private static Class<? extends ReplicationPeerStorage>
    getReplicationPeerStorageClass(Configuration conf) {
    try {
      ReplicationPeerStorageType type = ReplicationPeerStorageType.valueOf(
        conf.get(REPLICATION_PEER_STORAGE_IMPL, DEFAULT_REPLICATION_PEER_STORAGE_IMPL.name())
          .toUpperCase());
      return type.getClazz();
    } catch (IllegalArgumentException e) {
      return conf.getClass(REPLICATION_PEER_STORAGE_IMPL,
        DEFAULT_REPLICATION_PEER_STORAGE_IMPL.getClazz(), ReplicationPeerStorage.class);
    }
  }
Used to create replication storage(peer, queue) classes.
hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ReplicationStorageFactory.java