public void notifyAllObservers(Configuration conf) {
    LOG.info("Starting to notify all observers that config changed.");
    synchronized (configurationObservers) {
      for (ConfigurationObserver observer : configurationObservers) {
        try {
          if (observer != null) {
            observer.onConfigurationChange(conf);
          }
        } catch (Throwable t) {
          LOG.error("Encountered a throwable while notifying observers: of type : {}({})",
            observer.getClass().getCanonicalName(), observer, t);
        }
      }
    }
  }
The conf object has been repopulated from disk, and we have to notify all the observers that
are expressed interest to do that.
hbase-common/src/main/java/org/apache/hadoop/hbase/conf/ConfigurationManager.java