How to use

set

method

in

org.apache.hadoop.hdfs.server.namenode.SaveNamespaceContext

void saveFSImage(String dest, DataOutputStream fstream) throws IOException { 
 saveNamespaceContext.set(namesystem, editLog.getLastWrittenTxId());
 FSImageFormat.Saver saver = new FSImageFormat.Saver(saveNamespaceContext);
 FSImageCompression compression = FSImageCompression.createCompression(namesystem.getConf(), false);
 saver.save(new File(dest), compression, fstream);
}

/** Create new dfs name directory.  Caution: this destroys all files
 * in this filesystem. */
void format(StorageDirectory sd) throws IOException {
 saveNamespaceContext.set(namesystem, -1);
 sd.clearDirectory(); // create currrent dir
 sd.lock();
 try {
  saveCurrent(saveNamespaceContext, sd, false);
 } finally {
  sd.unlock();
 }
 LOG.info("Storage directory " + sd.getRoot()
      + " has been successfully formatted.");
}

this.checkpointTime = FSNamesystem.now();
List<Thread> savers = new ArrayList<Thread>();
saveNamespaceContext.set(namesystem, editLog.getLastWrittenTxId());

attemptRestoreRemovedStorage();
saveNamespaceContext.set(namesystem, editLog.getLastWrittenTxId());