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OpenStack Study: __init__.py**** CubicPower OpenStack Study **** def _image_handler_asso(handler, path, location, image_meta): _IMAGE_HANDLERS_ASSO[path] = (handler, location, image_meta)
**** CubicPower OpenStack Study **** def _image_handler_disasso(handler, path): _IMAGE_HANDLERS_ASSO.pop(path, None)
**** CubicPower OpenStack Study **** def _match_locations(locations, schemes): matched = [] if locations and (schemes is not None): for loc in locations: # Note(zhiyan): location = {'url': 'string', # 'metadata': {...}} if len(schemes) == 0: # Note(zhiyan): handler has not scheme limitation. matched.append(loc) elif urlparse.urlparse(loc['url']).scheme in schemes: matched.append(loc) return matched
**** CubicPower OpenStack Study **** def load_image_handlers(driver): """Loading construct user configured image handlers. Handler objects will be cached to keep handler instance as singleton since this structure need support follow sub-class development, developer could implement particular sub-class in relevant hypervisor layer with more advanced functions. The handler's __init__() need do some re-preparing work if it needed, for example when nova-compute service restart or host reboot, CinderImageHandler will need to re-prepare iscsi/fc link for volumes those already be cached on compute host as template image previously. """ global _IMAGE_HANDLERS, _IMAGE_HANDLERS_ASSO if _IMAGE_HANDLERS: _IMAGE_HANDLERS = [] _IMAGE_HANDLERS_ASSO = {} # for de-duplicate. using ordereddict lib to support both py26 and py27? processed_handler_names = [] ex = stevedore.extension.ExtensionManager('nova.virt.image.handlers') for name in CONF.image_handlers: if not name: continue name = name.strip() if name in processed_handler_names: LOG.warn(_("Duplicated handler extension name in 'image_handlers' " "option: %s, skip."), name) continue elif name not in ex.names(): LOG.warn(_("Invalid handler extension name in 'image_handlers' " "option: %s, skip."), name) continue processed_handler_names.append(name) try: mgr = stevedore.driver.DriverManager( namespace='nova.virt.image.handlers', name=name, invoke_on_load=True, invoke_kwds={"driver": driver, "associate_fn": _image_handler_asso, "disassociate_fn": _image_handler_disasso}) _IMAGE_HANDLERS.append(mgr.driver) except Exception as err: LOG.warn(_("Failed to import image handler extension " "%(name)s: %(err)s"), {'name': name, 'err': err})
**** CubicPower OpenStack Study **** def handle_image(context=None, image_id=None, user_id=None, project_id=None, target_path=None): """Handle image using available handles. This generator will return each available handler on each time. :param context: Request context :param image_id: The opaque image identifier :param user_id: Request user id :param project_id: Request project id :param target_path: Where the image data to write :raises NoImageHandlerAvailable: if no any image handler specified in the configuration is available for this request. """ handled = False if target_path is not None: target_path = target_path.strip() # Check if target image has been handled before, # we can using previous handler process it again directly. if target_path and _IMAGE_HANDLERS_ASSO: ret = _IMAGE_HANDLERS_ASSO.get(target_path) if ret: (image_handler, location, image_meta) = ret yield image_handler, location, image_meta handled = image_handler.last_ops_handled() image_meta = None if not handled and _IMAGE_HANDLERS: if context and image_id: (image_service, _image_id) = glance.get_remote_image_service( context, image_id) image_meta = image_service.show(context, image_id) # Note(zhiyan): Glance maybe can not receive image # location property since Glance disabled it by default. img_locs = image_service.get_locations(context, image_id) for image_handler in _IMAGE_HANDLERS: matched_locs = _match_locations(img_locs, image_handler.get_schemes()) for loc in matched_locs: yield image_handler, loc, image_meta handled = image_handler.last_ops_handled() if handled: return if not handled: # Note(zhiyan): using location-independent handler do it. for image_handler in _IMAGE_HANDLERS: if len(image_handler.get_schemes()) == 0: yield image_handler, None, image_meta handled = image_handler.last_ops_handled() if handled: return if not handled: LOG.error(_("Can not handle image: %(image_id)s %(target_path)s"), {'image_id': image_id, 'target_path': target_path}) raise exception.NoImageHandlerAvailable(image_id=image_id)
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