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OpenStack Study: prefetcher.py**** CubicPower OpenStack Study ****
# Copyright 2011 OpenStack Foundation # All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. """ Prefetches images into the Image Cache """ import eventlet from glance.common import exception from glance import context from glance.image_cache import base import glance.openstack.common.log as logging import glance.registry.client.v1.api as registry import glance.store LOG = logging.getLogger(__name__)
**** CubicPower OpenStack Study **** class Prefetcher(base.CacheApp):
**** CubicPower OpenStack Study **** def __init__(self): super(Prefetcher, self).__init__() registry.configure_registry_client() registry.configure_registry_admin_creds()
**** CubicPower OpenStack Study **** def fetch_image_into_cache(self, image_id): ctx = context.RequestContext(is_admin=True, show_deleted=True) try: image_meta = registry.get_image_metadata(ctx, image_id) if image_meta['status'] != 'active': LOG.warn(_("Image '%s' is not active. Not caching."), image_id) return False except exception.NotFound: LOG.warn(_("No metadata found for image '%s'"), image_id) return False location = image_meta['location'] image_data, image_size = glance.store.get_from_backend(ctx, location) LOG.debug(_("Caching image '%s'"), image_id) cache_tee_iter = self.cache.cache_tee_iter(image_id, image_data, image_meta['checksum']) # Image is tee'd into cache and checksum verified # as we iterate list(cache_tee_iter) return True
**** CubicPower OpenStack Study **** def run(self): images = self.cache.get_queued_images() if not images: LOG.debug(_("Nothing to prefetch.")) return True num_images = len(images) LOG.debug(_("Found %d images to prefetch"), num_images) pool = eventlet.GreenPool(num_images) results = pool.imap(self.fetch_image_into_cache, images) successes = sum([1 for r in results if r is True]) if successes != num_images: LOG.error(_("Failed to successfully cache all " "images in queue.")) return False LOG.info(_("Successfully cached all %d images"), num_images) return True
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