@Override
  protected WAL getWAL0(RegionInfo region) throws IOException {
    String group;
    if (META_WAL_PROVIDER_ID.equals(this.providerId)) {
      group = META_WAL_GROUP_NAME;
    } else {
      byte[] id;
      byte[] namespace;
      if (region != null) {
        id = region.getEncodedNameAsBytes();
        namespace = region.getTable().getNamespace();
      } else {
        id = HConstants.EMPTY_BYTE_ARRAY;
        namespace = null;
      }
      group = strategy.group(id, namespace);
    }
    return getWAL(group);
  }
A group-provider mapping, make sure one-one rather than many-one mapping
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/RegionGroupingProvider.java