@Override
  public SettableFuture<ConfigTaskResult> showDatabases(
      final ShowDB showDB, final Predicate<String> canSeenDB) {
    final SettableFuture<ConfigTaskResult> future = SettableFuture.create();
    // Construct request using statement
    final List<String> databasePathPattern = Arrays.asList(ALL_RESULT_NODES);
    try (final ConfigNodeClient client =
        CONFIG_NODE_CLIENT_MANAGER.borrowClient(ConfigNodeInfo.CONFIG_REGION_ID)) {
      // Send request to some API server
      final TGetDatabaseReq req =
          new TGetDatabaseReq(databasePathPattern, ALL_MATCH_SCOPE.serialize())
              .setIsTableModel(true);
      final TShowDatabaseResp resp = client.showDatabase(req);
      // build TSBlock
      ShowDBTask.buildTSBlock(resp.getDatabaseInfoMap(), future, showDB.isDetails(), canSeenDB);
    } catch (final IOException | ClientManagerException | TException e) {
      future.setException(e);
    }
    return future;
  }
FIXME Consolidate this clientManager with the upper one.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/execution/config/executor/ClusterConfigTaskExecutor.java