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

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

        if (!req.keyBytes().isEmpty()) {
          req.completedVersions(committed, rolledback);

          // 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);
    }
  }
  /** {@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);
    }
  }
  /**
   * @param nodeId Primary node ID.
   * @param req Request.
   * @return Remote transaction.
   * @throws GridException If failed.
   * @throws GridDistributedLockCancelledException If lock has been cancelled.
   */
  @SuppressWarnings({"RedundantTypeArguments"})
  @Nullable
  public GridNearTxRemote<K, V> startRemoteTxForFinish(
      UUID nodeId, GridDhtTxFinishRequest<K, V> req)
      throws GridException, GridDistributedLockCancelledException {
    GridNearTxRemote<K, V> tx = null;

    ClassLoader ldr = ctx.deploy().globalLoader();

    if (ldr != null) {
      for (GridCacheTxEntry<K, V> txEntry : req.nearWrites()) {
        GridDistributedCacheEntry<K, V> entry = null;

        while (true) {
          try {
            entry = peekExx(txEntry.key());

            if (entry != null) {
              entry.keyBytes(txEntry.keyBytes());

              // Handle implicit locks for pessimistic transactions.
              tx = ctx.tm().tx(req.version());

              if (tx != null) {
                if (tx.local()) return null;

                if (tx.markFinalizing()) tx.addWrite(txEntry.key(), txEntry.keyBytes());
                else return null;
              } else {
                tx =
                    new GridNearTxRemote<K, V>(
                        nodeId,
                        req.nearNodeId(),
                        req.threadId(),
                        req.version(),
                        null,
                        PESSIMISTIC,
                        req.isolation(),
                        req.isInvalidate(),
                        0,
                        txEntry.key(),
                        txEntry.keyBytes(),
                        txEntry.value(),
                        txEntry.valueBytes(),
                        ctx);

                if (tx.empty()) return tx;

                tx = ctx.tm().onCreated(tx);

                if (tx == null || !ctx.tm().onStarted(tx))
                  throw new GridCacheTxRollbackException(
                      "Failed to acquire lock "
                          + "(transaction has been completed): "
                          + req.version());

                if (!tx.markFinalizing()) return null;
              }

              // Add remote candidate before reordering.
              if (txEntry.explicitVersion() == null)
                entry.addRemote(
                    req.nearNodeId(),
                    nodeId,
                    req.threadId(),
                    req.version(),
                    0,
                    tx.ec(),
                    /*tx*/ true,
                    tx.implicitSingle());

              // Remote candidates for ordered lock queuing.
              entry.addRemoteCandidates(
                  Collections.<GridCacheMvccCandidate<K>>emptyList(),
                  req.version(),
                  req.committedVersions(),
                  req.rolledbackVersions());
            }

            // Double-check in case if sender node left the grid.
            if (ctx.discovery().node(req.nearNodeId()) == null) {
              if (log.isDebugEnabled())
                log.debug("Node requesting lock left grid (lock request will be ignored): " + req);

              if (tx != null) tx.rollback();

              return null;
            }

            // Entry is legit.
            break;
          } catch (GridCacheEntryRemovedException ignored) {
            assert entry.obsoleteVersion() != null
                : "Obsolete flag not set on removed entry: " + entry;

            if (log.isDebugEnabled())
              log.debug("Received entry removed exception (will retry on renewed entry): " + entry);

            if (tx != null) {
              tx.clearEntry(entry.key());

              if (log.isDebugEnabled())
                log.debug(
                    "Cleared removed entry from remote transaction (will retry) [entry="
                        + entry
                        + ", tx="
                        + tx
                        + ']');
            }
          }
        }
      }
    } else {
      String err = "Failed to acquire deployment class loader for message: " + req;

      U.warn(log, err);

      throw new GridException(err);
    }

    return tx;
  }