/**
   * Cache preloader should call this method within partition lock.
   *
   * @param key Key.
   * @param ver Version.
   * @return {@code True} if preloading is permitted.
   */
  public boolean preloadingPermitted(KeyCacheObject key, GridCacheVersion ver) {
    assert key != null;
    assert ver != null;
    assert lock.isHeldByCurrentThread(); // Only one thread can enter this method at a time.

    if (state() != MOVING) return false;

    Map<KeyCacheObject, GridCacheVersion> evictHist0 = evictHist;

    if (evictHist0 != null) {
      GridCacheVersion ver0 = evictHist0.get(key);

      // Permit preloading if version in history
      // is missing or less than passed in.
      return ver0 == null || ver0.isLess(ver);
    }

    return false;
  }
  /**
   * @param key Key.
   * @param ver Version.
   */
  public void onEntryEvicted(KeyCacheObject key, GridCacheVersion ver) {
    assert key != null;
    assert ver != null;
    assert lock.isHeldByCurrentThread(); // Only one thread can enter this method at a time.

    if (state() != MOVING) return;

    Map<KeyCacheObject, GridCacheVersion> evictHist0 = evictHist;

    if (evictHist0 != null) {
      GridCacheVersion ver0 = evictHist0.get(key);

      if (ver0 == null || ver0.isLess(ver)) {
        GridCacheVersion ver1 = evictHist0.put(key, ver);

        assert ver1 == ver0;
      }
    }
  }
  /** {@inheritDoc} */
  @Override
  public int compareTo(GridCacheMvccCandidate<K> o) {
    if (o == this) return 0;

    int c = ver.compareTo(o.ver);

    // This is done, so compare and equals methods will be consistent.
    if (c == 0) return key().equals(o.key()) ? 0 : id < o.id ? -1 : 1;

    return c;
  }
  /** {@inheritDoc} */
  @SuppressWarnings({"unchecked"})
  @Override
  public boolean equals(Object o) {
    if (o == null) return false;

    if (o == this) return true;

    GridCacheMvccCandidate<K> other = (GridCacheMvccCandidate<K>) o;

    assert key() != null && other.key() != null
        : "Key is null [this=" + this + ", other=" + o + ']';

    return ver.equals(other.ver) && key().equals(other.key());
  }
  /**
   * @param nodeId Sender node id.
   * @param msg Single partition info.
   */
  public void onReceive(final UUID nodeId, final GridDhtPartitionsSingleMessage msg) {
    assert msg != null;

    assert msg.exchangeId().equals(exchId);

    // Update last seen version.
    while (true) {
      GridCacheVersion old = lastVer.get();

      if (old == null || old.compareTo(msg.lastVersion()) < 0) {
        if (lastVer.compareAndSet(old, msg.lastVersion())) break;
      } else break;
    }

    if (isDone()) {
      if (log.isDebugEnabled())
        log.debug(
            "Received message for finished future (will reply only to sender) [msg="
                + msg
                + ", fut="
                + this
                + ']');

      sendAllPartitions(nodeId, cctx.gridConfig().getNetworkSendRetryCount());
    } else {
      initFut.listen(
          new CI1<IgniteInternalFuture<Boolean>>() {
            @Override
            public void apply(IgniteInternalFuture<Boolean> t) {
              try {
                if (!t.get()) // Just to check if there was an error.
                return;

                ClusterNode loc = cctx.localNode();

                singleMsgs.put(nodeId, msg);

                boolean match = true;

                // Check if oldest node has changed.
                if (!oldestNode.get().equals(loc)) {
                  match = false;

                  synchronized (mux) {
                    // Double check.
                    if (oldestNode.get().equals(loc)) match = true;
                  }
                }

                if (match) {
                  boolean allReceived;

                  synchronized (rcvdIds) {
                    if (rcvdIds.add(nodeId)) updatePartitionSingleMap(msg);

                    allReceived = allReceived();
                  }

                  // If got all replies, and initialization finished, and reply has not been sent
                  // yet.
                  if (allReceived && ready.get() && replied.compareAndSet(false, true)) {
                    spreadPartitions();

                    onDone(exchId.topologyVersion());
                  } else if (log.isDebugEnabled())
                    log.debug(
                        "Exchange future full map is not sent [allReceived="
                            + allReceived()
                            + ", ready="
                            + ready
                            + ", replied="
                            + replied.get()
                            + ", init="
                            + init.get()
                            + ", fut="
                            + this
                            + ']');
                }
              } catch (IgniteCheckedException e) {
                U.error(log, "Failed to initialize exchange future: " + this, e);
              }
            }
          });
    }
  }
  /** {@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);
    }
  }
 /** {@inheritDoc} */
 @Override
 public int hashCode() {
   return ver.hashCode();
 }
 /**
  * Checks if this candidate matches version or thread-nodeId combination.
  *
  * @param nodeId Node ID to check.
  * @param ver Version to check.
  * @param threadId Thread ID to check.
  * @return {@code True} if matched.
  */
 public boolean matches(GridCacheVersion ver, UUID nodeId, long threadId) {
   return ver.equals(this.ver) || (nodeId.equals(this.nodeId) && threadId == this.threadId);
 }