/**
   * Test that, when a block is re-opened for append, the related datanode messages are correctly
   * queued by the SBN because they have future states and genstamps.
   */
  @Test
  public void testQueueingWithAppend() throws Exception {
    int numQueued = 0;
    int numDN = cluster.getDataNodes().size();

    FSDataOutputStream out = fs.create(TEST_FILE_PATH);
    try {
      AppendTestUtil.write(out, 0, 10);
      out.hflush();

      // Opening the file will report RBW replicas, but will be
      // queued on the StandbyNode.
      numQueued += numDN; // RBW messages
    } finally {
      IOUtils.closeStream(out);
      numQueued += numDN; // blockReceived messages
    }

    cluster.triggerBlockReports();
    numQueued += numDN;

    try {
      out = fs.append(TEST_FILE_PATH);
      AppendTestUtil.write(out, 10, 10);
      // RBW replicas once it's opened for append
      numQueued += numDN;

    } finally {
      IOUtils.closeStream(out);
      numQueued += numDN; // blockReceived
    }

    cluster.triggerBlockReports();
    numQueued += numDN;

    assertEquals(
        numQueued, cluster.getNameNode(1).getNamesystem().getPendingDataNodeMessageCount());

    cluster.transitionToStandby(0);
    cluster.transitionToActive(1);

    // Verify that no replicas are marked corrupt, and that the
    // file is readable from the failed-over standby.
    BlockManagerTestUtil.updateState(nn1.getNamesystem().getBlockManager());
    BlockManagerTestUtil.updateState(nn2.getNamesystem().getBlockManager());
    assertEquals(0, nn1.getNamesystem().getCorruptReplicaBlocks());
    assertEquals(0, nn2.getNamesystem().getCorruptReplicaBlocks());

    AppendTestUtil.check(fs, TEST_FILE_PATH, 20);
  }