private static void decorateRegionConfiguration(Configuration conf) {
    if (ReplicationUtils.isReplicationForBulkLoadDataEnabled(conf)) {
      String plugins = conf.get(CoprocessorHost.REGION_COPROCESSOR_CONF_KEY, "");
      String replicationCoprocessorClass = ReplicationObserver.class.getCanonicalName();
      if (!plugins.contains(replicationCoprocessorClass)) {
        conf.set(CoprocessorHost.REGION_COPROCESSOR_CONF_KEY,
          (plugins.equals("") ? "" : (plugins + ",")) + replicationCoprocessorClass);
      }
    }
  }
This method modifies the region's configuration in order to inject replication-related features
@param conf region configurations
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java