/usr/share/pyshared/glance/image_cache/drivers/sqlite.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.
"""
Cache driver that uses SQLite to store information about cached images
"""
from __future__ import absolute_import
from contextlib import contextmanager
import logging
import os
import stat
import time
from eventlet import sleep, timeout
import sqlite3
from glance.common import cfg
from glance.common import exception
from glance.image_cache.drivers import base
logger = logging.getLogger(__name__)
DEFAULT_SQL_CALL_TIMEOUT = 2
class SqliteConnection(sqlite3.Connection):
"""
SQLite DB Connection handler that plays well with eventlet,
slightly modified from Swift's similar code.
"""
def __init__(self, *args, **kwargs):
self.timeout_seconds = kwargs.get('timeout', DEFAULT_SQL_CALL_TIMEOUT)
kwargs['timeout'] = 0
sqlite3.Connection.__init__(self, *args, **kwargs)
def _timeout(self, call):
with timeout.Timeout(self.timeout_seconds):
while True:
try:
return call()
except sqlite3.OperationalError, e:
if 'locked' not in str(e):
raise
sleep(0.05)
def execute(self, *args, **kwargs):
return self._timeout(lambda: sqlite3.Connection.execute(
self, *args, **kwargs))
def commit(self):
return self._timeout(lambda: sqlite3.Connection.commit(self))
def dict_factory(cur, row):
return dict(
((col[0], row[idx]) for idx, col in enumerate(cur.description)))
class Driver(base.Driver):
"""
Cache driver that uses xattr file tags and requires a filesystem
that has atimes set.
"""
opts = [
cfg.StrOpt('image_cache_sqlite_db', default='cache.db'),
]
def configure(self):
"""
Configure the driver to use the stored configuration options
Any store that needs special configuration should implement
this method. If the store was not able to successfully configure
itself, it should raise `exception.BadDriverConfiguration`
"""
super(Driver, self).configure()
self.conf.register_opts(self.opts)
# Create the SQLite database that will hold our cache attributes
self.initialize_db()
def initialize_db(self):
db = self.conf.image_cache_sqlite_db
self.db_path = os.path.join(self.base_dir, db)
try:
conn = sqlite3.connect(self.db_path, check_same_thread=False,
factory=SqliteConnection)
conn.executescript("""
CREATE TABLE IF NOT EXISTS cached_images (
image_id TEXT PRIMARY KEY,
last_accessed REAL DEFAULT 0.0,
last_modified REAL DEFAULT 0.0,
size INTEGER DEFAULT 0,
hits INTEGER DEFAULT 0,
checksum TEXT
);
""")
conn.close()
except sqlite3.DatabaseError, e:
msg = _("Failed to initialize the image cache database. "
"Got error: %s") % e
logger.error(msg)
raise exception.BadDriverConfiguration(driver_name='sqlite',
reason=msg)
def get_cache_size(self):
"""
Returns the total size in bytes of the image cache.
"""
sizes = []
for path in self.get_cache_files(self.base_dir):
if path == self.db_path:
continue
file_info = os.stat(path)
sizes.append(file_info[stat.ST_SIZE])
return sum(sizes)
def get_hit_count(self, image_id):
"""
Return the number of hits that an image has.
:param image_id: Opaque image identifier
"""
if not self.is_cached(image_id):
return 0
hits = 0
with self.get_db() as db:
cur = db.execute("""SELECT hits FROM cached_images
WHERE image_id = ?""",
(image_id,))
hits = cur.fetchone()[0]
return hits
def get_cached_images(self):
"""
Returns a list of records about cached images.
"""
logger.debug(_("Gathering cached image entries."))
with self.get_db() as db:
cur = db.execute("""SELECT
image_id, hits, last_accessed, last_modified, size
FROM cached_images
ORDER BY image_id""")
cur.row_factory = dict_factory
return [r for r in cur]
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 os.path.exists(self.get_image_filepath(image_id))
def is_cacheable(self, image_id):
"""
Returns True if the image with the supplied ID can have its
image file cached, False otherwise.
:param image_id: Image ID
"""
# Make sure we're not already cached or caching the image
return not (self.is_cached(image_id) or
self.is_being_cached(image_id))
def is_being_cached(self, image_id):
"""
Returns True if the image with supplied id is currently
in the process of having its image file cached.
:param image_id: Image ID
"""
path = self.get_image_filepath(image_id, 'incomplete')
return os.path.exists(path)
def is_queued(self, image_id):
"""
Returns True if the image identifier is in our cache queue.
:param image_id: Image ID
"""
path = self.get_image_filepath(image_id, 'queue')
return os.path.exists(path)
def delete_all_cached_images(self):
"""
Removes all cached image files and any attributes about the images
"""
deleted = 0
with self.get_db() as db:
for path in self.get_cache_files(self.base_dir):
delete_cached_file(path)
deleted += 1
db.execute("""DELETE FROM cached_images""")
db.commit()
return deleted
def delete_cached_image(self, image_id):
"""
Removes a specific cached image file and any attributes about the image
:param image_id: Image ID
"""
path = self.get_image_filepath(image_id)
with self.get_db() as db:
delete_cached_file(path)
db.execute("""DELETE FROM cached_images WHERE image_id = ?""",
(image_id, ))
db.commit()
def delete_all_queued_images(self):
"""
Removes all queued image files and any attributes about the images
"""
files = [f for f in self.get_cache_files(self.queue_dir)]
for file in files:
os.unlink(file)
return len(files)
def delete_queued_image(self, image_id):
"""
Removes a specific queued image file and any attributes about the image
:param image_id: Image ID
"""
path = self.get_image_filepath(image_id, 'queue')
if os.path.exists(path):
os.unlink(path)
def clean(self, stall_time=None):
"""
Delete any image files in the invalid directory and any
files in the incomplete directory that are older than a
configurable amount of time.
"""
self.delete_invalid_files()
if stall_time is None:
stall_time = self.conf.image_cache_stall_time
now = time.time()
older_than = now - stall_time
self.delete_stalled_files(older_than)
def get_least_recently_accessed(self):
"""
Return a tuple containing the image_id and size of the least recently
accessed cached file, or None if no cached files.
"""
with self.get_db() as db:
cur = db.execute("""SELECT image_id FROM cached_images
ORDER BY last_accessed LIMIT 1""")
image_id = cur.fetchone()[0]
path = self.get_image_filepath(image_id)
file_info = os.stat(path)
return image_id, file_info[stat.ST_SIZE]
@contextmanager
def open_for_write(self, image_id):
"""
Open a file for writing the image file for an image
with supplied identifier.
:param image_id: Image ID
"""
incomplete_path = self.get_image_filepath(image_id, 'incomplete')
def commit():
with self.get_db() as db:
final_path = self.get_image_filepath(image_id)
logger.debug(_("Fetch finished, moving "
"'%(incomplete_path)s' to '%(final_path)s'"),
dict(incomplete_path=incomplete_path,
final_path=final_path))
os.rename(incomplete_path, final_path)
# Make sure that we "pop" the image from the queue...
if self.is_queued(image_id):
os.unlink(self.get_image_filepath(image_id, 'queue'))
filesize = os.path.getsize(final_path)
now = time.time()
db.execute("""INSERT INTO cached_images
(image_id, last_accessed, last_modified, hits, size)
VALUES (?, 0, ?, 0, ?)""",
(image_id, now, filesize))
db.commit()
def rollback(e):
with self.get_db() as db:
if os.path.exists(incomplete_path):
invalid_path = self.get_image_filepath(image_id, 'invalid')
logger.debug(_("Fetch of cache file failed, rolling back "
"by moving '%(incomplete_path)s' to "
"'%(invalid_path)s'") % locals())
os.rename(incomplete_path, invalid_path)
db.execute("""DELETE FROM cached_images
WHERE image_id = ?""", (image_id, ))
db.commit()
try:
with open(incomplete_path, 'wb') as cache_file:
yield cache_file
except Exception as e:
rollback(e)
raise
else:
commit()
@contextmanager
def open_for_read(self, image_id):
"""
Open and yield file for reading the image file for an image
with supplied identifier.
:param image_id: Image ID
"""
path = self.get_image_filepath(image_id)
with open(path, 'rb') as cache_file:
yield cache_file
now = time.time()
with self.get_db() as db:
db.execute("""UPDATE cached_images
SET hits = hits + 1, last_accessed = ?
WHERE image_id = ?""",
(now, image_id))
db.commit()
@contextmanager
def get_db(self):
"""
Returns a context manager that produces a database connection that
self-closes and calls rollback if an error occurs while using the
database connection
"""
conn = sqlite3.connect(self.db_path, check_same_thread=False,
factory=SqliteConnection)
conn.row_factory = sqlite3.Row
conn.text_factory = str
conn.execute('PRAGMA synchronous = NORMAL')
conn.execute('PRAGMA count_changes = OFF')
conn.execute('PRAGMA temp_store = MEMORY')
try:
yield conn
except sqlite3.DatabaseError, e:
msg = _("Error executing SQLite call. Got error: %s") % e
logger.error(msg)
conn.rollback()
finally:
conn.close()
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
"""
if self.is_cached(image_id):
msg = _("Not queueing image '%s'. Already cached.") % image_id
logger.warn(msg)
return False
if self.is_being_cached(image_id):
msg = _("Not queueing image '%s'. Already being "
"written to cache") % image_id
logger.warn(msg)
return False
if self.is_queued(image_id):
msg = _("Not queueing image '%s'. Already queued.") % image_id
logger.warn(msg)
return False
path = self.get_image_filepath(image_id, 'queue')
# Touch the file to add it to the queue
with open(path, "w") as f:
pass
return True
def delete_invalid_files(self):
"""
Removes any invalid cache entries
"""
for path in self.get_cache_files(self.invalid_dir):
os.unlink(path)
logger.info("Removed invalid cache file %s", path)
def delete_stalled_files(self, older_than):
"""
Removes any incomplete cache entries older than a
supplied modified time.
:param older_than: Files written to on or before this timestemp
will be deleted.
"""
for path in self.get_cache_files(self.incomplete_dir):
os.unlink(path)
logger.info("Removed stalled cache file %s", path)
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.
"""
files = [f for f in self.get_cache_files(self.queue_dir)]
items = []
for path in files:
mtime = os.path.getmtime(path)
items.append((mtime, os.path.basename(path)))
items.sort()
return [image_id for (mtime, image_id) in items]
def get_cache_files(self, basepath):
"""
Returns cache files in the supplied directory
:param basepath: Directory to look in for cache files
"""
for fname in os.listdir(basepath):
path = os.path.join(basepath, fname)
if path != self.db_path and os.path.isfile(path):
yield path
def delete_cached_file(path):
if os.path.exists(path):
logger.debug(_("Deleting image cache file '%s'"), path)
os.unlink(path)
else:
logger.warn(_("Cached image file '%s' doesn't exist, unable to"
" delete"), path)
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