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OpenStack Study: __init__.py**** CubicPower OpenStack Study **** def _load_strategies(): """Load all strategy modules.""" modules = {} namespace = "glance.common.image_location_strategy.modules" ex = stevedore.extension.ExtensionManager(namespace) for module_name in ex.names(): try: mgr = stevedore.driver.DriverManager( namespace=namespace, name=module_name, invoke_on_load=False) # Obtain module name strategy_name = str(mgr.driver.get_strategy_name()) if strategy_name in modules: msg = (_('%(strategy)s is registered as a module twice. ' '%(module)s is not being used.') % {'strategy': strategy_name, 'module': module_name}) LOG.warn(msg) else: # Initialize strategy module mgr.driver.init() modules[strategy_name] = mgr.driver except Exception as e: LOG.error(_("Failed to load location strategy module " "%(module)s: %(e)s") % {'module': module_name, 'e': e}) return modules _available_strategies = _load_strategies()
**** CubicPower OpenStack Study **** def verify_location_strategy(conf=None, strategies=_available_strategies): """Validate user configured 'location_strategy' option value.""" if not conf: conf = CONF.location_strategy if conf not in strategies: msg = (_('Invalid location_strategy option: %(name)s. ' 'The valid strategy option(s) is(are): %(strategies)s') % {'name': conf, 'strategies': ", ".join(strategies.keys())}) LOG.error(msg) raise RuntimeError(msg)
**** CubicPower OpenStack Study **** def get_ordered_locations(locations, **kwargs): """ Order image location list by configured strategy. :param locations: The original image location list. :param kwargs: Strategy-specific arguments for under layer strategy module. :return: The image location list with strategy-specific order. """ if not locations: return [] strategy_module = _available_strategies[CONF.location_strategy] return strategy_module.get_ordered_locations(copy.deepcopy(locations), **kwargs)
**** CubicPower OpenStack Study **** def choose_best_location(locations, **kwargs): """ Choose best location from image location list by configured strategy. :param locations: The original image location list. :param kwargs: Strategy-specific arguments for under layer strategy module. :return: The best location from image location list. """ locations = get_ordered_locations(locations, **kwargs) if locations: return locations[0] else: return None
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