/** {@inheritDoc} */
  @Override
  public Map<K, V> peekAll(
      @Nullable Collection<? extends K> keys, @Nullable Collection<GridCachePeekMode> modes)
      throws GridException {
    if (keys == null || keys.isEmpty()) return emptyMap();

    final Collection<K> skipped = new GridLeanSet<K>();

    final Map<K, V> map =
        !modes.contains(PARTITIONED_ONLY)
            ? peekAll0(keys, modes, ctx.tm().localTxx(), skipped)
            : new GridLeanMap<K, V>(0);

    if (map.size() != keys.size() && !modes.contains(NEAR_ONLY)) {
      map.putAll(
          dht.peekAll(
              F.view(
                  keys,
                  new P1<K>() {
                    @Override
                    public boolean apply(K k) {
                      return !map.containsKey(k) && !skipped.contains(k);
                    }
                  }),
              modes));
    }

    return map;
  }
  /**
   * First positive integer that is not present in started set.
   *
   * @param started Already started indices.
   * @return First positive integer that is not present in started set.
   */
  private int nextIndex(Collection<Integer> started) {
    assert started.contains(0);

    for (int i = 1; i < 10000; i++) {
      if (!started.contains(i)) return i;
    }

    throw new IllegalStateException();
  }
  /** {@inheritDoc} */
  @Override
  public V peek(K key, @Nullable Collection<GridCachePeekMode> modes) throws GridException {
    V val = null;

    if (!modes.contains(PARTITIONED_ONLY)) {
      try {
        val = peek0(true, key, modes, ctx.tm().txx());
      } catch (GridCacheFilterFailedException ignored) {
        if (log.isDebugEnabled()) log.debug("Filter validation failed for key: " + key);

        return null;
      }
    }

    return val == null && !modes.contains(NEAR_ONLY) ? dht.peek(key, modes) : val;
  }
  /** {@inheritDoc} */
  @Override
  public void execute(@Nullable GridProjection prj) throws GridException {
    if (cb == null)
      throw new IllegalStateException("Mandatory local callback is not set for the query: " + this);

    if (prj == null) prj = ctx.grid();

    prj = prj.forCache(ctx.name());

    if (prj.nodes().isEmpty())
      throw new GridTopologyException("Failed to execute query (projection is empty): " + this);

    GridCacheMode mode = ctx.config().getCacheMode();

    if (mode == LOCAL || mode == REPLICATED) {
      Collection<GridNode> nodes = prj.nodes();

      GridNode node = nodes.contains(ctx.localNode()) ? ctx.localNode() : F.rand(nodes);

      assert node != null;

      if (nodes.size() > 1 && !ctx.cache().isDrSystemCache()) {
        if (node.id().equals(ctx.localNodeId()))
          U.warn(
              log,
              "Continuous query for "
                  + mode
                  + " cache can be run only on local node. "
                  + "Will execute query locally: "
                  + this);
        else
          U.warn(
              log,
              "Continuous query for "
                  + mode
                  + " cache can be run only on single node. "
                  + "Will execute query on remote node [qry="
                  + this
                  + ", node="
                  + node
                  + ']');
      }

      prj = prj.forNode(node);
    }

    closeLock.lock();

    try {
      if (routineId != null)
        throw new IllegalStateException("Continuous query can't be executed twice.");

      guard.block();

      GridContinuousHandler hnd =
          new GridCacheContinuousQueryHandler<>(ctx.name(), topic, cb, filter, prjPred);

      routineId =
          ctx.kernalContext()
              .continuous()
              .startRoutine(hnd, bufSize, timeInterval, autoUnsubscribe, prj.predicate())
              .get();
    } finally {
      closeLock.unlock();
    }
  }