/usr/share/pyshared/glance/image_cache/__init__.py is in python-glance 2012.1.3+stable~20120821-120fcf-0ubuntu1.5.
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# 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.
"""
LRU Cache for Image Data
"""
import logging
from glance.common import cfg
from glance.common import exception
from glance.common import utils
logger = logging.getLogger(__name__)
DEFAULT_MAX_CACHE_SIZE = 10 * 1024 * 1024 * 1024 # 10 GB
class ImageCache(object):
"""Provides an LRU cache for image data."""
opts = [
cfg.StrOpt('image_cache_driver', default='sqlite'),
cfg.IntOpt('image_cache_max_size', default=10 * (1024 ** 3)), # 10 GB
cfg.IntOpt('image_cache_stall_time', default=86400), # 24 hours
cfg.StrOpt('image_cache_dir'),
]
def __init__(self, conf):
self.conf = conf
self.conf.register_opts(self.opts)
self.init_driver()
def init_driver(self):
"""
Create the driver for the cache
"""
driver_name = self.conf.image_cache_driver
driver_module = (__name__ + '.drivers.' + driver_name + '.Driver')
try:
self.driver_class = utils.import_class(driver_module)
logger.info(_("Image cache loaded driver '%s'.") %
driver_name)
except exception.ImportFailure, import_err:
logger.warn(_("Image cache driver "
"'%(driver_name)s' failed to load. "
"Got error: '%(import_err)s.") % locals())
driver_module = __name__ + '.drivers.sqlite.Driver'
logger.info(_("Defaulting to SQLite driver."))
self.driver_class = utils.import_class(driver_module)
self.configure_driver()
def configure_driver(self):
"""
Configure the driver for the cache and, if it fails to configure,
fall back to using the SQLite driver which has no odd dependencies
"""
try:
self.driver = self.driver_class(self.conf)
self.driver.configure()
except exception.BadDriverConfiguration, config_err:
driver_module = self.driver_class.__module__
logger.warn(_("Image cache driver "
"'%(driver_module)s' failed to configure. "
"Got error: '%(config_err)s") % locals())
logger.info(_("Defaulting to SQLite driver."))
default_module = __name__ + '.drivers.sqlite.Driver'
self.driver_class = utils.import_class(default_module)
self.driver = self.driver_class(self.conf)
self.driver.configure()
def is_cached(self, image_id):
"""
Returns True if the image with the supplied ID has its image
file cached.
:param image_id: Image ID
"""
return self.driver.is_cached(image_id)
def is_queued(self, image_id):
"""
Returns True if the image identifier is in our cache queue.
:param image_id: Image ID
"""
return self.driver.is_queued(image_id)
def get_cache_size(self):
"""
Returns the total size in bytes of the image cache.
"""
return self.driver.get_cache_size()
def get_hit_count(self, image_id):
"""
Return the number of hits that an image has
:param image_id: Opaque image identifier
"""
return self.driver.get_hit_count(image_id)
def get_cached_images(self):
"""
Returns a list of records about cached images.
"""
return self.driver.get_cached_images()
def delete_all_cached_images(self):
"""
Removes all cached image files and any attributes about the images
and returns the number of cached image files that were deleted.
"""
return self.driver.delete_all_cached_images()
def delete_cached_image(self, image_id):
"""
Removes a specific cached image file and any attributes about the image
:param image_id: Image ID
"""
self.driver.delete_cached_image(image_id)
def delete_all_queued_images(self):
"""
Removes all queued image files and any attributes about the images
and returns the number of queued image files that were deleted.
"""
return self.driver.delete_all_queued_images()
def delete_queued_image(self, image_id):
"""
Removes a specific queued image file and any attributes about the image
:param image_id: Image ID
"""
self.driver.delete_queued_image(image_id)
def prune(self):
"""
Removes all cached image files above the cache's maximum
size. Returns a tuple containing the total number of cached
files removed and the total size of all pruned image files.
"""
max_size = self.conf.image_cache_max_size
current_size = self.driver.get_cache_size()
if max_size > current_size:
logger.debug(_("Image cache has free space, skipping prune..."))
return (0, 0)
overage = current_size - max_size
logger.debug(_("Image cache currently %(overage)d bytes over max "
"size. Starting prune to max size of %(max_size)d ") %
locals())
total_bytes_pruned = 0
total_files_pruned = 0
entry = self.driver.get_least_recently_accessed()
while entry and current_size > max_size:
image_id, size = entry
logger.debug(_("Pruning '%(image_id)s' to free %(size)d bytes"),
{'image_id': image_id, 'size': size})
self.driver.delete_cached_image(image_id)
total_bytes_pruned = total_bytes_pruned + size
total_files_pruned = total_files_pruned + 1
current_size = current_size - size
entry = self.driver.get_least_recently_accessed()
logger.debug(_("Pruning finished pruning. "
"Pruned %(total_files_pruned)d and "
"%(total_bytes_pruned)d.") % locals())
return total_files_pruned, total_bytes_pruned
def clean(self, stall_time=None):
"""
Cleans up any invalid or incomplete cached images. The cache driver
decides what that means...
"""
self.driver.clean(stall_time)
def queue_image(self, image_id):
"""
This adds a image to be cache to the queue.
If the image already exists in the queue or has already been
cached, we return False, True otherwise
:param image_id: Image ID
"""
return self.driver.queue_image(image_id)
def get_caching_iter(self, image_id, image_iter):
"""
Returns an iterator that caches the contents of an image
while the image contents are read through the supplied
iterator.
:param image_id: Image ID
:param image_iter: Iterator that will read image contents
"""
if not self.driver.is_cacheable(image_id):
return image_iter
logger.debug(_("Tee'ing image '%s' into cache"), image_id)
def tee_iter(image_id):
try:
with self.driver.open_for_write(image_id) as cache_file:
for chunk in image_iter:
try:
cache_file.write(chunk)
finally:
yield chunk
cache_file.flush()
except Exception:
logger.exception(_("Exception encountered while tee'ing "
"image '%s' into cache. Continuing "
"with response.") % image_id)
# NOTE(markwash): continue responding even if caching failed
for chunk in image_iter:
yield chunk
return tee_iter(image_id)
def cache_image_iter(self, image_id, image_iter):
"""
Cache an image with supplied iterator.
:param image_id: Image ID
:param image_file: Iterator retrieving image chunks
:retval True if image file was cached, False otherwise
"""
if not self.driver.is_cacheable(image_id):
return False
with self.driver.open_for_write(image_id) as cache_file:
for chunk in image_iter:
cache_file.write(chunk)
cache_file.flush()
return True
def cache_image_file(self, image_id, image_file):
"""
Cache an image file.
:param image_id: Image ID
:param image_file: Image file to cache
:retval True if image file was cached, False otherwise
"""
CHUNKSIZE = 64 * 1024 * 1024
return self.cache_image_iter(image_id,
utils.chunkiter(image_file, CHUNKSIZE))
def open_for_read(self, image_id):
"""
Open and yield file for reading the image file for an image
with supplied identifier.
:note Upon successful reading of the image file, the image's
hit count will be incremented.
:param image_id: Image ID
"""
return self.driver.open_for_read(image_id)
def get_image_size(self, image_id):
"""
Return the size of the image file for an image with supplied
identifier.
:param image_id: Image ID
"""
return self.driver.get_image_size(image_id)
def get_queued_images(self):
"""
Returns a list of image IDs that are in the queue. The
list should be sorted by the time the image ID was inserted
into the queue.
"""
return self.driver.get_queued_images()
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