@Override
 public boolean seekToNewSource(long targetPos) throws IOException {
   boolean res;
   try {
     res = in.seekToNewSource(targetPos);
   } catch (FileNotFoundException e) {
     res = tryOpen().seekToNewSource(targetPos);
   } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
     res = tryOpen().seekToNewSource(targetPos);
   } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
     res = tryOpen().seekToNewSource(targetPos);
   }
   if (res) pos = targetPos;
   return res;
 }
  protected void doTestRead(Configuration conf, MiniDFSCluster cluster, boolean isStriped)
      throws Exception {
    final int numDataNodes = cluster.getDataNodes().size();
    final NameNode nn = cluster.getNameNode();
    final NamenodeProtocols nnProto = nn.getRpcServer();
    final BlockManager bm = nn.getNamesystem().getBlockManager();
    final BlockTokenSecretManager sm = bm.getBlockTokenSecretManager();

    // set a short token lifetime (1 second) initially
    SecurityTestUtil.setBlockTokenLifetime(sm, 1000L);

    Path fileToRead = new Path(FILE_TO_READ);
    FileSystem fs = cluster.getFileSystem();
    byte[] expected = generateBytes(FILE_SIZE);
    createFile(fs, fileToRead, expected);

    /*
     * setup for testing expiration handling of cached tokens
     */

    // read using blockSeekTo(). Acquired tokens are cached in in1
    FSDataInputStream in1 = fs.open(fileToRead);
    assertTrue(checkFile1(in1, expected));
    // read using blockSeekTo(). Acquired tokens are cached in in2
    FSDataInputStream in2 = fs.open(fileToRead);
    assertTrue(checkFile1(in2, expected));
    // read using fetchBlockByteRange(). Acquired tokens are cached in in3
    FSDataInputStream in3 = fs.open(fileToRead);
    assertTrue(checkFile2(in3, expected));

    /*
     * testing READ interface on DN using a BlockReader
     */
    DFSClient client = null;
    try {
      client = new DFSClient(new InetSocketAddress("localhost", cluster.getNameNodePort()), conf);
    } finally {
      if (client != null) client.close();
    }
    List<LocatedBlock> locatedBlocks =
        nnProto.getBlockLocations(FILE_TO_READ, 0, FILE_SIZE).getLocatedBlocks();
    LocatedBlock lblock = locatedBlocks.get(0); // first block
    // verify token is not expired
    assertFalse(isBlockTokenExpired(lblock));
    // read with valid token, should succeed
    tryRead(conf, lblock, true);

    /*
     * wait till myToken and all cached tokens in in1, in2 and in3 expire
     */

    while (!isBlockTokenExpired(lblock)) {
      try {
        Thread.sleep(10);
      } catch (InterruptedException ignored) {
      }
    }

    /*
     * continue testing READ interface on DN using a BlockReader
     */

    // verify token is expired
    assertTrue(isBlockTokenExpired(lblock));
    // read should fail
    tryRead(conf, lblock, false);
    // use a valid new token
    bm.setBlockToken(lblock, BlockTokenIdentifier.AccessMode.READ);
    // read should succeed
    tryRead(conf, lblock, true);
    // use a token with wrong blockID
    long rightId = lblock.getBlock().getBlockId();
    long wrongId = rightId + 1;
    lblock.getBlock().setBlockId(wrongId);
    bm.setBlockToken(lblock, BlockTokenIdentifier.AccessMode.READ);
    lblock.getBlock().setBlockId(rightId);
    // read should fail
    tryRead(conf, lblock, false);
    // use a token with wrong access modes
    bm.setBlockToken(lblock, BlockTokenIdentifier.AccessMode.WRITE);
    // read should fail
    tryRead(conf, lblock, false);

    // set a long token lifetime for future tokens
    SecurityTestUtil.setBlockTokenLifetime(sm, 600 * 1000L);

    /*
     * testing that when cached tokens are expired, DFSClient will re-fetch
     * tokens transparently for READ.
     */

    // confirm all tokens cached in in1 are expired by now
    List<LocatedBlock> lblocks = DFSTestUtil.getAllBlocks(in1);
    for (LocatedBlock blk : lblocks) {
      assertTrue(isBlockTokenExpired(blk));
    }
    // verify blockSeekTo() is able to re-fetch token transparently
    in1.seek(0);
    assertTrue(checkFile1(in1, expected));

    // confirm all tokens cached in in2 are expired by now
    List<LocatedBlock> lblocks2 = DFSTestUtil.getAllBlocks(in2);
    for (LocatedBlock blk : lblocks2) {
      assertTrue(isBlockTokenExpired(blk));
    }
    // verify blockSeekTo() is able to re-fetch token transparently (testing
    // via another interface method)
    if (isStriped) {
      // striped block doesn't support seekToNewSource
      in2.seek(0);
    } else {
      assertTrue(in2.seekToNewSource(0));
    }
    assertTrue(checkFile1(in2, expected));

    // confirm all tokens cached in in3 are expired by now
    List<LocatedBlock> lblocks3 = DFSTestUtil.getAllBlocks(in3);
    for (LocatedBlock blk : lblocks3) {
      assertTrue(isBlockTokenExpired(blk));
    }
    // verify fetchBlockByteRange() is able to re-fetch token transparently
    assertTrue(checkFile2(in3, expected));

    /*
     * testing that after datanodes are restarted on the same ports, cached
     * tokens should still work and there is no need to fetch new tokens from
     * namenode. This test should run while namenode is down (to make sure no
     * new tokens can be fetched from namenode).
     */

    // restart datanodes on the same ports that they currently use
    assertTrue(cluster.restartDataNodes(true));
    cluster.waitActive();
    assertEquals(numDataNodes, cluster.getDataNodes().size());
    cluster.shutdownNameNode(0);

    // confirm tokens cached in in1 are still valid
    lblocks = DFSTestUtil.getAllBlocks(in1);
    for (LocatedBlock blk : lblocks) {
      assertFalse(isBlockTokenExpired(blk));
    }
    // verify blockSeekTo() still works (forced to use cached tokens)
    in1.seek(0);
    assertTrue(checkFile1(in1, expected));

    // confirm tokens cached in in2 are still valid
    lblocks2 = DFSTestUtil.getAllBlocks(in2);
    for (LocatedBlock blk : lblocks2) {
      assertFalse(isBlockTokenExpired(blk));
    }

    // verify blockSeekTo() still works (forced to use cached tokens)
    if (isStriped) {
      in2.seek(0);
    } else {
      in2.seekToNewSource(0);
    }
    assertTrue(checkFile1(in2, expected));

    // confirm tokens cached in in3 are still valid
    lblocks3 = DFSTestUtil.getAllBlocks(in3);
    for (LocatedBlock blk : lblocks3) {
      assertFalse(isBlockTokenExpired(blk));
    }
    // verify fetchBlockByteRange() still works (forced to use cached tokens)
    assertTrue(checkFile2(in3, expected));

    /*
     * testing that when namenode is restarted, cached tokens should still
     * work and there is no need to fetch new tokens from namenode. Like the
     * previous test, this test should also run while namenode is down. The
     * setup for this test depends on the previous test.
     */

    // restart the namenode and then shut it down for test
    cluster.restartNameNode(0);
    cluster.shutdownNameNode(0);

    // verify blockSeekTo() still works (forced to use cached tokens)
    in1.seek(0);
    assertTrue(checkFile1(in1, expected));
    // verify again blockSeekTo() still works (forced to use cached tokens)
    if (isStriped) {
      in2.seek(0);
    } else {
      in2.seekToNewSource(0);
    }
    assertTrue(checkFile1(in2, expected));

    // verify fetchBlockByteRange() still works (forced to use cached tokens)
    assertTrue(checkFile2(in3, expected));

    /*
     * testing that after both namenode and datanodes got restarted (namenode
     * first, followed by datanodes), DFSClient can't access DN without
     * re-fetching tokens and is able to re-fetch tokens transparently. The
     * setup of this test depends on the previous test.
     */

    // restore the cluster and restart the datanodes for test
    cluster.restartNameNode(0);
    assertTrue(cluster.restartDataNodes(true));
    cluster.waitActive();
    assertEquals(numDataNodes, cluster.getDataNodes().size());

    // shutdown namenode so that DFSClient can't get new tokens from namenode
    cluster.shutdownNameNode(0);

    // verify blockSeekTo() fails (cached tokens become invalid)
    in1.seek(0);
    assertFalse(checkFile1(in1, expected));
    // verify fetchBlockByteRange() fails (cached tokens become invalid)
    assertFalse(checkFile2(in3, expected));

    // restart the namenode to allow DFSClient to re-fetch tokens
    cluster.restartNameNode(0);
    // verify blockSeekTo() works again (by transparently re-fetching
    // tokens from namenode)
    in1.seek(0);
    assertTrue(checkFile1(in1, expected));
    if (isStriped) {
      in2.seek(0);
    } else {
      in2.seekToNewSource(0);
    }
    assertTrue(checkFile1(in2, expected));
    // verify fetchBlockByteRange() works again (by transparently
    // re-fetching tokens from namenode)
    assertTrue(checkFile2(in3, expected));

    /*
     * testing that when datanodes are restarted on different ports, DFSClient
     * is able to re-fetch tokens transparently to connect to them
     */

    // restart datanodes on newly assigned ports
    assertTrue(cluster.restartDataNodes(false));
    cluster.waitActive();
    assertEquals(numDataNodes, cluster.getDataNodes().size());
    // verify blockSeekTo() is able to re-fetch token transparently
    in1.seek(0);
    assertTrue(checkFile1(in1, expected));
    // verify blockSeekTo() is able to re-fetch token transparently
    if (isStriped) {
      in2.seek(0);
    } else {
      in2.seekToNewSource(0);
    }
    assertTrue(checkFile1(in2, expected));
    // verify fetchBlockByteRange() is able to re-fetch token transparently
    assertTrue(checkFile2(in3, expected));
  }