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)
