public DPageDB (String dirname, PageCatcher catcher) {
super(dirname);
Config config = Config.getConfig("crawler.properties");
nodes = getNodeList(config);
localNode = getLocalNode(nodes);
APageMapper mapper = getPageMapper(config, nodes.size());
pageCatcher = catcher;
pageCatcher.start(localNode);
distributor = new PageDistributor(nodes, localNode, mapper);
}