@Override
      public TableDescriptor get() throws IOException {
        TableDescriptor old = getTableDescriptors().get(tableName);
        if (old.hasColumnFamily(column.getName())) {
          throw new InvalidFamilyOperationException("Column family '" + column.getNameAsString()
            + "' in table '" + tableName + "' already exists so cannot be added");
        }

        return TableDescriptorBuilder.newBuilder(old).setColumnFamily(column).build();
      }
Switch for the background CatalogJanitor thread. Used for testing. The thread will continue to
run. It will just be a noop if disabled.
@param b If false, the catalog janitor won't do anything.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java