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"""Core disk and file backed cache API.
"""
import codecs
import contextlib as cl
import errno
import functools as ft
import io
import json
import os
import os.path as op
import pickletools
import sqlite3
import struct
import sys
import tempfile
import threading
import time
import warnings
import zlib
############################################################################
# BEGIN Python 2/3 Shims
############################################################################
if sys.hexversion < 0x03000000:
import cPickle as pickle # pylint: disable=import-error
from cStringIO import StringIO as BytesIO # pylint: disable=import-error
from thread import get_ident # pylint: disable=import-error,no-name-in-module
TextType = unicode # pylint: disable=invalid-name,undefined-variable
BytesType = str
INT_TYPES = int, long # pylint: disable=undefined-variable
range = xrange # pylint: disable=redefined-builtin,invalid-name,undefined-variable
io_open = io.open # pylint: disable=invalid-name
else:
import pickle
from io import BytesIO # pylint: disable=ungrouped-imports
from threading import get_ident
TextType = str
BytesType = bytes
INT_TYPES = (int,)
io_open = open # pylint: disable=invalid-name
def full_name(func):
"Return full name of `func` by adding the module and function name."
try:
# The __qualname__ attribute is only available in Python 3.3 and later.
# GrantJ 2019-03-29 Remove after support for Python 2 is dropped.
name = func.__qualname__
except AttributeError:
name = func.__name__
return func.__module__ + '.' + name
############################################################################
# END Python 2/3 Shims
############################################################################
try:
WindowsError
except NameError:
class WindowsError(Exception):
"Windows error place-holder on platforms without support."
class Constant(tuple):
"Pretty display of immutable constant."
def __new__(cls, name):
return tuple.__new__(cls, (name,))
def __repr__(self):
return '%s' % self[0]
DBNAME = 'cache.db'
ENOVAL = Constant('ENOVAL')
UNKNOWN = Constant('UNKNOWN')
MODE_NONE = 0
MODE_RAW = 1
MODE_BINARY = 2
MODE_TEXT = 3
MODE_PICKLE = 4
DEFAULT_SETTINGS = {
u'statistics': 0, # False
u'tag_index': 0, # False
u'eviction_policy': u'least-recently-stored',
u'size_limit': 2 ** 30, # 1gb
u'cull_limit': 10,
u'sqlite_auto_vacuum': 1, # FULL
u'sqlite_cache_size': 2 ** 13, # 8,192 pages
u'sqlite_journal_mode': u'wal',
u'sqlite_mmap_size': 2 ** 26, # 64mb
u'sqlite_synchronous': 1, # NORMAL
u'disk_min_file_size': 2 ** 15, # 32kb
u'disk_pickle_protocol': pickle.HIGHEST_PROTOCOL,
}
METADATA = {
u'count': 0,
u'size': 0,
u'hits': 0,
u'misses': 0,
}
EVICTION_POLICY = {
'none': {
'init': None,
'get': None,
'cull': None,
},
'least-recently-stored': {
'init': (
'CREATE INDEX IF NOT EXISTS Cache_store_time ON'
' Cache (store_time)'
),
'get': None,
'cull': 'SELECT {fields} FROM Cache ORDER BY store_time LIMIT ?',
},
'least-recently-used': {
'init': (
'CREATE INDEX IF NOT EXISTS Cache_access_time ON'
' Cache (access_time)'
),
'get': 'access_time = {now}',
'cull': 'SELECT {fields} FROM Cache ORDER BY access_time LIMIT ?',
},
'least-frequently-used': {
'init': (
'CREATE INDEX IF NOT EXISTS Cache_access_count ON'
' Cache (access_count)'
),
'get': 'access_count = access_count + 1',
'cull': 'SELECT {fields} FROM Cache ORDER BY access_count LIMIT ?',
},
}
class Disk(object):
"Cache key and value serialization for SQLite database and files."
def __init__(self, directory, min_file_size=0, pickle_protocol=0):
"""Initialize disk instance.
:param str directory: directory path
:param int min_file_size: minimum size for file use
:param int pickle_protocol: pickle protocol for serialization
"""
self._directory = directory
self.min_file_size = min_file_size
self.pickle_protocol = pickle_protocol
def hash(self, key):
"""Compute portable hash for `key`.
:param key: key to hash
:return: hash value
"""
mask = 0xFFFFFFFF
disk_key, _ = self.put(key)
type_disk_key = type(disk_key)
if type_disk_key is sqlite3.Binary:
return zlib.adler32(disk_key) & mask
elif type_disk_key is TextType:
return zlib.adler32(disk_key.encode('utf-8')) & mask # pylint: disable=no-member
elif type_disk_key in INT_TYPES:
return disk_key % mask
else:
assert type_disk_key is float
return zlib.adler32(struct.pack('!d', disk_key)) & mask
def put(self, key):
"""Convert `key` to fields key and raw for Cache table.
:param key: key to convert
:return: (database key, raw boolean) pair
"""
# pylint: disable=bad-continuation,unidiomatic-typecheck
type_key = type(key)
if type_key is BytesType:
return sqlite3.Binary(key), True
elif ((type_key is TextType)
or (type_key in INT_TYPES
and -9223372036854775808 <= key <= 9223372036854775807)
or (type_key is float)):
return key, True
else:
data = pickle.dumps(key, protocol=self.pickle_protocol)
result = pickletools.optimize(data)
return sqlite3.Binary(result), False
def get(self, key, raw):
"""Convert fields `key` and `raw` from Cache table to key.
:param key: database key to convert
:param bool raw: flag indicating raw database storage
:return: corresponding Python key
"""
# pylint: disable=no-self-use,unidiomatic-typecheck
if raw:
return BytesType(key) if type(key) is sqlite3.Binary else key
else:
return pickle.load(BytesIO(key))
def store(self, value, read, key=UNKNOWN):
"""Convert `value` to fields size, mode, filename, and value for Cache
table.
:param value: value to convert
:param bool read: True when value is file-like object
:param key: key for item (default UNKNOWN)
:return: (size, mode, filename, value) tuple for Cache table
"""
# pylint: disable=unidiomatic-typecheck
type_value = type(value)
min_file_size = self.min_file_size
if ((type_value is TextType and len(value) < min_file_size)
or (type_value in INT_TYPES
and -9223372036854775808 <= value <= 9223372036854775807)
or (type_value is float)):
return 0, MODE_RAW, None, value
elif type_value is BytesType:
if len(value) < min_file_size:
return 0, MODE_RAW, None, sqlite3.Binary(value)
else:
filename, full_path = self.filename(key, value)
with open(full_path, 'wb') as writer:
writer.write(value)
return len(value), MODE_BINARY, filename, None
elif type_value is TextType:
filename, full_path = self.filename(key, value)
with io_open(full_path, 'w', encoding='UTF-8') as writer:
writer.write(value)
size = op.getsize(full_path)
return size, MODE_TEXT, filename, None
elif read:
size = 0
reader = ft.partial(value.read, 2 ** 22)
filename, full_path = self.filename(key, value)
with open(full_path, 'wb') as writer:
for chunk in iter(reader, b''):
size += len(chunk)
writer.write(chunk)
return size, MODE_BINARY, filename, None
else:
result = pickle.dumps(value, protocol=self.pickle_protocol)
if len(result) < min_file_size:
return 0, MODE_PICKLE, None, sqlite3.Binary(result)
else:
filename, full_path = self.filename(key, value)
with open(full_path, 'wb') as writer:
writer.write(result)
return len(result), MODE_PICKLE, filename, None
def fetch(self, mode, filename, value, read):
"""Convert fields `mode`, `filename`, and `value` from Cache table to
value.
:param int mode: value mode raw, binary, text, or pickle
:param str filename: filename of corresponding value
:param value: database value
:param bool read: when True, return an open file handle
:return: corresponding Python value
"""
# pylint: disable=no-self-use,unidiomatic-typecheck
if mode == MODE_RAW:
return BytesType(value) if type(value) is sqlite3.Binary else value
elif mode == MODE_BINARY:
if read:
return open(op.join(self._directory, filename), 'rb')
else:
with open(op.join(self._directory, filename), 'rb') as reader:
return reader.read()
elif mode == MODE_TEXT:
full_path = op.join(self._directory, filename)
with io_open(full_path, 'r', encoding='UTF-8') as reader:
return reader.read()
elif mode == MODE_PICKLE:
if value is None:
with open(op.join(self._directory, filename), 'rb') as reader:
return pickle.load(reader)
else:
return pickle.load(BytesIO(value))
def filename(self, key=UNKNOWN, value=UNKNOWN):
"""Return filename and full-path tuple for file storage.
Filename will be a randomly generated 28 character hexadecimal string
with ".val" suffixed. Two levels of sub-directories will be used to
reduce the size of directories. On older filesystems, lookups in
directories with many files may be slow.
The default implementation ignores the `key` and `value` parameters.
In some scenarios, for example :meth:`Cache.push
<diskcache.Cache.push>`, the `key` or `value` may not be known when the
item is stored in the cache.
:param key: key for item (default UNKNOWN)
:param value: value for item (default UNKNOWN)
"""
# pylint: disable=unused-argument
hex_name = codecs.encode(os.urandom(16), 'hex').decode('utf-8')
sub_dir = op.join(hex_name[:2], hex_name[2:4])
name = hex_name[4:] + '.val'
directory = op.join(self._directory, sub_dir)
try:
os.makedirs(directory)
except OSError as error:
if error.errno != errno.EEXIST:
raise
filename = op.join(sub_dir, name)
full_path = op.join(self._directory, filename)
return filename, full_path
def remove(self, filename):
"""Remove a file given by `filename`.
This method is cross-thread and cross-process safe. If an "error no
entry" occurs, it is suppressed.
:param str filename: relative path to file
"""
full_path = op.join(self._directory, filename)
try:
os.remove(full_path)
except WindowsError:
pass
except OSError as error:
if error.errno != errno.ENOENT:
# ENOENT may occur if two caches attempt to delete the same
# file at the same time.
raise
class JSONDisk(Disk):
"Cache key and value using JSON serialization with zlib compression."
def __init__(self, directory, compress_level=1, **kwargs):
"""Initialize JSON disk instance.
Keys and values are compressed using the zlib library. The
`compress_level` is an integer from 0 to 9 controlling the level of
compression; 1 is fastest and produces the least compression, 9 is
slowest and produces the most compression, and 0 is no compression.
:param str directory: directory path
:param int compress_level: zlib compression level (default 1)
:param kwargs: super class arguments
"""
self.compress_level = compress_level
super(JSONDisk, self).__init__(directory, **kwargs)
def put(self, key):
json_bytes = json.dumps(key).encode('utf-8')
data = zlib.compress(json_bytes, self.compress_level)
return super(JSONDisk, self).put(data)
def get(self, key, raw):
data = super(JSONDisk, self).get(key, raw)
return json.loads(zlib.decompress(data).decode('utf-8'))
def store(self, value, read, key=UNKNOWN):
if not read:
json_bytes = json.dumps(value).encode('utf-8')
value = zlib.compress(json_bytes, self.compress_level)
return super(JSONDisk, self).store(value, read, key=key)
def fetch(self, mode, filename, value, read):
data = super(JSONDisk, self).fetch(mode, filename, value, read)
if not read:
data = json.loads(zlib.decompress(data).decode('utf-8'))
return data
class Timeout(Exception):
"Database timeout expired."
class UnknownFileWarning(UserWarning):
"Warning used by Cache.check for unknown files."
class EmptyDirWarning(UserWarning):
"Warning used by Cache.check for empty directories."
def args_to_key(base, args, kwargs, typed):
"""Create cache key out of function arguments.
:param tuple base: base of key
:param tuple args: function arguments
:param dict kwargs: function keyword arguments
:param bool typed: include types in cache key
:return: cache key tuple
"""
key = base + args
if kwargs:
key += (ENOVAL,)
sorted_items = sorted(kwargs.items())
for item in sorted_items:
key += item
if typed:
key += tuple(type(arg) for arg in args)
if kwargs:
key += tuple(type(value) for _, value in sorted_items)
return key
class Cache(object):
"Disk and file backed cache."
# pylint: disable=bad-continuation
def __init__(self, directory=None, timeout=60, disk=Disk, **settings):
"""Initialize cache instance.
:param str directory: cache directory
:param float timeout: SQLite connection timeout
:param disk: Disk type or subclass for serialization
:param settings: any of DEFAULT_SETTINGS
"""
try:
assert issubclass(disk, Disk)
except (TypeError, AssertionError):
raise ValueError('disk must subclass diskcache.Disk')
if directory is None:
directory = tempfile.mkdtemp(prefix='diskcache-')
directory = op.expanduser(directory)
directory = op.expandvars(directory)
self._directory = directory
self._timeout = 0 # Manually handle retries during initialization.
self._local = threading.local()
self._txn_id = None
if not op.isdir(directory):
try:
os.makedirs(directory, 0o755)
except OSError as error:
if error.errno != errno.EEXIST:
raise EnvironmentError(
error.errno,
'Cache directory "%s" does not exist'
' and could not be created' % self._directory
)
sql = self._sql_retry
# Setup Settings table.
try:
current_settings = dict(sql(
'SELECT key, value FROM Settings'
).fetchall())
except sqlite3.OperationalError:
current_settings = {}
sets = DEFAULT_SETTINGS.copy()
sets.update(current_settings)
sets.update(settings)
for key in METADATA:
sets.pop(key, None)
# Chance to set pragmas before any tables are created.
for key, value in sorted(sets.items()):
if key.startswith('sqlite_'):
self.reset(key, value, update=False)
sql('CREATE TABLE IF NOT EXISTS Settings ('
' key TEXT NOT NULL UNIQUE,'
' value)'
)
# Setup Disk object (must happen after settings initialized).
kwargs = {
key[5:]: value for key, value in sets.items()
if key.startswith('disk_')
}
self._disk = disk(directory, **kwargs)
# Set cached attributes: updates settings and sets pragmas.
for key, value in sets.items():
query = 'INSERT OR REPLACE INTO Settings VALUES (?, ?)'
sql(query, (key, value))
self.reset(key, value)
for key, value in METADATA.items():
query = 'INSERT OR IGNORE INTO Settings VALUES (?, ?)'
sql(query, (key, value))
self.reset(key)
(self._page_size,), = sql('PRAGMA page_size').fetchall()
# Setup Cache table.
sql('CREATE TABLE IF NOT EXISTS Cache ('
' rowid INTEGER PRIMARY KEY,'
' key BLOB,'
' raw INTEGER,'
' store_time REAL,'
' expire_time REAL,'
' access_time REAL,'
' access_count INTEGER DEFAULT 0,'
' tag BLOB,'
' size INTEGER DEFAULT 0,'
' mode INTEGER DEFAULT 0,'
' filename TEXT,'
' value BLOB)'
)
sql('CREATE UNIQUE INDEX IF NOT EXISTS Cache_key_raw ON'
' Cache(key, raw)'
)
sql('CREATE INDEX IF NOT EXISTS Cache_expire_time ON'
' Cache (expire_time)'
)
query = EVICTION_POLICY[self.eviction_policy]['init']
if query is not None:
sql(query)
# Use triggers to keep Metadata updated.
sql('CREATE TRIGGER IF NOT EXISTS Settings_count_insert'
' AFTER INSERT ON Cache FOR EACH ROW BEGIN'
' UPDATE Settings SET value = value + 1'
' WHERE key = "count"; END'
)
sql('CREATE TRIGGER IF NOT EXISTS Settings_count_delete'
' AFTER DELETE ON Cache FOR EACH ROW BEGIN'
' UPDATE Settings SET value = value - 1'
' WHERE key = "count"; END'
)
sql('CREATE TRIGGER IF NOT EXISTS Settings_size_insert'
' AFTER INSERT ON Cache FOR EACH ROW BEGIN'
' UPDATE Settings SET value = value + NEW.size'
' WHERE key = "size"; END'
)
sql('CREATE TRIGGER IF NOT EXISTS Settings_size_update'
' AFTER UPDATE ON Cache FOR EACH ROW BEGIN'
' UPDATE Settings'
' SET value = value + NEW.size - OLD.size'
' WHERE key = "size"; END'
)
sql('CREATE TRIGGER IF NOT EXISTS Settings_size_delete'
' AFTER DELETE ON Cache FOR EACH ROW BEGIN'
' UPDATE Settings SET value = value - OLD.size'
' WHERE key = "size"; END'
)
# Create tag index if requested.
if self.tag_index: # pylint: disable=no-member
self.create_tag_index()
else:
self.drop_tag_index()
# Close and re-open database connection with given timeout.
self.close()
self._timeout = timeout
self._sql # pylint: disable=pointless-statement
@property
def directory(self):
"""Cache directory."""
return self._directory
@property
def timeout(self):
"""SQLite connection timeout value in seconds."""
return self._timeout
@property
def disk(self):
"""Disk used for serialization."""
return self._disk
@property
def _con(self):
# Check process ID to support process forking. If the process
# ID changes, close the connection and update the process ID.
local_pid = getattr(self._local, 'pid', None)
pid = os.getpid()
if local_pid != pid:
self.close()
self._local.pid = pid
con = getattr(self._local, 'con', None)
if con is None:
con = self._local.con = sqlite3.connect(
op.join(self._directory, DBNAME),
timeout=self._timeout,
isolation_level=None,
)
# Some SQLite pragmas work on a per-connection basis so
# query the Settings table and reset the pragmas. The
# Settings table may not exist so catch and ignore the
# OperationalError that may occur.
try:
select = 'SELECT key, value FROM Settings'
settings = con.execute(select).fetchall()
except sqlite3.OperationalError:
pass
else:
for key, value in settings:
if key.startswith('sqlite_'):
self.reset(key, value, update=False)
return con
@property
def _sql(self):
return self._con.execute
@property
def _sql_retry(self):
sql = self._sql
# 2018-11-01 GrantJ - Some SQLite builds/versions handle
# the SQLITE_BUSY return value and connection parameter
# "timeout" differently. For a more reliable duration,
# manually retry the statement for 60 seconds. Only used
# by statements which modify the database and do not use
# a transaction (like those in ``__init__`` or ``reset``).
# See Issue #85 for and tests/issue_85.py for more details.
def _execute_with_retry(statement, *args, **kwargs):
start = time.time()
while True:
try:
return sql(statement, *args, **kwargs)
except sqlite3.OperationalError as exc:
if str(exc) != 'database is locked':
raise
diff = time.time() - start
if diff > 60:
raise
time.sleep(0.001)
return _execute_with_retry
@cl.contextmanager
def transact(self, retry=False):
"""Context manager to perform a transaction by locking the cache.
While the cache is locked, no other write operation is permitted.
Transactions should therefore be as short as possible. Read and write
operations performed in a transaction are atomic. Read operations may
occur concurrent to a transaction.
Transactions may be nested and may not be shared between threads.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
>>> cache = Cache()
>>> with cache.transact(): # Atomically increment two keys.
... _ = cache.incr('total', 123.4)
... _ = cache.incr('count', 1)
>>> with cache.transact(): # Atomically calculate average.
... average = cache['total'] / cache['count']
>>> average
123.4
:param bool retry: retry if database timeout occurs (default False)
:return: context manager for use in `with` statement
:raises Timeout: if database timeout occurs
"""
with self._transact(retry=retry):
yield
@cl.contextmanager
def _transact(self, retry=False, filename=None):
sql = self._sql
filenames = []
_disk_remove = self._disk.remove
tid = get_ident()
txn_id = self._txn_id
if tid == txn_id:
begin = False
else:
while True:
try:
sql('BEGIN IMMEDIATE')
begin = True
self._txn_id = tid
break
except sqlite3.OperationalError:
if retry:
continue
if filename is not None:
_disk_remove(filename)
raise Timeout
try:
yield sql, filenames.append
except BaseException:
if begin:
assert self._txn_id == tid
self._txn_id = None
sql('ROLLBACK')
raise
else:
if begin:
assert self._txn_id == tid
self._txn_id = None
sql('COMMIT')
for name in filenames:
if name is not None:
_disk_remove(name)
def set(self, key, value, expire=None, read=False, tag=None, retry=False):
"""Set `key` and `value` item in cache.
When `read` is `True`, `value` should be a file-like object opened
for reading in binary mode.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key for item
:param value: value for item
:param float expire: seconds until item expires
(default None, no expiry)
:param bool read: read value as bytes from file (default False)
:param str tag: text to associate with key (default None)
:param bool retry: retry if database timeout occurs (default False)
:return: True if item was set
:raises Timeout: if database timeout occurs
"""
now = time.time()
db_key, raw = self._disk.put(key)
expire_time = None if expire is None else now + expire
size, mode, filename, db_value = self._disk.store(value, read, key=key)
columns = (expire_time, tag, size, mode, filename, db_value)
# The order of SELECT, UPDATE, and INSERT is important below.
#
# Typical cache usage pattern is:
#
# value = cache.get(key)
# if value is None:
# value = expensive_calculation()
# cache.set(key, value)
#
# Cache.get does not evict expired keys to avoid writes during lookups.
# Commonly used/expired keys will therefore remain in the cache making
# an UPDATE the preferred path.
#
# The alternative is to assume the key is not present by first trying
# to INSERT and then handling the IntegrityError that occurs from
# violating the UNIQUE constraint. This optimistic approach was
# rejected based on the common cache usage pattern.
#
# INSERT OR REPLACE aka UPSERT is not used because the old filename may
# need cleanup.
with self._transact(retry, filename) as (sql, cleanup):
rows = sql(
'SELECT rowid, filename FROM Cache'
' WHERE key = ? AND raw = ?',
(db_key, raw),
).fetchall()
if rows:
(rowid, old_filename), = rows
cleanup(old_filename)
self._row_update(rowid, now, columns)
else:
self._row_insert(db_key, raw, now, columns)
self._cull(now, sql, cleanup)
return True
def __setitem__(self, key, value):
"""Set corresponding `value` for `key` in cache.
:param key: key for item
:param value: value for item
:return: corresponding value
:raises KeyError: if key is not found
"""
self.set(key, value, retry=True)
def _row_update(self, rowid, now, columns):
sql = self._sql
expire_time, tag, size, mode, filename, value = columns
sql('UPDATE Cache SET'
' store_time = ?,'
' expire_time = ?,'
' access_time = ?,'
' access_count = ?,'
' tag = ?,'
' size = ?,'
' mode = ?,'
' filename = ?,'
' value = ?'
' WHERE rowid = ?', (
now, # store_time
expire_time,
now, # access_time
0, # access_count
tag,
size,
mode,
filename,
value,
rowid,
),
)
def _row_insert(self, key, raw, now, columns):
sql = self._sql
expire_time, tag, size, mode, filename, value = columns
sql('INSERT INTO Cache('
' key, raw, store_time, expire_time, access_time,'
' access_count, tag, size, mode, filename, value'
') VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)', (
key,
raw,
now, # store_time
expire_time,
now, # access_time
0, # access_count
tag,
size,
mode,
filename,
value,
),
)
def _cull(self, now, sql, cleanup, limit=None):
cull_limit = self.cull_limit if limit is None else limit
if cull_limit == 0:
return
# Evict expired keys.
select_expired_template = (
'SELECT %s FROM Cache'
' WHERE expire_time IS NOT NULL AND expire_time < ?'
' ORDER BY expire_time LIMIT ?'
)
select_expired = select_expired_template % 'filename'
rows = sql(select_expired, (now, cull_limit)).fetchall()
if rows:
delete_expired = (
'DELETE FROM Cache WHERE rowid IN (%s)'
% (select_expired_template % 'rowid')
)
sql(delete_expired, (now, cull_limit))
for filename, in rows:
cleanup(filename)
cull_limit -= len(rows)
if cull_limit == 0:
return
# Evict keys by policy.
select_policy = EVICTION_POLICY[self.eviction_policy]['cull']
if select_policy is None or self.volume() < self.size_limit:
return
select_filename = select_policy.format(fields='filename', now=now)
rows = sql(select_filename, (cull_limit,)).fetchall()
if rows:
delete = (
'DELETE FROM Cache WHERE rowid IN (%s)'
% (select_policy.format(fields='rowid', now=now))
)
sql(delete, (cull_limit,))
for filename, in rows:
cleanup(filename)
def touch(self, key, expire=None, retry=False):
"""Touch `key` in cache and update `expire` time.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key for item
:param float expire: seconds until item expires
(default None, no expiry)
:param bool retry: retry if database timeout occurs (default False)
:return: True if key was touched
:raises Timeout: if database timeout occurs
"""
now = time.time()
db_key, raw = self._disk.put(key)
expire_time = None if expire is None else now + expire
with self._transact(retry) as (sql, _):
rows = sql(
'SELECT rowid, expire_time FROM Cache'
' WHERE key = ? AND raw = ?',
(db_key, raw),
).fetchall()
if rows:
(rowid, old_expire_time), = rows
if old_expire_time is None or old_expire_time > now:
sql('UPDATE Cache SET expire_time = ? WHERE rowid = ?',
(expire_time, rowid),
)
return True
return False
def add(self, key, value, expire=None, read=False, tag=None, retry=False):
"""Add `key` and `value` item to cache.
Similar to `set`, but only add to cache if key not present.
Operation is atomic. Only one concurrent add operation for a given key
will succeed.
When `read` is `True`, `value` should be a file-like object opened
for reading in binary mode.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key for item
:param value: value for item
:param float expire: seconds until the key expires
(default None, no expiry)
:param bool read: read value as bytes from file (default False)
:param str tag: text to associate with key (default None)
:param bool retry: retry if database timeout occurs (default False)
:return: True if item was added
:raises Timeout: if database timeout occurs
"""
now = time.time()
db_key, raw = self._disk.put(key)
expire_time = None if expire is None else now + expire
size, mode, filename, db_value = self._disk.store(value, read, key=key)
columns = (expire_time, tag, size, mode, filename, db_value)
with self._transact(retry, filename) as (sql, cleanup):
rows = sql(
'SELECT rowid, filename, expire_time FROM Cache'
' WHERE key = ? AND raw = ?',
(db_key, raw),
).fetchall()
if rows:
(rowid, old_filename, old_expire_time), = rows
if old_expire_time is None or old_expire_time > now:
cleanup(filename)
return False
cleanup(old_filename)
self._row_update(rowid, now, columns)
else:
self._row_insert(db_key, raw, now, columns)
self._cull(now, sql, cleanup)
return True
def incr(self, key, delta=1, default=0, retry=False):
"""Increment value by delta for item with key.
If key is missing and default is None then raise KeyError. Else if key
is missing and default is not None then use default for value.
Operation is atomic. All concurrent increment operations will be
counted individually.
Assumes value may be stored in a SQLite column. Most builds that target
machines with 64-bit pointer widths will support 64-bit signed
integers.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key for item
:param int delta: amount to increment (default 1)
:param int default: value if key is missing (default 0)
:param bool retry: retry if database timeout occurs (default False)
:return: new value for item
:raises KeyError: if key is not found and default is None
:raises Timeout: if database timeout occurs
"""
now = time.time()
db_key, raw = self._disk.put(key)
select = (
'SELECT rowid, expire_time, filename, value FROM Cache'
' WHERE key = ? AND raw = ?'
)
with self._transact(retry) as (sql, cleanup):
rows = sql(select, (db_key, raw)).fetchall()
if not rows:
if default is None:
raise KeyError(key)
value = default + delta
columns = (None, None) + self._disk.store(value, False, key=key)
self._row_insert(db_key, raw, now, columns)
self._cull(now, sql, cleanup)
return value
(rowid, expire_time, filename, value), = rows
if expire_time is not None and expire_time < now:
if default is None:
raise KeyError(key)
value = default + delta
columns = (None, None) + self._disk.store(value, False, key=key)
self._row_update(rowid, now, columns)
self._cull(now, sql, cleanup)
cleanup(filename)
return value
value += delta
columns = 'store_time = ?, value = ?'
update_column = EVICTION_POLICY[self.eviction_policy]['get']
if update_column is not None:
columns += ', ' + update_column.format(now=now)
update = 'UPDATE Cache SET %s WHERE rowid = ?' % columns
sql(update, (now, value, rowid))
return value
def decr(self, key, delta=1, default=0, retry=False):
"""Decrement value by delta for item with key.
If key is missing and default is None then raise KeyError. Else if key
is missing and default is not None then use default for value.
Operation is atomic. All concurrent decrement operations will be
counted individually.
Unlike Memcached, negative values are supported. Value may be
decremented below zero.
Assumes value may be stored in a SQLite column. Most builds that target
machines with 64-bit pointer widths will support 64-bit signed
integers.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key for item
:param int delta: amount to decrement (default 1)
:param int default: value if key is missing (default 0)
:param bool retry: retry if database timeout occurs (default False)
:return: new value for item
:raises KeyError: if key is not found and default is None
:raises Timeout: if database timeout occurs
"""
return self.incr(key, -delta, default, retry)
def get(self, key, default=None, read=False, expire_time=False, tag=False,
retry=False):
"""Retrieve value from cache. If `key` is missing, return `default`.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key for item
:param default: value to return if key is missing (default None)
:param bool read: if True, return file handle to value
(default False)
:param bool expire_time: if True, return expire_time in tuple
(default False)
:param bool tag: if True, return tag in tuple (default False)
:param bool retry: retry if database timeout occurs (default False)
:return: value for item or default if key not found
:raises Timeout: if database timeout occurs
"""
db_key, raw = self._disk.put(key)
update_column = EVICTION_POLICY[self.eviction_policy]['get']
select = (
'SELECT rowid, expire_time, tag, mode, filename, value'
' FROM Cache WHERE key = ? AND raw = ?'
' AND (expire_time IS NULL OR expire_time > ?)'
)
if expire_time and tag:
default = (default, None, None)
elif expire_time or tag:
default = (default, None)
if not self.statistics and update_column is None:
# Fast path, no transaction necessary.
rows = self._sql(select, (db_key, raw, time.time())).fetchall()
if not rows:
return default
(rowid, db_expire_time, db_tag, mode, filename, db_value), = rows
try:
value = self._disk.fetch(mode, filename, db_value, read)
except IOError:
# Key was deleted before we could retrieve result.
return default
else: # Slow path, transaction required.
cache_hit = (
'UPDATE Settings SET value = value + 1 WHERE key = "hits"'
)
cache_miss = (
'UPDATE Settings SET value = value + 1 WHERE key = "misses"'
)
with self._transact(retry) as (sql, _):
rows = sql(select, (db_key, raw, time.time())).fetchall()
if not rows:
if self.statistics:
sql(cache_miss)
return default
(rowid, db_expire_time, db_tag,
mode, filename, db_value), = rows
try:
value = self._disk.fetch(mode, filename, db_value, read)
except IOError as error:
if error.errno == errno.ENOENT:
# Key was deleted before we could retrieve result.
if self.statistics:
sql(cache_miss)
return default
else:
raise
if self.statistics:
sql(cache_hit)
now = time.time()
update = 'UPDATE Cache SET %s WHERE rowid = ?'
if update_column is not None:
sql(update % update_column.format(now=now), (rowid,))
if expire_time and tag:
return (value, db_expire_time, db_tag)
elif expire_time:
return (value, db_expire_time)
elif tag:
return (value, db_tag)
else:
return value
def __getitem__(self, key):
"""Return corresponding value for `key` from cache.
:param key: key matching item
:return: corresponding value
:raises KeyError: if key is not found
"""
value = self.get(key, default=ENOVAL, retry=True)
if value is ENOVAL:
raise KeyError(key)
return value
def read(self, key, retry=False):
"""Return file handle value corresponding to `key` from cache.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key matching item
:param bool retry: retry if database timeout occurs (default False)
:return: file open for reading in binary mode
:raises KeyError: if key is not found
:raises Timeout: if database timeout occurs
"""
handle = self.get(key, default=ENOVAL, read=True, retry=retry)
if handle is ENOVAL:
raise KeyError(key)
return handle
def __contains__(self, key):
"""Return `True` if `key` matching item is found in cache.
:param key: key matching item
:return: True if key matching item
"""
sql = self._sql
db_key, raw = self._disk.put(key)
select = (
'SELECT rowid FROM Cache'
' WHERE key = ? AND raw = ?'
' AND (expire_time IS NULL OR expire_time > ?)'
)
rows = sql(select, (db_key, raw, time.time())).fetchall()
return bool(rows)
def pop(self, key, default=None, expire_time=False, tag=False, retry=False):
"""Remove corresponding item for `key` from cache and return value.
If `key` is missing, return `default`.
Operation is atomic. Concurrent operations will be serialized.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key for item
:param default: value to return if key is missing (default None)
:param bool expire_time: if True, return expire_time in tuple
(default False)
:param bool tag: if True, return tag in tuple (default False)
:param bool retry: retry if database timeout occurs (default False)
:return: value for item or default if key not found
:raises Timeout: if database timeout occurs
"""
db_key, raw = self._disk.put(key)
select = (
'SELECT rowid, expire_time, tag, mode, filename, value'
' FROM Cache WHERE key = ? AND raw = ?'
' AND (expire_time IS NULL OR expire_time > ?)'
)
if expire_time and tag:
default = default, None, None
elif expire_time or tag:
default = default, None
with self._transact(retry) as (sql, _):
rows = sql(select, (db_key, raw, time.time())).fetchall()
if not rows:
return default
(rowid, db_expire_time, db_tag, mode, filename, db_value), = rows
sql('DELETE FROM Cache WHERE rowid = ?', (rowid,))
try:
value = self._disk.fetch(mode, filename, db_value, False)
except IOError as error:
if error.errno == errno.ENOENT:
# Key was deleted before we could retrieve result.
return default
else:
raise
finally:
if filename is not None:
self._disk.remove(filename)
if expire_time and tag:
return value, db_expire_time, db_tag
elif expire_time:
return value, db_expire_time
elif tag:
return value, db_tag
else:
return value
def __delitem__(self, key, retry=True):
"""Delete corresponding item for `key` from cache.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default `True`).
:param key: key matching item
:param bool retry: retry if database timeout occurs (default True)
:raises KeyError: if key is not found
:raises Timeout: if database timeout occurs
"""
db_key, raw = self._disk.put(key)
with self._transact(retry) as (sql, cleanup):
rows = sql(
'SELECT rowid, filename FROM Cache'
' WHERE key = ? AND raw = ?'
' AND (expire_time IS NULL OR expire_time > ?)',
(db_key, raw, time.time()),
).fetchall()
if not rows:
raise KeyError(key)
(rowid, filename), = rows
sql('DELETE FROM Cache WHERE rowid = ?', (rowid,))
cleanup(filename)
return True
def delete(self, key, retry=False):
"""Delete corresponding item for `key` from cache.
Missing keys are ignored.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param key: key matching item
:param bool retry: retry if database timeout occurs (default False)
:return: True if item was deleted
:raises Timeout: if database timeout occurs
"""
try:
return self.__delitem__(key, retry=retry)
except KeyError:
return False
def push(self, value, prefix=None, side='back', expire=None, read=False,
tag=None, retry=False):
"""Push `value` onto `side` of queue identified by `prefix` in cache.
When prefix is None, integer keys are used. Otherwise, string keys are
used in the format "prefix-integer". Integer starts at 500 trillion.
Defaults to pushing value on back of queue. Set side to 'front' to push
value on front of queue. Side must be one of 'back' or 'front'.
Operation is atomic. Concurrent operations will be serialized.
When `read` is `True`, `value` should be a file-like object opened
for reading in binary mode.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
See also `Cache.pull`.
>>> cache = Cache()
>>> print(cache.push('first value'))
500000000000000
>>> cache.get(500000000000000)
'first value'
>>> print(cache.push('second value'))
500000000000001
>>> print(cache.push('third value', side='front'))
499999999999999
>>> cache.push(1234, prefix='userids')
'userids-500000000000000'
:param value: value for item
:param str prefix: key prefix (default None, key is integer)
:param str side: either 'back' or 'front' (default 'back')
:param float expire: seconds until the key expires
(default None, no expiry)
:param bool read: read value as bytes from file (default False)
:param str tag: text to associate with key (default None)
:param bool retry: retry if database timeout occurs (default False)
:return: key for item in cache
:raises Timeout: if database timeout occurs
"""
if prefix is None:
min_key = 0
max_key = 999999999999999
else:
min_key = prefix + '-000000000000000'
max_key = prefix + '-999999999999999'
now = time.time()
raw = True
expire_time = None if expire is None else now + expire
size, mode, filename, db_value = self._disk.store(value, read)
columns = (expire_time, tag, size, mode, filename, db_value)
order = {'back': 'DESC', 'front': 'ASC'}
select = (
'SELECT key FROM Cache'
' WHERE ? < key AND key < ? AND raw = ?'
' ORDER BY key %s LIMIT 1'
) % order[side]
with self._transact(retry, filename) as (sql, cleanup):
rows = sql(select, (min_key, max_key, raw)).fetchall()
if rows:
(key,), = rows
if prefix is not None:
num = int(key[(key.rfind('-') + 1):])
else:
num = key
if side == 'back':
num += 1
else:
assert side == 'front'
num -= 1
else:
num = 500000000000000
if prefix is not None:
db_key = '{0}-{1:015d}'.format(prefix, num)
else:
db_key = num
self._row_insert(db_key, raw, now, columns)
self._cull(now, sql, cleanup)
return db_key
def pull(self, prefix=None, default=(None, None), side='front',
expire_time=False, tag=False, retry=False):
"""Pull key and value item pair from `side` of queue in cache.
When prefix is None, integer keys are used. Otherwise, string keys are
used in the format "prefix-integer". Integer starts at 500 trillion.
If queue is empty, return default.
Defaults to pulling key and value item pairs from front of queue. Set
side to 'back' to pull from back of queue. Side must be one of 'front'
or 'back'.
Operation is atomic. Concurrent operations will be serialized.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
See also `Cache.push` and `Cache.get`.
>>> cache = Cache()
>>> cache.pull()
(None, None)
>>> for letter in 'abc':
... print(cache.push(letter))
500000000000000
500000000000001
500000000000002
>>> key, value = cache.pull()
>>> print(key)
500000000000000
>>> value
'a'
>>> _, value = cache.pull(side='back')
>>> value
'c'
>>> cache.push(1234, 'userids')
'userids-500000000000000'
>>> _, value = cache.pull('userids')
>>> value
1234
:param str prefix: key prefix (default None, key is integer)
:param default: value to return if key is missing
(default (None, None))
:param str side: either 'front' or 'back' (default 'front')
:param bool expire_time: if True, return expire_time in tuple
(default False)
:param bool tag: if True, return tag in tuple (default False)
:param bool retry: retry if database timeout occurs (default False)
:return: key and value item pair or default if queue is empty
:raises Timeout: if database timeout occurs
"""
# Caution: Nearly identical code exists in Cache.peek
if prefix is None:
min_key = 0
max_key = 999999999999999
else:
min_key = prefix + '-000000000000000'
max_key = prefix + '-999999999999999'
order = {'front': 'ASC', 'back': 'DESC'}
select = (
'SELECT rowid, key, expire_time, tag, mode, filename, value'
' FROM Cache WHERE ? < key AND key < ? AND raw = 1'
' ORDER BY key %s LIMIT 1'
) % order[side]
if expire_time and tag:
default = default, None, None
elif expire_time or tag:
default = default, None
while True:
while True:
with self._transact(retry) as (sql, cleanup):
rows = sql(select, (min_key, max_key)).fetchall()
if not rows:
return default
(rowid, key, db_expire, db_tag, mode, name,
db_value), = rows
sql('DELETE FROM Cache WHERE rowid = ?', (rowid,))
if db_expire is not None and db_expire < time.time():
cleanup(name)
else:
break
try:
value = self._disk.fetch(mode, name, db_value, False)
except IOError as error:
if error.errno == errno.ENOENT:
# Key was deleted before we could retrieve result.
continue
else:
raise
finally:
if name is not None:
self._disk.remove(name)
break
if expire_time and tag:
return (key, value), db_expire, db_tag
elif expire_time:
return (key, value), db_expire
elif tag:
return (key, value), db_tag
else:
return key, value
def peek(self, prefix=None, default=(None, None), side='front',
expire_time=False, tag=False, retry=False):
"""Peek at key and value item pair from `side` of queue in cache.
When prefix is None, integer keys are used. Otherwise, string keys are
used in the format "prefix-integer". Integer starts at 500 trillion.
If queue is empty, return default.
Defaults to peeking at key and value item pairs from front of queue.
Set side to 'back' to pull from back of queue. Side must be one of
'front' or 'back'.
Expired items are deleted from cache. Operation is atomic. Concurrent
operations will be serialized.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
See also `Cache.pull` and `Cache.push`.
>>> cache = Cache()
>>> for letter in 'abc':
... print(cache.push(letter))
500000000000000
500000000000001
500000000000002
>>> key, value = cache.peek()
>>> print(key)
500000000000000
>>> value
'a'
>>> key, value = cache.peek(side='back')
>>> print(key)
500000000000002
>>> value
'c'
:param str prefix: key prefix (default None, key is integer)
:param default: value to return if key is missing
(default (None, None))
:param str side: either 'front' or 'back' (default 'front')
:param bool expire_time: if True, return expire_time in tuple
(default False)
:param bool tag: if True, return tag in tuple (default False)
:param bool retry: retry if database timeout occurs (default False)
:return: key and value item pair or default if queue is empty
:raises Timeout: if database timeout occurs
"""
# Caution: Nearly identical code exists in Cache.pull
if prefix is None:
min_key = 0
max_key = 999999999999999
else:
min_key = prefix + '-000000000000000'
max_key = prefix + '-999999999999999'
order = {'front': 'ASC', 'back': 'DESC'}
select = (
'SELECT rowid, key, expire_time, tag, mode, filename, value'
' FROM Cache WHERE ? < key AND key < ? AND raw = 1'
' ORDER BY key %s LIMIT 1'
) % order[side]
if expire_time and tag:
default = default, None, None
elif expire_time or tag:
default = default, None
while True:
while True:
with self._transact(retry) as (sql, cleanup):
rows = sql(select, (min_key, max_key)).fetchall()
if not rows:
return default
(rowid, key, db_expire, db_tag, mode, name,
db_value), = rows
if db_expire is not None and db_expire < time.time():
sql('DELETE FROM Cache WHERE rowid = ?', (rowid,))
cleanup(name)
else:
break
try:
value = self._disk.fetch(mode, name, db_value, False)
except IOError as error:
if error.errno == errno.ENOENT:
# Key was deleted before we could retrieve result.
continue
else:
raise
finally:
if name is not None:
self._disk.remove(name)
break
if expire_time and tag:
return (key, value), db_expire, db_tag
elif expire_time:
return (key, value), db_expire
elif tag:
return (key, value), db_tag
else:
return key, value
def peekitem(self, last=True, expire_time=False, tag=False, retry=False):
"""Peek at key and value item pair in cache based on iteration order.
Expired items are deleted from cache. Operation is atomic. Concurrent
operations will be serialized.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
>>> cache = Cache()
>>> for num, letter in enumerate('abc'):
... cache[letter] = num
>>> cache.peekitem()
('c', 2)
>>> cache.peekitem(last=False)
('a', 0)
:param bool last: last item in iteration order (default True)
:param bool expire_time: if True, return expire_time in tuple
(default False)
:param bool tag: if True, return tag in tuple (default False)
:param bool retry: retry if database timeout occurs (default False)
:return: key and value item pair
:raises KeyError: if cache is empty
:raises Timeout: if database timeout occurs
"""
order = ('ASC', 'DESC')
select = (
'SELECT rowid, key, raw, expire_time, tag, mode, filename, value'
' FROM Cache ORDER BY rowid %s LIMIT 1'
) % order[last]
while True:
while True:
with self._transact(retry) as (sql, cleanup):
rows = sql(select).fetchall()
if not rows:
raise KeyError('dictionary is empty')
(rowid, db_key, raw, db_expire, db_tag, mode, name,
db_value), = rows
if db_expire is not None and db_expire < time.time():
sql('DELETE FROM Cache WHERE rowid = ?', (rowid,))
cleanup(name)
else:
break
key = self._disk.get(db_key, raw)
try:
value = self._disk.fetch(mode, name, db_value, False)
except IOError as error:
if error.errno == errno.ENOENT:
# Key was deleted before we could retrieve result.
continue
else:
raise
break
if expire_time and tag:
return (key, value), db_expire, db_tag
elif expire_time:
return (key, value), db_expire
elif tag:
return (key, value), db_tag
else:
return key, value
def memoize(self, name=None, typed=False, expire=None, tag=None):
"""Memoizing cache decorator.
Decorator to wrap callable with memoizing function using cache.
Repeated calls with the same arguments will lookup result in cache and
avoid function evaluation.
If name is set to None (default), the callable name will be determined
automatically.
When expire is set to zero, function results will not be set in the
cache. Cache lookups still occur, however. Read
:doc:`case-study-landing-page-caching` for example usage.
If typed is set to True, function arguments of different types will be
cached separately. For example, f(3) and f(3.0) will be treated as
distinct calls with distinct results.
The original underlying function is accessible through the __wrapped__
attribute. This is useful for introspection, for bypassing the cache,
or for rewrapping the function with a different cache.
>>> from diskcache import Cache
>>> cache = Cache()
>>> @cache.memoize(expire=1, tag='fib')
... def fibonacci(number):
... if number == 0:
... return 0
... elif number == 1:
... return 1
... else:
... return fibonacci(number - 1) + fibonacci(number - 2)
>>> print(fibonacci(100))
354224848179261915075
An additional `__cache_key__` attribute can be used to generate the
cache key used for the given arguments.
>>> key = fibonacci.__cache_key__(100)
>>> print(cache[key])
354224848179261915075
Remember to call memoize when decorating a callable. If you forget,
then a TypeError will occur. Note the lack of parenthenses after
memoize below:
>>> @cache.memoize
... def test():
... pass
Traceback (most recent call last):
...
TypeError: name cannot be callable
:param cache: cache to store callable arguments and return values
:param str name: name given for callable (default None, automatic)
:param bool typed: cache different types separately (default False)
:param float expire: seconds until arguments expire
(default None, no expiry)
:param str tag: text to associate with arguments (default None)
:return: callable decorator
"""
# Caution: Nearly identical code exists in DjangoCache.memoize
if callable(name):
raise TypeError('name cannot be callable')
def decorator(func):
"Decorator created by memoize() for callable `func`."
base = (full_name(func),) if name is None else (name,)
@ft.wraps(func)
def wrapper(*args, **kwargs):
"Wrapper for callable to cache arguments and return values."
key = wrapper.__cache_key__(*args, **kwargs)
result = self.get(key, default=ENOVAL, retry=True)
if result is ENOVAL:
result = func(*args, **kwargs)
if expire is None or expire > 0:
self.set(key, result, expire, tag=tag, retry=True)
return result
def __cache_key__(*args, **kwargs):
"Make key for cache given function arguments."
return args_to_key(base, args, kwargs, typed)
wrapper.__cache_key__ = __cache_key__
return wrapper
return decorator
def check(self, fix=False, retry=False):
"""Check database and file system consistency.
Intended for use in testing and post-mortem error analysis.
While checking the Cache table for consistency, a writer lock is held
on the database. The lock blocks other cache clients from writing to
the database. For caches with many file references, the lock may be
held for a long time. For example, local benchmarking shows that a
cache with 1,000 file references takes ~60ms to check.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param bool fix: correct inconsistencies
:param bool retry: retry if database timeout occurs (default False)
:return: list of warnings
:raises Timeout: if database timeout occurs
"""
# pylint: disable=access-member-before-definition,W0201
with warnings.catch_warnings(record=True) as warns:
sql = self._sql
# Check integrity of database.
rows = sql('PRAGMA integrity_check').fetchall()
if len(rows) != 1 or rows[0][0] != u'ok':
for message, in rows:
warnings.warn(message)
if fix:
sql('VACUUM')
with self._transact(retry) as (sql, _):
# Check Cache.filename against file system.
filenames = set()
select = (
'SELECT rowid, size, filename FROM Cache'
' WHERE filename IS NOT NULL'
)
rows = sql(select).fetchall()
for rowid, size, filename in rows:
full_path = op.join(self._directory, filename)
filenames.add(full_path)
if op.exists(full_path):
real_size = op.getsize(full_path)
if size != real_size:
message = 'wrong file size: %s, %d != %d'
args = full_path, real_size, size
warnings.warn(message % args)
if fix:
sql('UPDATE Cache SET size = ?'
' WHERE rowid = ?',
(real_size, rowid),
)
continue
warnings.warn('file not found: %s' % full_path)
if fix:
sql('DELETE FROM Cache WHERE rowid = ?', (rowid,))
# Check file system against Cache.filename.
for dirpath, _, files in os.walk(self._directory):
paths = [op.join(dirpath, filename) for filename in files]
error = set(paths) - filenames
for full_path in error:
if DBNAME in full_path:
continue
message = 'unknown file: %s' % full_path
warnings.warn(message, UnknownFileWarning)
if fix:
os.remove(full_path)
# Check for empty directories.
for dirpath, dirs, files in os.walk(self._directory):
if not (dirs or files):
message = 'empty directory: %s' % dirpath
warnings.warn(message, EmptyDirWarning)
if fix:
os.rmdir(dirpath)
# Check Settings.count against count of Cache rows.
self.reset('count')
(count,), = sql('SELECT COUNT(key) FROM Cache').fetchall()
if self.count != count:
message = 'Settings.count != COUNT(Cache.key); %d != %d'
warnings.warn(message % (self.count, count))
if fix:
sql('UPDATE Settings SET value = ? WHERE key = ?',
(count, 'count'),
)
# Check Settings.size against sum of Cache.size column.
self.reset('size')
select_size = 'SELECT COALESCE(SUM(size), 0) FROM Cache'
(size,), = sql(select_size).fetchall()
if self.size != size:
message = 'Settings.size != SUM(Cache.size); %d != %d'
warnings.warn(message % (self.size, size))
if fix:
sql('UPDATE Settings SET value = ? WHERE key =?',
(size, 'size'),
)
return warns
def create_tag_index(self):
"""Create tag index on cache database.
It is better to initialize cache with `tag_index=True` than use this.
:raises Timeout: if database timeout occurs
"""
sql = self._sql
sql('CREATE INDEX IF NOT EXISTS Cache_tag_rowid ON Cache(tag, rowid)')
self.reset('tag_index', 1)
def drop_tag_index(self):
"""Drop tag index on cache database.
:raises Timeout: if database timeout occurs
"""
sql = self._sql
sql('DROP INDEX IF EXISTS Cache_tag_rowid')
self.reset('tag_index', 0)
def evict(self, tag, retry=False):
"""Remove items with matching `tag` from cache.
Removing items is an iterative process. In each iteration, a subset of
items is removed. Concurrent writes may occur between iterations.
If a :exc:`Timeout` occurs, the first element of the exception's
`args` attribute will be the number of items removed before the
exception occurred.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param str tag: tag identifying items
:param bool retry: retry if database timeout occurs (default False)
:return: count of rows removed
:raises Timeout: if database timeout occurs
"""
select = (
'SELECT rowid, filename FROM Cache'
' WHERE tag = ? AND rowid > ?'
' ORDER BY rowid LIMIT ?'
)
args = [tag, 0, 100]
return self._select_delete(select, args, arg_index=1, retry=retry)
def expire(self, now=None, retry=False):
"""Remove expired items from cache.
Removing items is an iterative process. In each iteration, a subset of
items is removed. Concurrent writes may occur between iterations.
If a :exc:`Timeout` occurs, the first element of the exception's
`args` attribute will be the number of items removed before the
exception occurred.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param float now: current time (default None, ``time.time()`` used)
:param bool retry: retry if database timeout occurs (default False)
:return: count of items removed
:raises Timeout: if database timeout occurs
"""
select = (
'SELECT rowid, expire_time, filename FROM Cache'
' WHERE ? < expire_time AND expire_time < ?'
' ORDER BY expire_time LIMIT ?'
)
args = [0, now or time.time(), 100]
return self._select_delete(select, args, row_index=1, retry=retry)
def cull(self, retry=False):
"""Cull items from cache until volume is less than size limit.
Removing items is an iterative process. In each iteration, a subset of
items is removed. Concurrent writes may occur between iterations.
If a :exc:`Timeout` occurs, the first element of the exception's
`args` attribute will be the number of items removed before the
exception occurred.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param bool retry: retry if database timeout occurs (default False)
:return: count of items removed
:raises Timeout: if database timeout occurs
"""
now = time.time()
# Remove expired items.
count = self.expire(now)
# Remove items by policy.
select_policy = EVICTION_POLICY[self.eviction_policy]['cull']
if select_policy is None:
return
select_filename = select_policy.format(fields='filename', now=now)
try:
while self.volume() > self.size_limit:
with self._transact(retry) as (sql, cleanup):
rows = sql(select_filename, (10,)).fetchall()
if not rows:
break
count += len(rows)
delete = (
'DELETE FROM Cache WHERE rowid IN (%s)'
% select_policy.format(fields='rowid', now=now)
)
sql(delete, (10,))
for filename, in rows:
cleanup(filename)
except Timeout:
raise Timeout(count)
return count
def clear(self, retry=False):
"""Remove all items from cache.
Removing items is an iterative process. In each iteration, a subset of
items is removed. Concurrent writes may occur between iterations.
If a :exc:`Timeout` occurs, the first element of the exception's
`args` attribute will be the number of items removed before the
exception occurred.
Raises :exc:`Timeout` error when database timeout occurs and `retry` is
`False` (default).
:param bool retry: retry if database timeout occurs (default False)
:return: count of rows removed
:raises Timeout: if database timeout occurs
"""
select = (
'SELECT rowid, filename FROM Cache'
' WHERE rowid > ?'
' ORDER BY rowid LIMIT ?'
)
args = [0, 100]
return self._select_delete(select, args, retry=retry)
def _select_delete(self, select, args, row_index=0, arg_index=0,
retry=False):
count = 0
delete = 'DELETE FROM Cache WHERE rowid IN (%s)'
try:
while True:
with self._transact(retry) as (sql, cleanup):
rows = sql(select, args).fetchall()
if not rows:
break
count += len(rows)
sql(delete % ','.join(str(row[0]) for row in rows))
for row in rows:
args[arg_index] = row[row_index]
cleanup(row[-1])
except Timeout:
raise Timeout(count)
return count
def iterkeys(self, reverse=False):
"""Iterate Cache keys in database sort order.
>>> cache = Cache()
>>> for key in [4, 1, 3, 0, 2]:
... cache[key] = key
>>> list(cache.iterkeys())
[0, 1, 2, 3, 4]
>>> list(cache.iterkeys(reverse=True))
[4, 3, 2, 1, 0]
:param bool reverse: reverse sort order (default False)
:return: iterator of Cache keys
"""
sql = self._sql
limit = 100
_disk_get = self._disk.get
if reverse:
select = (
'SELECT key, raw FROM Cache'
' ORDER BY key DESC, raw DESC LIMIT 1'
)
iterate = (
'SELECT key, raw FROM Cache'
' WHERE key = ? AND raw < ? OR key < ?'
' ORDER BY key DESC, raw DESC LIMIT ?'
)
else:
select = (
'SELECT key, raw FROM Cache'
' ORDER BY key ASC, raw ASC LIMIT 1'
)
iterate = (
'SELECT key, raw FROM Cache'
' WHERE key = ? AND raw > ? OR key > ?'
' ORDER BY key ASC, raw ASC LIMIT ?'
)
row = sql(select).fetchall()
if row:
(key, raw), = row
else:
return
yield _disk_get(key, raw)
while True:
rows = sql(iterate, (key, raw, key, limit)).fetchall()
if not rows:
break
for key, raw in rows:
yield _disk_get(key, raw)
def _iter(self, ascending=True):
sql = self._sql
rows = sql('SELECT MAX(rowid) FROM Cache').fetchall()
(max_rowid,), = rows
yield # Signal ready.
if max_rowid is None:
return
bound = max_rowid + 1
limit = 100
_disk_get = self._disk.get
rowid = 0 if ascending else bound
select = (
'SELECT rowid, key, raw FROM Cache'
' WHERE ? < rowid AND rowid < ?'
' ORDER BY rowid %s LIMIT ?'
) % ('ASC' if ascending else 'DESC')
while True:
if ascending:
args = (rowid, bound, limit)
else:
args = (0, rowid, limit)
rows = sql(select, args).fetchall()
if not rows:
break
for rowid, key, raw in rows:
yield _disk_get(key, raw)
def __iter__(self):
"Iterate keys in cache including expired items."
iterator = self._iter()
next(iterator)
return iterator
def __reversed__(self):
"Reverse iterate keys in cache including expired items."
iterator = self._iter(ascending=False)
next(iterator)
return iterator
def stats(self, enable=True, reset=False):
"""Return cache statistics hits and misses.
:param bool enable: enable collecting statistics (default True)
:param bool reset: reset hits and misses to 0 (default False)
:return: (hits, misses)
"""
# pylint: disable=E0203,W0201
result = (self.reset('hits'), self.reset('misses'))
if reset:
self.reset('hits', 0)
self.reset('misses', 0)
self.reset('statistics', enable)
return result
def volume(self):
"""Return estimated total size of cache on disk.
:return: size in bytes
"""
(page_count,), = self._sql('PRAGMA page_count').fetchall()
total_size = self._page_size * page_count + self.reset('size')
return total_size
def close(self):
"""Close database connection.
"""
con = getattr(self._local, 'con', None)
if con is None:
return
con.close()
try:
delattr(self._local, 'con')
except AttributeError:
pass
def __enter__(self):
# Create connection in thread.
connection = self._con # pylint: disable=unused-variable
return self
def __exit__(self, *exception):
self.close()
def __len__(self):
"Count of items in cache including expired items."
return self.reset('count')
def __getstate__(self):
return (self.directory, self.timeout, type(self.disk))
def __setstate__(self, state):
self.__init__(*state)
def reset(self, key, value=ENOVAL, update=True):
"""Reset `key` and `value` item from Settings table.
Use `reset` to update the value of Cache settings correctly. Cache
settings are stored in the Settings table of the SQLite database. If
`update` is ``False`` then no attempt is made to update the database.
If `value` is not given, it is reloaded from the Settings
table. Otherwise, the Settings table is updated.
Settings with the ``disk_`` prefix correspond to Disk
attributes. Updating the value will change the unprefixed attribute on
the associated Disk instance.
Settings with the ``sqlite_`` prefix correspond to SQLite
pragmas. Updating the value will execute the corresponding PRAGMA
statement.
SQLite PRAGMA statements may be executed before the Settings table
exists in the database by setting `update` to ``False``.
:param str key: Settings key for item
:param value: value for item (optional)
:param bool update: update database Settings table (default True)
:return: updated value for item
:raises Timeout: if database timeout occurs
"""
sql = self._sql
sql_retry = self._sql_retry
if value is ENOVAL:
select = 'SELECT value FROM Settings WHERE key = ?'
(value,), = sql_retry(select, (key,)).fetchall()
setattr(self, key, value)
return value
if update:
statement = 'UPDATE Settings SET value = ? WHERE key = ?'
sql_retry(statement, (value, key))
if key.startswith('sqlite_'):
pragma = key[7:]
# 2016-02-17 GrantJ - PRAGMA and isolation_level=None
# don't always play nicely together. Retry setting the
# PRAGMA. I think some PRAGMA statements expect to
# immediately take an EXCLUSIVE lock on the database. I
# can't find any documentation for this but without the
# retry, stress will intermittently fail with multiple
# processes.
# 2018-11-05 GrantJ - Avoid setting pragma values that
# are already set. Pragma settings like auto_vacuum and
# journal_mode can take a long time or may not work after
# tables have been created.
start = time.time()
while True:
try:
try:
(old_value,), = sql('PRAGMA %s' % (pragma)).fetchall()
update = old_value != value
except ValueError:
update = True
if update:
sql('PRAGMA %s = %s' % (pragma, value)).fetchall()
break
except sqlite3.OperationalError as exc:
if str(exc) != 'database is locked':
raise
diff = time.time() - start
if diff > 60:
raise
time.sleep(0.001)
elif key.startswith('disk_'):
attr = key[5:]
setattr(self._disk, attr, value)
setattr(self, key, value)
return value