class Prefetcher(object): def __init__(self, options): self.options = options glance.store.create_stores(options) self.cache = ImageCache(options) def fetch_image_into_cache(self, image_id): ctx = context.RequestContext(is_admin=True, show_deleted=True) image_meta = registry.get_image_metadata( self.options, ctx, image_id) with self.cache.open(image_meta, "wb") as cache_file: chunks = get_from_backend(image_meta['location'], expected_size=image_meta['size'], options=self.options) for chunk in chunks: cache_file.write(chunk) def run(self): if self.cache.is_currently_prefetching_any_images(): logger.debug(_("Currently prefetching, going back to sleep...")) return try: image_id = self.cache.pop_prefetch_item() except IndexError: logger.debug(_("Nothing to prefetch, going back to sleep...")) return if self.cache.hit(image_id): logger.warn(_("Image %s is already in the cache, deleting " "prefetch job and going back to sleep..."), image_id) self.cache.delete_queued_prefetch_image(image_id) return # NOTE(sirp): if someone is already downloading an image that is in # the prefetch queue, then go ahead and delete that item and try to # prefetch another if self.cache.is_image_currently_being_written(image_id): logger.warn(_("Image %s is already being cached, deleting " "prefetch job and going back to sleep..."), image_id) self.cache.delete_queued_prefetch_image(image_id) return logger.debug(_("Prefetching '%s'"), image_id) self.cache.do_prefetch(image_id) try: self.fetch_image_into_cache(image_id) finally: self.cache.delete_prefetching_image(image_id)