Blocker Description
The dfs configuration checks we now perform to support hdfs WALs includes a check for dfs.datanode.synconclose which informs the datanode to flush to disk when a file is closed instead of lazily writing the block (very important in the case of power failure).
Looking at the actual check, it performs reflection on a CreateFlag class. In Apache Hadoop 1.2.1, this class doesn't exist yet the option for dfs.datanode.synconclose does exist. We should likely just reflect on the constant DFSConfigKeys.DFS_DATANODE_SYNCONCLOSE_KEY or DFSConfigKeys.DFS_DATANODE_SYNCONCLOSE_DEFAULT to determine if that option is present.