@Override
  public void init(Configuration config, String providerId) {
    this.providerId = providerId;
  }
A WAL grouping strategy based on namespace. Notice: the wal-group mapping might change if we
support dynamic namespace updating later, and special attention needed if we support feature like
group-based replication.
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/NamespaceGroupingStrategy.java