// rename bar --> bar2
final Path bar2 = new Path(foo, "bar2");
hdfs.rename(bar, bar2);
// append file and keep it as underconstruction.
FSDataOutputStream out = hdfs.append(bar2);
out.writeByte(0);
((DFSOutputStream) out.getWrappedStream()).hsync(
EnumSet.of(SyncFlag.UPDATE_LENGTH));
// save namespace and restart
restartClusterAndCheckImage(true);