Lock.release() - Code Metrics - ionelmc/python-redis-lock - Measure and Improve Code Quality continuously with Scrutinizer

Lock.release() A
last analyzed 2016-10-29 17:21 UTC

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Complexity

Conditions

Size

Total Lines

Duplication

Lines	0
Ratio	0 %

Importance

Changes	5
Bugs	0	Features	0

Metric	Value
cc	4
c	5
b	0
f	0
dl	0
loc	20
rs	9.2

import threading
from logging import getLogger
from os import urandom
from hashlib import sha1
import weakref

from redis import StrictRedis
from redis.exceptions import NoScriptError

__version__ = "3.2.0"

logger = getLogger(__name__)

# Check if the id match. If not, return an error code.
UNLOCK_SCRIPT = b"""
    if redis.call("get", KEYS[1]) ~= ARGV[1] then
        return 1
    else
        redis.call("del", KEYS[2])
        redis.call("lpush", KEYS[2], 1)
        redis.call("del", KEYS[1])
        return 0
    end
"""
UNLOCK_SCRIPT_HASH = sha1(UNLOCK_SCRIPT).hexdigest()

# Covers both cases when key doesn't exist and doesn't equal to lock's id
EXTEND_SCRIPT = b"""
    if redis.call("get", KEYS[1]) ~= ARGV[2] then
        return 1
    elseif redis.call("ttl", KEYS[1]) < 0 then
        return 2
    else
        redis.call("expire", KEYS[1], ARGV[1])
        return 0
    end
"""
EXTEND_SCRIPT_HASH = sha1(EXTEND_SCRIPT).hexdigest()

RESET_SCRIPT = b"""
    redis.call('del', KEYS[2])
    redis.call('lpush', KEYS[2], 1)
    return redis.call('del', KEYS[1])
"""

RESET_SCRIPT_HASH = sha1(RESET_SCRIPT).hexdigest()

RESET_ALL_SCRIPT = b"""
    local locks = redis.call('keys', 'lock:*')
    local signal
    for _, lock in pairs(locks) do
        signal = 'lock-signal:' .. string.sub(lock, 6)
        redis.call('del', signal)
        redis.call('lpush', signal, 1)
        redis.call('del', lock)
    end
    return #locks
"""

RESET_ALL_SCRIPT_HASH = sha1(RESET_ALL_SCRIPT).hexdigest()

DELETE_ALL_SIGNAL_KEYS_SCRIPT = b"""
    local signals = redis.call('keys', 'lock-signal:*')
    for _, signal in pairs(signals) do
        redis.call('del', signal)
    end
    return #signals
"""

DELETE_ALL_SIGNAL_KEYS_SCRIPT_HASH = (sha1(DELETE_ALL_SIGNAL_KEYS_SCRIPT)
                                      .hexdigest())


class AlreadyAcquired(RuntimeError):
    pass


class NotAcquired(RuntimeError):
    pass


class AlreadyStarted(RuntimeError):
    pass


class TimeoutNotUsable(RuntimeError):
    pass


class InvalidTimeout(RuntimeError):
    pass


class TimeoutTooLarge(RuntimeError):
    pass


class NotExpirable(RuntimeError):
    pass


((UNLOCK, _, _,   # noqa
  EXTEND, _, _,
  RESET, _, _,
  RESET_ALL, _, _,
  DELETE_ALL_SIGNAL_KEYS, _, _),
 SCRIPTS) = zip(*enumerate([
    UNLOCK_SCRIPT_HASH, UNLOCK_SCRIPT, 'UNLOCK_SCRIPT',
    EXTEND_SCRIPT_HASH, EXTEND_SCRIPT, 'EXTEND_SCRIPT',
    RESET_SCRIPT_HASH, RESET_SCRIPT, 'RESET_SCRIPT',
    RESET_ALL_SCRIPT_HASH, RESET_ALL_SCRIPT, 'RESET_ALL_SCRIPT',
    DELETE_ALL_SIGNAL_KEYS_SCRIPT_HASH, DELETE_ALL_SIGNAL_KEYS_SCRIPT,
    'DELETE_ALL_SIGNAL_KEYS_SCRIPT'
]))


def _eval_script(redis, script_id, *keys, **kwargs):
    """Tries to call ``EVALSHA`` with the `hash` and then, if it fails, calls
    regular ``EVAL`` with the `script`.
    """
    args = kwargs.pop('args', ())
    if kwargs:
        raise TypeError("Unexpected keyword arguments %s" % kwargs.keys())
    try:
        return redis.evalsha(SCRIPTS[script_id], len(keys), *keys + args)
    except NoScriptError:
        logger.warn("%s not cached.", SCRIPTS[script_id + 2])
        return redis.eval(SCRIPTS[script_id + 1], len(keys), *keys + args)


class Lock(object):
    """
    A Lock context manager implemented via redis SETNX/BLPOP.
    """

    def __init__(self, redis_client, name, expire=None, id=None, auto_renewal=False, strict=True):
        """
        :param redis_client:
            An instance of :class:`~StrictRedis`.
        :param name:
            The name (redis key) the lock should have.
        :param expire:
            The lock expiry time in seconds. If left at the default (None)
            the lock will not expire.
        :param id:
            The ID (redis value) the lock should have. A random value is
            generated when left at the default.

            Note that if you specify this then the lock is marked as "held". Acquires
            won't be possible.
        :param auto_renewal:
            If set to ``True``, Lock will automatically renew the lock so that it
            doesn't expire for as long as the lock is held (acquire() called
            or running in a context manager).

            Implementation note: Renewal will happen using a daemon thread with
            an interval of ``expire*2/3``. If wishing to use a different renewal
            time, subclass Lock, call ``super().__init__()`` then set
            ``self._lock_renewal_interval`` to your desired interval.
        :param strict:
            If set ``True`` then the ``redis_client`` needs to be an instance of ``redis.StrictRedis``.
        """
        if strict and not isinstance(redis_client, StrictRedis):
            raise ValueError("redis_client must be instance of StrictRedis. "
                             "Use strict=False if you know what you're doing.")
        if auto_renewal and expire is None:
            raise ValueError("Expire may not be None when auto_renewal is set")

        self._client = redis_client
        self._expire = expire if expire is None else int(expire)
        if id is None:
            self._id = urandom(16)
        elif isinstance(id, bytes):
            self._id = id
        else:
            raise TypeError("Incorrect type for `id`. Must be bytes not %s." % type(id))
        self._name = 'lock:'+name
        self._signal = 'lock-signal:'+name
        self._lock_renewal_interval = (float(expire)*2/3
                                       if auto_renewal
                                       else None)
        self._lock_renewal_thread = None

    @property
    def _held(self):
        return self.id == self.get_owner_id()

    def reset(self):
        """
        Forcibly deletes the lock. Use this with care.
        """
        _eval_script(self._client, RESET, self._name, self._signal)
        self._delete_signal()

    @property
    def id(self):
        return self._id

    def get_owner_id(self):
        return self._client.get(self._name)

    def acquire(self, blocking=True, timeout=None):
        """
        :param blocking:
            Boolean value specifying whether lock should be blocking or not.
        :param timeout:
            An integer value specifying the maximum number of seconds to block.
        """
        logger.debug("Getting %r ...", self._name)

        if self._held:
            raise AlreadyAcquired("Already acquired from this Lock instance.")

        if not blocking and timeout is not None:
            raise TimeoutNotUsable("Timeout cannot be used if blocking=False")

        timeout = timeout if timeout is None else int(timeout)
        if timeout is not None and timeout <= 0:
            raise InvalidTimeout("Timeout (%d) cannot be less than or equal to 0" % timeout)

        if timeout and self._expire and timeout > self._expire:
            raise TimeoutTooLarge("Timeout (%d) cannot be greater than expire (%d)" % (timeout, self._expire))

        busy = True
        blpop_timeout = timeout or self._expire or 0
        timed_out = False
        while busy:
            busy = not self._client.set(self._name, self._id, nx=True, ex=self._expire)
            if busy:
                if timed_out:
                    return False
                elif blocking:
                    timed_out = not self._client.blpop(self._signal, blpop_timeout) and timeout
                else:
                    logger.debug("Failed to get %r.", self._name)
                    return False

        logger.debug("Got lock for %r.", self._name)
        if self._lock_renewal_interval is not None:
            self._start_lock_renewer()
        return True

    def extend(self, expire=None):
        """Extends expiration time of the lock.

        :param expire:
            New expiration time. If ``None`` - `expire` provided during
            lock initialization will be taken.
        """
        if expire is None:
            if self._expire is not None:
                expire = self._expire
            else:
                raise TypeError(
                    "To extend a lock 'expire' must be provided as an "
                    "argument to extend() method or at initialization time."
                )
        error = _eval_script(self._client, EXTEND, self._name, args=(expire, self._id))
        if error == 1:
            raise NotAcquired("Lock %s is not acquired or it already expired." % self._name)
        elif error == 2:
            raise NotExpirable("Lock %s has no assigned expiration time" %
                               self._name)
        elif error:
            raise RuntimeError("Unsupported error code %s from EXTEND script" % error)

    @staticmethod
    def _lock_renewer(lockref, interval, stop):
        """
        Renew the lock key in redis every `interval` seconds for as long
        as `self._lock_renewal_thread.should_exit` is False.
        """
        log = getLogger("%s.lock_refresher" % __name__)
        while not stop.wait(timeout=interval):
            log.debug("Refreshing lock")
            lock = lockref()
            if lock is None:
                log.debug("The lock no longer exists, "
                          "stopping lock refreshing")
                break
            lock.extend(expire=lock._expire)
            del lock
        log.debug("Exit requested, stopping lock refreshing")

    def _start_lock_renewer(self):
        """
        Starts the lock refresher thread.
        """
        if self._lock_renewal_thread is not None:
            raise AlreadyStarted("Lock refresh thread already started")

        logger.debug(
            "Starting thread to refresh lock every %s seconds",
            self._lock_renewal_interval
        )
        self._lock_renewal_stop = threading.Event()
        self._lock_renewal_thread = threading.Thread(
            group=None,
            target=self._lock_renewer,
            kwargs={'lockref': weakref.ref(self),
                    'interval': self._lock_renewal_interval,
                    'stop': self._lock_renewal_stop}
        )
        self._lock_renewal_thread.setDaemon(True)
        self._lock_renewal_thread.start()

    def _stop_lock_renewer(self):
        """
        Stop the lock renewer.

        This signals the renewal thread and waits for its exit.
        """
        if self._lock_renewal_thread is None or not self._lock_renewal_thread.is_alive():
            return
        logger.debug("Signalling the lock refresher to stop")
        self._lock_renewal_stop.set()
        self._lock_renewal_thread.join()
        self._lock_renewal_thread = None
        logger.debug("Lock refresher has stopped")

    def __enter__(self):
        acquired = self.acquire(blocking=True)
        assert acquired, "Lock wasn't acquired, but blocking=True"
        return self

    def __exit__(self, exc_type=None, exc_value=None, traceback=None):
        self.release()

    def release(self):
        """Releases the lock, that was acquired with the same object.

        .. note::

            If you want to release a lock that you acquired in a different place you have two choices:

            * Use ``Lock("name", id=id_from_other_place).release()``
            * Use ``Lock("name").reset()``
        """
        if self._lock_renewal_thread is not None:
            self._stop_lock_renewer()
        logger.debug("Releasing %r.", self._name)
        error = _eval_script(self._client, UNLOCK, self._name, self._signal, args=(self._id,))
        if error == 1:
            raise NotAcquired("Lock %s is not acquired or it already expired." % self._name)
        elif error:
            raise RuntimeError("Unsupported error code %s from EXTEND script." % error)
        else:
            self._delete_signal()

    def _delete_signal(self):
        self._client.delete(self._signal)


def reset_all(redis_client):
    """
    Forcibly deletes all locks if its remains (like a crash reason). Use this with care.
    """
    _eval_script(redis_client, RESET_ALL)
    _eval_script(redis_client, DELETE_ALL_SIGNAL_KEYS)


1			import threading
2			from logging import getLogger
3			from os import urandom
4			from hashlib import sha1
5			import weakref
6
7			from redis import StrictRedis
8			from redis.exceptions import NoScriptError
9
10			__version__ = "3.2.0"
11
12			logger = getLogger(__name__)
13
14			# Check if the id match. If not, return an error code.
15			UNLOCK_SCRIPT = b"""
16			if redis.call("get", KEYS[1]) ~= ARGV[1] then
17			return 1
18			else
19			redis.call("del", KEYS[2])
20			redis.call("lpush", KEYS[2], 1)
21			redis.call("del", KEYS[1])
22			return 0
23			end
24			"""
25			UNLOCK_SCRIPT_HASH = sha1(UNLOCK_SCRIPT).hexdigest()
26
27			# Covers both cases when key doesn't exist and doesn't equal to lock's id
28			EXTEND_SCRIPT = b"""
29			if redis.call("get", KEYS[1]) ~= ARGV[2] then
30			return 1
31			elseif redis.call("ttl", KEYS[1]) < 0 then
32			return 2
33			else
34			redis.call("expire", KEYS[1], ARGV[1])
35			return 0
36			end
37			"""
38			EXTEND_SCRIPT_HASH = sha1(EXTEND_SCRIPT).hexdigest()
39
40			RESET_SCRIPT = b"""
41			redis.call('del', KEYS[2])
42			redis.call('lpush', KEYS[2], 1)
43			return redis.call('del', KEYS[1])
44			"""
45
46			RESET_SCRIPT_HASH = sha1(RESET_SCRIPT).hexdigest()
47
48			RESET_ALL_SCRIPT = b"""
49			local locks = redis.call('keys', 'lock:*')
50			local signal
51			for _, lock in pairs(locks) do
52			signal = 'lock-signal:' .. string.sub(lock, 6)
53			redis.call('del', signal)
54			redis.call('lpush', signal, 1)
55			redis.call('del', lock)
56			end
57			return #locks
58			"""
59
60			RESET_ALL_SCRIPT_HASH = sha1(RESET_ALL_SCRIPT).hexdigest()
61
62			DELETE_ALL_SIGNAL_KEYS_SCRIPT = b"""
63			local signals = redis.call('keys', 'lock-signal:*')
64			for _, signal in pairs(signals) do
65			redis.call('del', signal)
66			end
67			return #signals
68			"""
69
70			DELETE_ALL_SIGNAL_KEYS_SCRIPT_HASH = (sha1(DELETE_ALL_SIGNAL_KEYS_SCRIPT)
71			.hexdigest())
72
73
74			class AlreadyAcquired(RuntimeError):
75			pass
76
77
78			class NotAcquired(RuntimeError):
79			pass
80
81
82			class AlreadyStarted(RuntimeError):
83			pass
84
85
86			class TimeoutNotUsable(RuntimeError):
87			pass
88
89
90			class InvalidTimeout(RuntimeError):
91			pass
92
93
94			class TimeoutTooLarge(RuntimeError):
95			pass
96
97
98			class NotExpirable(RuntimeError):
99			pass
100
101
102			((UNLOCK, _, _, # noqa
103			EXTEND, _, _,
104			RESET, _, _,
105			RESET_ALL, _, _,
106			DELETE_ALL_SIGNAL_KEYS, _, _),
107			SCRIPTS) = zip(*enumerate([
108			UNLOCK_SCRIPT_HASH, UNLOCK_SCRIPT, 'UNLOCK_SCRIPT',
109			EXTEND_SCRIPT_HASH, EXTEND_SCRIPT, 'EXTEND_SCRIPT',
110			RESET_SCRIPT_HASH, RESET_SCRIPT, 'RESET_SCRIPT',
111			RESET_ALL_SCRIPT_HASH, RESET_ALL_SCRIPT, 'RESET_ALL_SCRIPT',
112			DELETE_ALL_SIGNAL_KEYS_SCRIPT_HASH, DELETE_ALL_SIGNAL_KEYS_SCRIPT,
113			'DELETE_ALL_SIGNAL_KEYS_SCRIPT'
114			]))
115
116
117			def _eval_script(redis, script_id, keys, *kwargs):
118			"""Tries to call ``EVALSHA`` with the `hash` and then, if it fails, calls
119			regular ``EVAL`` with the `script`.
120			"""
121			args = kwargs.pop('args', ())
122			if kwargs:
123			raise TypeError("Unexpected keyword arguments %s" % kwargs.keys())
124			try:
125			return redis.evalsha(SCRIPTS[script_id], len(keys), *keys + args)
126			except NoScriptError:
127			logger.warn("%s not cached.", SCRIPTS[script_id + 2])
128			return redis.eval(SCRIPTS[script_id + 1], len(keys), *keys + args)
129
130
131			class Lock(object):
132			"""
133			A Lock context manager implemented via redis SETNX/BLPOP.
134			"""
135
136			def __init__(self, redis_client, name, expire=None, id=None, auto_renewal=False, strict=True):
137			"""
138			:param redis_client:
139			An instance of :class:`~StrictRedis`.
140			:param name:
141			The name (redis key) the lock should have.
142			:param expire:
143			The lock expiry time in seconds. If left at the default (None)
144			the lock will not expire.
145			:param id:
146			The ID (redis value) the lock should have. A random value is
147			generated when left at the default.
148
149			Note that if you specify this then the lock is marked as "held". Acquires
150			won't be possible.
151			:param auto_renewal:
152			If set to ``True``, Lock will automatically renew the lock so that it
153			doesn't expire for as long as the lock is held (acquire() called
154			or running in a context manager).
155
156			Implementation note: Renewal will happen using a daemon thread with
157			an interval of ``expire*2/3``. If wishing to use a different renewal
158			time, subclass Lock, call ``super().__init__()`` then set
159			``self._lock_renewal_interval`` to your desired interval.
160			:param strict:
161			If set ``True`` then the ``redis_client`` needs to be an instance of ``redis.StrictRedis``.
162			"""
163			if strict and not isinstance(redis_client, StrictRedis):
164			raise ValueError("redis_client must be instance of StrictRedis. "
165			"Use strict=False if you know what you're doing.")
166			if auto_renewal and expire is None:
167			raise ValueError("Expire may not be None when auto_renewal is set")
168
169			self._client = redis_client
170			self._expire = expire if expire is None else int(expire)
171			if id is None:
172			self._id = urandom(16)
173			elif isinstance(id, bytes):
174			self._id = id
175			else:
176			raise TypeError("Incorrect type for `id`. Must be bytes not %s." % type(id))
177			self._name = 'lock:'+name
178			self._signal = 'lock-signal:'+name
179			self._lock_renewal_interval = (float(expire)*2/3
180			if auto_renewal
181			else None)
182			self._lock_renewal_thread = None
183
184			@property
185			def _held(self):
186			return self.id == self.get_owner_id()
187
188			def reset(self):
189			"""
190			Forcibly deletes the lock. Use this with care.
191			"""
192			_eval_script(self._client, RESET, self._name, self._signal)
193			self._delete_signal()
194
195			@property
196			def id(self):
197			return self._id
198
199			def get_owner_id(self):
200			return self._client.get(self._name)
201
202			def acquire(self, blocking=True, timeout=None):
203			"""
204			:param blocking:
205			Boolean value specifying whether lock should be blocking or not.
206			:param timeout:
207			An integer value specifying the maximum number of seconds to block.
208			"""
209			logger.debug("Getting %r ...", self._name)
210
211			if self._held:
212			raise AlreadyAcquired("Already acquired from this Lock instance.")
213
214			if not blocking and timeout is not None:
215			raise TimeoutNotUsable("Timeout cannot be used if blocking=False")
216
217			timeout = timeout if timeout is None else int(timeout)
218			if timeout is not None and timeout <= 0:
219			raise InvalidTimeout("Timeout (%d) cannot be less than or equal to 0" % timeout)
220
221			if timeout and self._expire and timeout > self._expire:
222			raise TimeoutTooLarge("Timeout (%d) cannot be greater than expire (%d)" % (timeout, self._expire))
223
224			busy = True
225			blpop_timeout = timeout or self._expire or 0
226			timed_out = False
227			while busy:
228			busy = not self._client.set(self._name, self._id, nx=True, ex=self._expire)
229			if busy:
230			if timed_out:
231			return False
232			elif blocking:
233			timed_out = not self._client.blpop(self._signal, blpop_timeout) and timeout
234			else:
235			logger.debug("Failed to get %r.", self._name)
236			return False
237
238			logger.debug("Got lock for %r.", self._name)
239			if self._lock_renewal_interval is not None:
240			self._start_lock_renewer()
241			return True
242
243			def extend(self, expire=None):
244			"""Extends expiration time of the lock.
245
246			:param expire:
247			New expiration time. If ``None`` - `expire` provided during
248			lock initialization will be taken.
249			"""
250			if expire is None:
251			if self._expire is not None:
252			expire = self._expire
253			else:
254			raise TypeError(
255			"To extend a lock 'expire' must be provided as an "
256			"argument to extend() method or at initialization time."
257			)
258			error = _eval_script(self._client, EXTEND, self._name, args=(expire, self._id))
259			if error == 1:
260			raise NotAcquired("Lock %s is not acquired or it already expired." % self._name)
261			elif error == 2:
262			raise NotExpirable("Lock %s has no assigned expiration time" %
263			self._name)
264			elif error:
265			raise RuntimeError("Unsupported error code %s from EXTEND script" % error)
266
267			@staticmethod
268			def _lock_renewer(lockref, interval, stop):
269			"""
270			Renew the lock key in redis every `interval` seconds for as long
271			as `self._lock_renewal_thread.should_exit` is False.
272			"""
273			log = getLogger("%s.lock_refresher" % __name__)
274			while not stop.wait(timeout=interval):
275			log.debug("Refreshing lock")
276			lock = lockref()
277			if lock is None:
278			log.debug("The lock no longer exists, "
279			"stopping lock refreshing")
280			break
281			lock.extend(expire=lock._expire)
282			del lock
283			log.debug("Exit requested, stopping lock refreshing")
284
285			def _start_lock_renewer(self):
286			"""
287			Starts the lock refresher thread.
288			"""
289			if self._lock_renewal_thread is not None:
290			raise AlreadyStarted("Lock refresh thread already started")
291
292			logger.debug(
293			"Starting thread to refresh lock every %s seconds",
294			self._lock_renewal_interval
295			)
296			self._lock_renewal_stop = threading.Event()
297			self._lock_renewal_thread = threading.Thread(
298			group=None,
299			target=self._lock_renewer,
300			kwargs={'lockref': weakref.ref(self),
301			'interval': self._lock_renewal_interval,
302			'stop': self._lock_renewal_stop}
303			)
304			self._lock_renewal_thread.setDaemon(True)
305			self._lock_renewal_thread.start()
306
307			def _stop_lock_renewer(self):
308			"""
309			Stop the lock renewer.
310
311			This signals the renewal thread and waits for its exit.
312			"""
313			if self._lock_renewal_thread is None or not self._lock_renewal_thread.is_alive():
314			return
315			logger.debug("Signalling the lock refresher to stop")
316			self._lock_renewal_stop.set()
317			self._lock_renewal_thread.join()
318			self._lock_renewal_thread = None
319			logger.debug("Lock refresher has stopped")
320
321			def __enter__(self):
322			acquired = self.acquire(blocking=True)
323			assert acquired, "Lock wasn't acquired, but blocking=True"
324			return self
325
326			def __exit__(self, exc_type=None, exc_value=None, traceback=None):
327			self.release()
328
329			def release(self):
330			"""Releases the lock, that was acquired with the same object.
331
332			.. note::
333
334			If you want to release a lock that you acquired in a different place you have two choices:
335
336			* Use ``Lock("name", id=id_from_other_place).release()``
337			* Use ``Lock("name").reset()``
338			"""
339			if self._lock_renewal_thread is not None:
340			self._stop_lock_renewer()
341			logger.debug("Releasing %r.", self._name)
342			error = _eval_script(self._client, UNLOCK, self._name, self._signal, args=(self._id,))
343			if error == 1:
344			raise NotAcquired("Lock %s is not acquired or it already expired." % self._name)
345			elif error:
346			raise RuntimeError("Unsupported error code %s from EXTEND script." % error)
347			else:
348			self._delete_signal()
349
350			def _delete_signal(self):
351			self._client.delete(self._signal)
352
353
354			def reset_all(redis_client):
355			"""
356			Forcibly deletes all locks if its remains (like a crash reason). Use this with care.
357			"""
358			_eval_script(redis_client, RESET_ALL)
359			_eval_script(redis_client, DELETE_ALL_SIGNAL_KEYS)
360

ionelmc / python-redis-lock

Lock.release() A last analyzed 2016-10-29 17:21 UTC

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Lock.release() A
last analyzed 2016-10-29 17:21 UTC