code: public void put(String key, Object value) {
          // acquire write lock
          writeLock.lock();
          try {
              if(METADATA_KEYS.contains(key)) {
                  VectorClock version = (VectorClock) get(key, null).get(0).getVersion();
                  put(key,
                      new Versioned<Object>(value, version.incremented(getNodeId(),
                                                                       System.currentTimeMillis())));
              } else {
                  throw new VoldemortException("Unhandled Key:" + key + " for MetadataStore put()");
              }
          } finally {
              writeLock.unlock();
          }
      }
docs: helper function to read current version and put() after incrementing it
  for local node.
  
  @param key
  @param value