/**
   * The following test first creates a file with a few blocks. It randomly truncates the replica of
   * the last block stored in each datanode. Finally, it triggers block synchronization to
   * synchronize all stored block.
   */
  public void testBlockSynchronization() throws Exception {
    final int ORG_FILE_SIZE = 3000;
    Configuration conf = new HdfsConfiguration();
    conf.setLong(DFSConfigKeys.DFS_BLOCK_SIZE_KEY, BLOCK_SIZE);
    MiniDFSCluster cluster = null;

    try {
      cluster = new MiniDFSCluster.Builder(conf).numDataNodes(5).build();
      cluster.waitActive();

      // create a file
      DistributedFileSystem dfs = (DistributedFileSystem) cluster.getFileSystem();
      String filestr = "/foo";
      Path filepath = new Path(filestr);
      DFSTestUtil.createFile(dfs, filepath, ORG_FILE_SIZE, REPLICATION_NUM, 0L);
      assertTrue(dfs.exists(filepath));
      DFSTestUtil.waitReplication(dfs, filepath, REPLICATION_NUM);

      // get block info for the last block
      LocatedBlock locatedblock =
          TestInterDatanodeProtocol.getLastLocatedBlock(dfs.dfs.getNamenode(), filestr);
      DatanodeInfo[] datanodeinfos = locatedblock.getLocations();
      assertEquals(REPLICATION_NUM, datanodeinfos.length);

      // connect to data nodes
      DataNode[] datanodes = new DataNode[REPLICATION_NUM];
      for (int i = 0; i < REPLICATION_NUM; i++) {
        datanodes[i] = cluster.getDataNode(datanodeinfos[i].getIpcPort());
        assertTrue(datanodes[i] != null);
      }

      // verify Block Info
      ExtendedBlock lastblock = locatedblock.getBlock();
      DataNode.LOG.info("newblocks=" + lastblock);
      for (int i = 0; i < REPLICATION_NUM; i++) {
        checkMetaInfo(lastblock, datanodes[i]);
      }

      DataNode.LOG.info("dfs.dfs.clientName=" + dfs.dfs.clientName);
      cluster.getNameNodeRpc().append(filestr, dfs.dfs.clientName);

      // expire lease to trigger block recovery.
      waitLeaseRecovery(cluster);

      Block[] updatedmetainfo = new Block[REPLICATION_NUM];
      long oldSize = lastblock.getNumBytes();
      lastblock =
          TestInterDatanodeProtocol.getLastLocatedBlock(dfs.dfs.getNamenode(), filestr).getBlock();
      long currentGS = lastblock.getGenerationStamp();
      for (int i = 0; i < REPLICATION_NUM; i++) {
        updatedmetainfo[i] =
            DataNodeTestUtils.getFSDataset(datanodes[i])
                .getStoredBlock(lastblock.getBlockPoolId(), lastblock.getBlockId());
        assertEquals(lastblock.getBlockId(), updatedmetainfo[i].getBlockId());
        assertEquals(oldSize, updatedmetainfo[i].getNumBytes());
        assertEquals(currentGS, updatedmetainfo[i].getGenerationStamp());
      }

      // verify that lease recovery does not occur when namenode is in safemode
      System.out.println("Testing that lease recovery cannot happen during safemode.");
      filestr = "/foo.safemode";
      filepath = new Path(filestr);
      dfs.create(filepath, (short) 1);
      cluster.getNameNodeRpc().setSafeMode(HdfsConstants.SafeModeAction.SAFEMODE_ENTER);
      assertTrue(dfs.dfs.exists(filestr));
      DFSTestUtil.waitReplication(dfs, filepath, (short) 1);
      waitLeaseRecovery(cluster);
      // verify that we still cannot recover the lease
      LeaseManager lm = NameNodeAdapter.getLeaseManager(cluster.getNamesystem());
      assertTrue("Found " + lm.countLease() + " lease, expected 1", lm.countLease() == 1);
      cluster.getNameNodeRpc().setSafeMode(HdfsConstants.SafeModeAction.SAFEMODE_LEAVE);
    } finally {
      if (cluster != null) {
        cluster.shutdown();
      }
    }
  }