@Override
  protected void doInit(WALFactory factory, Configuration conf, String providerId)
    throws IOException {
    this.providerId = providerId;
    // get log prefix
    StringBuilder sb = new StringBuilder().append(factory.factoryId);
    if (providerId != null) {
      if (providerId.startsWith(WAL_FILE_NAME_DELIMITER)) {
        sb.append(providerId);
      } else {
        sb.append(WAL_FILE_NAME_DELIMITER).append(providerId);
      }
    }
    logPrefix = sb.toString();
    doInit(conf);
  }
@param factory    factory that made us, identity used for FS layout. may not be null
@param conf       may not be null
@param providerId differentiate between providers from one factory, used for FS layout. may be
                  null
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractFSWALProvider.java