prefetcher.py

# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2011 OpenStack LLC.
# 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 logging

import eventlet

from glance.common import config
from glance.common import context
from glance.common import exception
from glance.image_cache import ImageCache
from glance import registry
from glance.store import get_from_backend


logger = logging.getLogger(__name__)


class Prefetcher(object):

    def __init__(self, options):
        self.options = options
        self.cache = ImageCache(options)
        registry.configure_registry_client(options)

    def fetch_image_into_cache(self, image_id):
        auth_tok = self.options.get('admin_token')
        ctx = context.RequestContext(is_admin=True, show_deleted=True,
                                     auth_tok=auth_tok)
        try:
            image_meta = registry.get_image_metadata(ctx, image_id)
            if image_meta['status'] != 'active':
                logger.warn(_("Image '%s' is not active. Not caching."),
                            image_id)
                return False

        except exception.NotFound:
            logger.warn(_("No metadata found for image '%s'"), image_id)
            return False

        chunks = get_from_backend(image_meta['location'],
                                  options=self.options)
        logger.debug(_("Caching image '%s'"), image_id)
        self.cache.cache_image_iter(image_id, chunks)
        return True

    def run(self):

        images = self.cache.get_cache_queue()
        if not images:
            logger.debug(_("Nothing to prefetch."))
            return True

        num_images = len(images)
        logger.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:
            logger.error(_("Failed to successfully cache all "
                           "images in queue."))
            return False

        logger.info(_("Successfully cached all %d images"), num_images)
        return True


def app_factory(global_config, **local_conf):
    conf = global_config.copy()
    conf.update(local_conf)
    return Prefetcher(conf)