/** @return Nodes to execute on. */
  private Collection<GridNode> nodes() {
    GridCacheMode cacheMode = cctx.config().getCacheMode();

    switch (cacheMode) {
      case LOCAL:
        if (prj != null)
          U.warn(
              log,
              "Ignoring query projection because it's executed over LOCAL cache "
                  + "(only local node will be queried): "
                  + this);

        return Collections.singletonList(cctx.localNode());

      case REPLICATED:
        if (prj != null) return nodes(cctx, prj);

        GridCacheDistributionMode mode = cctx.config().getDistributionMode();

        return mode == PARTITIONED_ONLY || mode == NEAR_PARTITIONED
            ? Collections.singletonList(cctx.localNode())
            : Collections.singletonList(F.rand(nodes(cctx, null)));

      case PARTITIONED:
        return nodes(cctx, prj);

      default:
        throw new IllegalStateException("Unknown cache distribution mode: " + cacheMode);
    }
  }
  /** @return Nodes to execute on. */
  private Collection<ClusterNode> nodes() {
    CacheMode cacheMode = cctx.config().getCacheMode();

    switch (cacheMode) {
      case LOCAL:
        if (prj != null)
          U.warn(
              log,
              "Ignoring query projection because it's executed over LOCAL cache "
                  + "(only local node will be queried): "
                  + this);

        return Collections.singletonList(cctx.localNode());

      case REPLICATED:
        if (prj != null || partition() != null) return nodes(cctx, prj, partition());

        return cctx.affinityNode()
            ? Collections.singletonList(cctx.localNode())
            : Collections.singletonList(F.rand(nodes(cctx, null, partition())));

      case PARTITIONED:
        return nodes(cctx, prj, partition());

      default:
        throw new IllegalStateException("Unknown cache distribution mode: " + cacheMode);
    }
  }
  /** @throws Exception If failed. */
  public void testEmptyProjections() throws Exception {
    final GridClientCompute dflt = client.compute();

    Collection<? extends GridClientNode> nodes = dflt.nodes();

    assertEquals(NODES_CNT, nodes.size());

    Iterator<? extends GridClientNode> iter = nodes.iterator();

    final GridClientCompute singleNodePrj = dflt.projection(Collections.singletonList(iter.next()));

    final GridClientNode second = iter.next();

    final GridClientPredicate<GridClientNode> noneFilter =
        new GridClientPredicate<GridClientNode>() {
          @Override
          public boolean apply(GridClientNode node) {
            return false;
          }
        };

    final GridClientPredicate<GridClientNode> targetFilter =
        new GridClientPredicate<GridClientNode>() {
          @Override
          public boolean apply(GridClientNode node) {
            return node.nodeId().equals(second.nodeId());
          }
        };

    GridTestUtils.assertThrows(
        log(),
        new Callable<Object>() {
          @Override
          public Object call() throws Exception {
            return dflt.projection(noneFilter).log(-1, -1);
          }
        },
        GridServerUnreachableException.class,
        null);

    GridTestUtils.assertThrows(
        log(),
        new Callable<Object>() {
          @Override
          public Object call() throws Exception {
            return singleNodePrj.projection(second);
          }
        },
        GridClientException.class,
        null);

    GridTestUtils.assertThrows(
        log(),
        new Callable<Object>() {
          @Override
          public Object call() throws Exception {
            return singleNodePrj.projection(targetFilter);
          }
        },
        GridClientException.class,
        null);
  }
  /** Initializes future. */
  public void prepare() {
    if (log.isDebugEnabled())
      log.debug("Checking if transaction was committed on remote nodes: " + tx);

    // Check local node first (local node can be a backup node for some part of this transaction).
    long originatingThreadId = tx.threadId();

    if (tx instanceof GridCacheTxRemoteEx)
      originatingThreadId = ((GridCacheTxRemoteEx) tx).remoteThreadId();

    GridCacheCommittedTxInfo<K, V> txInfo =
        cctx.tm().txCommitted(tx.nearXidVersion(), tx.eventNodeId(), originatingThreadId);

    if (txInfo != null) {
      onDone(txInfo);

      markInitialized();

      return;
    }

    Collection<GridNode> checkNodes = CU.remoteNodes(cctx, tx.topologyVersion());

    if (tx instanceof GridDhtTxRemote) {
      // If we got primary node failure and near node has not failed.
      if (tx.nodeId().equals(failedNodeId) && !tx.eventNodeId().equals(failedNodeId)) {
        nearCheck = true;

        GridNode nearNode = cctx.discovery().node(tx.eventNodeId());

        if (nearNode == null) {
          // Near node failed, separate check prepared future will take care of it.
          onDone(
              new GridTopologyException(
                  "Failed to check near transaction state (near node left grid): "
                      + tx.eventNodeId()));

          return;
        }

        checkNodes = Collections.singletonList(nearNode);
      }
    }

    for (GridNode rmtNode : checkNodes) {
      // Skip left nodes and local node.
      if (rmtNode.id().equals(failedNodeId)) continue;

      /*
       * Send message to all cache nodes in the topology.
       */

      MiniFuture fut = new MiniFuture(rmtNode.id());

      GridCachePessimisticCheckCommittedTxRequest<K, V> req =
          new GridCachePessimisticCheckCommittedTxRequest<>(
              tx, originatingThreadId, futureId(), fut.futureId());

      add(fut);

      try {
        cctx.io().send(rmtNode.id(), req);
      } catch (GridTopologyException ignored) {
        fut.onNodeLeft();
      } catch (GridException e) {
        fut.onError(e);

        break;
      }
    }

    markInitialized();
  }