def get_aggregate (config):
    """Get an aggregator instance with given configuration."""
    _urlqueue = urlqueue.UrlQueue(max_allowed_urls=config["maxnumurls"])
    _robots_txt = robots_txt.RobotsTxt(config["useragent"])
    plugin_manager = plugins.PluginManager(config)
    result_cache = results.ResultCache()
    return aggregator.Aggregate(config, _urlqueue, _robots_txt, plugin_manager,
        result_cache)